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Home My WebLink AboutDENALI VIEW General Information (13)Rick Mystrom, Mayor Municipality of Anchorage Department of Health and Human Services 825 "L" Street P.O. Box 196650 Anchorage, Alaska 99519-6650 Mr. Paul Myers P.O. Box 670351 Chugiak, AK 99567 Dear Mr. Myers: After discussions with Dan Young of Terrasat and Dee Hi and Jim Munter representing you, I ask that you postpone the public hearing for Denaii View Subdivision before the Platting Board scheduled for September 3, 1997. An agreement on a stress test to determine the two existing wells effect on the surrounding subdivisions seems quite possible. With this information, a sound decision can be made regarding this main concern of the neighboring homeowners. I am sure that you, as well as the residents of these subdivisions, have an informed decision as your highest goal. In addition, I will make every effort to educate and coordinate information with neighbors to this subdivision, other interested parties, and other agencies concerning this development. If you have any questions or comments, please contact me at 343-4360. ~) ~,[rely, James Cross, PE Program Manager On-Site Water Quality Mr. Paul Myers P.O. Box 670351 Chugiak, AK 99567 Dear Mr. Myers: After discussions with Dan Young of Terrasat and Dee Hi and Jim Munter representing you, I ask that you postpone the public hearing for Denali View Subdivision before the Platting Board scheduled for September 3, 1997. An agreement on a stress test to determine the two existing wells effect on the surrounding subdivisions seems quite possible. With this information, a sound decision can be made regarding this main concern of the neighboring homeowners. I am sure that you, as well as the residents of these subdivisions, have an informed decision as your highest goal. In addition, I will make every effort to educate and coordinate information with neighbors to this subdivision, other interested parties, and other agencies concerning this development. If you have any questions or comments, please contact me at 343-4360. Sincerely, James Cross, PE Program Manager On-Site Water Quality DRAFT DRAFT DRAFT DRAFT DRAFT Prior to the approval of plat #S-10054 Denali View the Chugiak Conununity Council requests answers and solutions to the following questions and concerns. There arc serious water quality and quantity issues as well as traffic safety concerns that need to be addressed in order for responsible development to occur. The health and safety of existing neighborhoods must be considered. Surrounding ureas and problems need to be looked at when determining what development is appropriate for rural ureas with known problems Denali View platting action- questions from residents to date · =,-1. What will they do about water? ~,,'2. What happens if our wells are drawn down by the new development? ~' 3. What steps are being taken to prevent nitrate contamination in my well from the septics in tile new subdivision? What happens if nitrates show up in my well after the subdivision is built? Who will be responsible? ,,~'5. Will there be plat notes about water quality and quantity issues so that people do not buy in here without knowing what the problems are like I did. · -- 6. If I have well problems after they build above who ,~411 help me? Who is responsible to protect my water? ~7. Are there any rcqnirements to prove that these lots have water before they arc platted? · =, 8. How will all the bedrock affect more septic systems? Are there septic systems that prevent nitrates from getting into our drinking water? ~' 9. Is DEC or MOA responsible for this subdivision when we have problems? i0. Why isn't Seika drive being continued to reach the lots that are fight there? 11. Doesn't new development have to provide safe secondary access for emergency vehicles? 12. What are the requirements for development in these mountainous areas? We have needed another safe way down this mountain for years. 13. What happens when Chugach Park Drives falls offthe side of the mountain and therc is no way for all those families to get home? 14. What happens to tile sledding hill? Does historical use year round prove any type of need or right to the old road? 15. Will tile people and kids on bicycles who have used that access to get to their homes or the park now be on Chugach Park, Kulberg, and Snilins? These roads are narrow and dangerous for people walking and riding bikes. Now we will have the kids sledding on the road! 16. Will these roads be upgraded to handle the additional traffic and make room for the pedestrains who will now be forced out onto the main road? 17. Since the old road has always been access to the top can they just cut it off? Can the city buy the road so we do not lose the access? 18. What is being done about providing another way down tile moantain? Look at how often tile road is blocked and no one on this side of the mountain can get home. 19. Tow trucks have a hard time pulling people back up the cliff when they can't get around them on the mountain. The car that was across tile road with the boat hanging over the cliff is a good exan~ple. 20. Will this mean that the Muni is going to fix our roads and widen them so that people are safe? 21. Does the developer have any responsibility to upgrade the roads to get to tile new lots? 22. If the road is suitable for further development than why can't we get the road widened and improved with guard rails like other area roads? 23. Will buyers be warned about having to walk home up the mountain in the spring when the bottom falls out of Sullins? 24. Does this mean that we will get better roads before someone gets killed? DEC-05-9? FRI 09:29 RE/Nh" *~ EhGLE RIVER Fh× NO, 9076960214 ?,01/01 Decemhor 4, 1997 Jim Cross MOA,DIIIIS At the Tech Board meeting you and Lam mentioned memo's and drafts regarding phase 2 of the nitrate study .I would like to know o,xaetly what is going on, I was told months ago that the con~xact was about to be let anal as yel has not, Why not? What ia going on'? Why has it been d~layed? As you know I hav~ quostlons about Phase I and Phase 2. I haw been wai~lg for die Tech Board w g~t cau~t up ~a ~e ~ls ~ssue up Ibr discussion, I ~ve ou~in~ my Concerns to you on s~veral occasions. I sent you and the Bnard memhar~ a letter la~ Au~ demdbing my quadro ~ co~e~. I ~mod ~t fl~ey n~d~ to b~ ad~s~d at ~o Te~h Eoard, What is the status of phase 2 of the nitrate study? Who will handle it with Mark Little leaving? What are the memos about thal: are not ready for the Tech l~oard to see? I would llke to see any current correspondence lltat relates to tho nitrate study. If you camaot get me ¢opio* of thc correspondence relating to thy questions then please forward on this written request for the tnfomdon to the appropriate person.. Who ts rasing issues and concerns about the project? What are the issues being raised? What is MOA doi~g about it? Has il: been decided not to do Pha~eC? Tile tfitsal~ issue eaxmot bo igxtored. There are probtcms and we need to begin to deal with them. I have been pustung tbr t~s lbr so long and I am frustrated. My questions and concerns mis~i in my August ,q ]otter to you still }rev, not been adds'c~sed. Thc nitxaW issue did not g~t deal[ witl~ a~ Wednesday's meeting and l~as been lelt offthe agenda for next week, It is old business that has not be~n ar. Mresscd. I will bc requesting a work session to got tho nitrate ,mxdy phase i and 2 issue on the robie. Wc emmet ~onl/nu¢ to drag fl~is out. Slk~on Mlnscll P,S. It would be halpful to have a copy of thc MOU with DEC m review borer* we gcC to the m~etlng m~ Wednesday. Is there a:ly hfformation y~:t about how many wells we are talking about? How does the Board respond to Elaine's request to have a position on the trmffer when we do not know anything about it? i hope Art has lots of answers. What ia ~tatus of MOA HAA ordinmtc~? Hope wc can get an update on Wednesday. Rick Mystrom, Mayor Municipality of Anchorage Department of Health and Human Services 825 "L" Street P.O. Box 196650 Anchorage, Alaska 99519-6650 October 10, 1997 Mr. James A. Munter, CGWP Principal Hydrogeologist Bristol Environmental Services Corporation P.O. Box 100320 Anchorage, AK 99510 Dear Mr. Munter: Thank you for your letter of October 8 stating the proposed details of an aquifer test plan for the well on Lot 3 of the proposed Denali View Subdivision. I wish to make the following comments: As I have stated numerous times, I believe the best and most accurate method for determining the affects of the appropriation of water from the proposed Denali View Subdivision on the surrounding properties is an aquifer test involving the existing surrounding wells. I am not prepared to approve a modeling concept at this time, for discussions with homeowners and with Dan Young lead me to believe that the possibility of homeowner participation to a useful degree may still occur. I will make that decision by Tuesday, October 14. I have attached comments by Dan Young concerning your proposed test. I believe very little compromise is needed to conduct a test on Lot 3 that is agreeable to all parties. I request that you read Mr. Young's comments and respond as soon as possible. I realize that time is of the essence, and I will address your concerns as quickly as possible. I am convinced that it is possible to conduct a test on Lot 3 sometime next week (October 13 through 17). Concerning your proposal to prepare a model to determine the affects of the well located on the proposed Lot 9, I cannot approve this plan at this time. Homeowners should reach a decision early in the week as to their participation level, and a meaningful review of that information will determine the path to follow. Again, I urge you to read Dan Young's comments concerning this testing and to attempt to reach a test design that will be a meaningful compromise and will be acceptable to all parties. I will talk to you early next week, and will give you a more definitive decision by Tuesday, October 14. Case S-10054 Denali View Subdivision Platting Board Meeting October 1, 1997 If at the conclusion of the public hearing, the Board approves the preliminary plat, the following conditions are recommended: Approval of the plat subject to: 1. Resolving utility easements. 2. Entering into a subdivision agreement with the DPW for: a. providing improvements on Kullberg Drive, Thornton (Sullins) Drive and Solleret Drive to a rural 24 foot wide gravel standards. b. providing street signs and traffic control devices. c. constructing the trail. 3. Dedicating Kullberg Drive to a 60 foot width. 4. Providing a turnaround at the northerly terminus of Thornton (Sullins) Drive. Resolve the need to dedicate the turnaround with DPW, Traffic Engineering and Transportation Planning. 5. Providing a trail easement on the plat along the west boundary of Lot 11 and extending along the lot line between Lots 10 and 11 to the Kullberg Drive cul-de-sac. Resolve a 12' or 20' width for the trail easements with Division of Parks and with Transportation Planning. 6. Resolving drainage and drainage easements with Project Management and Engineering, DPW. 7. Obtaining ADEC approval for development within this subdivision. 8. Demonstrating that minimum lot area and minimum lot width requirements of the R-10 district based on the average slope of each lot are met with Land Use Enforcement. S-10054 9/3/97 Page 2 10. 11. Resolving with DHHS the need for additinal hydrologic testing or modeling to ensure that the appropriation of water by the proposed Denali~ View Subdivision will not unduly affect the existing surrounding residential wells. Resolving with DHHS the need to place a note on the plat requiring the installation of nitrate reducing septic systems. Correcting street name: Sullins Drive north of Malcolm Drive is now Thornton Drive. 12. Correcting the title block information to read: Grid NW 1261. mro C:\MSOFFICE~WINWORD\WORKFILE\PLATTiNG\97PLAT~10054CO2,DOC Oct-O1-97 01:35P Community Planning & Deve 907-343-4220 P.03 Dellali View Subdivision Case S- 10054 10/1/97 Page 2 June and July, 1997 07/22/97 08/06/97 9/3/97 The applicant completed the following: completion of the hydrology report which was forwarded to thc Chugiak Corr~Bunity Council, tile Municipal DHHS and State ADEC and DNR; · review and discussion of the hydrology repmt at both the June and July community council meetings. Following the July Chugiak Community Council meeting. residents from some of the surrounding subdivisions contracted wiLh a second hydrologist to have another water study performed, The second water study and comments from state agencies arrived shortly before the scheduled August 6, 1997 public hearing. At the request of the petitioner, the case was postponed to September 3, 1997 as only 6 Board members were present of which only 5 could hear and vote on the application. At the request of the petitioner, the ease was postponed to October 1, 1997 £o a.llew time for the hydrologists to establish parameters for additional testing of water availability, DISCUSSION: Throughout the analysis of this plat there have been tltree main issues: (i) water quality and quantity; (2) Wadi'lc circulation, and (3) trail colmections. The trails issue has been resolved. The petitioner will provide a trail connection between Seika Drive a_nd Kullberg Drive which will follow the south boundary of proposed Lot 11, There have been requests from neighbors to provide an easement for a trail coimection from Setka Drive oil the south to Sullins (Thornton) Drive on t_he north which runs along the common lot line between Lots 6 and 7. This trail is commonly referred to as the sledding trail. This ti'all is not on the recently adopted Areawide Trails Plan and t]~ere is no authority to require that this trail 0ct-01-97 01:35P Community Plannin~ & Dev~ 907-~43-4220 P.04 DcnaliVlcw Subdivision Case S-10054 10/1/97 Page 3 easement be provided. The applicant has stated his intention of maintaining this trail as close to the existing alignment as possible. However, the actual trail alignment will depend upon Lhe final plat design givcn thc need to provide for on-site tlti]ities- The final trail alignment is not know~l at Ohs time and easements for the trail are proposed to be recorded by docunlent. St'all' concurs that this is a reasonable alternative. Traffic cir--: The issue o£ a secondary, access has been raised over the last twenty yeaxs and has been raised again with this subdivision, Road cmmections havc suggested /'rom Sollcret Dr/ye to Sullins {Thornton) Drive ~-md Ikom Kullberg Drive to Seika Drive. The Solleret-Sullins route is steeply sloped and it is doubtful that a road could be constr~mted t~ current Municipal standards. The proposed Kullberg-Seika alignment is steeply sloped. Therc is an outcropping of bedrock that would need to be blasted having possible adverse effects on existing hon~es and wells in close proximity to the road. Large amounts of fill would be required to construct the road to municipal standards. Due to the steep grades of Seika Drive, residenls park their vehicles at the north end of the turn a~ld walk to their homes in winter, Given the slope, the question has been raised whether fire trucks could use this proposed rotxtc in winter, Neither Department of Public Works nor Tral'flc Engineering are requesting eil3mr dedication or construction of a secondary access, Traltlc Englnecring has stated that there are limited benefits to be gained from requiring this road collnoctiorl. At the July l Y, 1997 Chugiak Community Council meeting a motion was passed not to support a road connection between Seika Drive and Kullberg Water quality a~:d ouantitv: The proposed subdivision Is located in an area where some of thc surrounding property owners have experienced shortage of water, Initial testing of two wells indicated that there was sufficient water to support the proposed subdivision, But a critical issue is what impact the addition of 11 new wells will have on water availability within the surrounding subdivisions, most nolably Scimitar. Ti%ere is a Municipal consensus that additional testing is needed in order to Oct-01-97 01:36P Community Plannin~ & D~ve 907-343-4220 P.05 Denali View Subdivision Case S-]0054 10/1/97 Page 4 assess water availability and what impact this subdivision will havc on existkxg wells. Since thc developmeilt of the two hydrology reports, there have been on-going meetings Ln an attempt to establish the pa_fanciers lbr additional testing, This cased has been scheduled and postponed several times in order to resolve the issue of water availability. There is a recognized need to conduct additional testing of wells. But the applicant has not brought forward any testing me[hodology that will provide enough data to approve such a water availability test and ultimately approve the subdivision design, AMC 21,75.010 states that the platting authority may approve a preliminary or final plat only ff it fLnds that the plat: 'promotes the public health, safety and welfare," and "furthers the goals and policies of the comprehensive developrnent plan." One of the goals of the comprehensive plan [AMC 21,05) is to 'create a living environment of the highest possible quality based upon comprehensive planning for the population and its growth potential, mad addressing the ecological, economic, health, social, public safety and physical development needs of the municipal area," Water is a critical issue for both the proposed subdivision and for the surrounding neighborhood. The subdivision is proposed in an area where there are known water problems. Although the water problems may not have been quantified and have been described as anecdotal evidence, these statements of water shortages cannot be Ignored. The submittal requirements of AMC 21.15.110,4,b demonstrating an adequate water source have not been met. At this time it is not known whether the subdivision will develop individual or shared wells. And It is not known if the subdivision will affect the water supply of residents down slope. Public health, welfare and safety are basic concerns when reviewing a proposed development, A safe. potable and adequate water supply is fundamental to a healthy community. The responsibility for ensuring adequate water is not limited to the boundary of the proposed plat. The responsibility extends to the surrounding area as well. The availability of water is a fundamental need lbr both Denali View Subdivision and for the neighboring subdivisions. 0ct-01-97 01:36P Con~unity Plannin9 & D~ve 907-343-4220 P.06 Denali View Subdivision Case S- 10054 10/1/97 Page 5 DEPA~RTMENT I~ECOMMENDATION Tile Depar'tment recommends that the plat. be returned for redesign and not be reschedulcd for public hearing until a plan has been developed lbr additional les[lng arid the water testing plarl has becn approved by the Department eF Health and Hurnarl Services, The plan must Include dates for comp]etlon of all, required testing arid submittal of the test results to the Department of Health and Human Serviccs. rare C:\MSOFFICE~WINWORD~,wO R K FI L E\PI~A~I-IN G~97 P LA~P' 10054R4.DOC Oct-01-97 01:36P Community Plannin~ & D~ve 907-343-4220 P.05 Denali View Subdivision Case S-]0054 10/1/97 Page 4 assess water availability and what impact this sl~bdivision will have on existkxg wells. Since thc developmei~t of the two hydrology' reports, there have been on-going meetings Ln an attempt to establish the parmlletcrs lbr additional testing, This cased has been scheduled and postponed several times in order to resolve the issue of water availability. There is a recognized need to conduct additional testing of wells. But the applicant has not brought forward any testing me[hodology that will provide enough data to approve such a water availability test and ultimately approve the subdivision design, AMC 21.75.010 states that the platting authority may approve a preliminary or final plat only ff it fknds that the plat: 'promotes the public health, safety and welfare," and "furthers the goals and policies of the comprehensive development plan." One of the goals of the comprehensive plan fAMC 21,05) is to 'create a living environment of the highest possible quality based upon comprehensive planning for the population and its growth potential, al~d addressing the ecological, economic, health, social, public safety and physical development needs of the municipal area," Water is a critical issue for both the proposed subdivision and for the surrounding neighborhood. The subdivision is proposed in an area where there are known water problems. Although the water problems may not have been quantified and have been described as anecdotal evidence, these statements of water shortages cannot be ignored. The submittal requirements of AMC 21.15.110,4,b demonstrating an adequate water source have not been met. At this time it is not known whether the subdivision will develop individual or shared wells. And It is not known if the subdivision will affect the water supply of residents down slope. Public health, welfare and safety are basic concerns when reviewing a proposed development, A safe. potable and adequate water supply is fundamental to a healthy community. The responsibility for ensuring adequate water is not limited to the boundary of the proposed plat. The responsibility extends to the surrounding area as well. The availability of water is a fundamental need lbr both Denali View Subdivision and for the neighboring subdivisions. MUNICIPALITY OF ANCHORAGE Department of Health and Human Services P.O. Box 196650 Anchorage, Alaska 99519-6650 Date: To: From: Subject: Zoning and Platting, CPD James Cross, PE, Program Manager, On-Site Water Quality S-10054 Denali View Subdivision Following the submission of my July 25 memo regarding the Denali View Subdivision, a great deal of information has been assembled and submitted by various agencies and members of the public. Review of this information has generated questions concerning the affects of the development of this subdivision on the wells of the existing surrounding homes. The original aquifer tests conducted on the wells in Denali View Subdivision did show that adequate water could be produced within the subdivision to support the requirements of the subdivision. Due to the concerns of agencies and homeowners alike, efforts have been made to define additional pumping tests on the two existing wells in Denali View Subdivision. These additional tests will monitor the affects of long term water usage by Denali View Subdivision on the existing wells on surrounding properties by modeling this long term usage in a short term pumping test. In addition, a third well has been drilled within Denali View Subdivision to be used as an observation well during the additional pumping tests. Currently, evaluation guidelines are being developed to determine the rules for evaluating the testing prior to starting the test. The results and conclusions drawn from these tests will be forwarded as soon as possible. Tuesday, September 23, 1997 12:54 PM To: ~ross From: Jeff r" Williams Page: 5 of 6 HYDROLOGICAL TESTING PROGRAM FOR DENALI VIEW SUBDIVISION The Municipality of Anchorage has requeszed that additional information be collected in order to make a better infofmed decision about Denali View Subdivision. The following questionnaire will be used to help determine the number of residents in surrounding Subdivisions who would be wilting to participate in a testing program for Denali View Subdivision, The questions are designed to help the hydrologist determine the feasibility ced logistics of the testing program, Tl~e success of the testing program very much depends on the cooperation and involvement of the surrounding property owners. Please answer the following questions, The questionnaire can be returned by faxing it to one of the following numbers: 686-1238 or 344-1383. No cover sheet is required, Or you may call 688- 1236 or 34441386 and we wlll send a courier to pick it up, We would appreciate a response by Thursday, September 25th. 1) Name: Phons; 2) Physical Address: 3) Legal Descriptiom Lot Block Subdivision 4) Do you have more than one well on the property? Yes No 15) If yes, do they both have pumps in them and are they both being used? 6) Do you hays a holding tank7 __ Yes No Size 7) Do YOu know any of the following ~lbout a) Depth of Well feet b) Rata of recovery or yield __ gpm c) What depth is your pump set at? __teat 8) Would you be willing to let the water level in yo~Jr well be monitored? Yes No 9) Would YOu bo willing to go a day or more without pumping your well? Yes No 10) How many days? --__ I day __ 5 days __ 2 days 6 days --. ;3 days 7 days 4 days Gallons 11) What days of the week are best for you not to pump your well? 12) How many people use your well on a daily basis? 13) Are you willing to participate in the testing program if your well pumping can be scheduled and monitored to minimize impacts on you and still provide useful data for the test? __Yes No 14) Would'you be willing to sign the enclosed Hold Harmless Release? Yea No If you have concerns or revisions that you would like to see concerning the Hold Harmless Release, please write tile changes on the form. Tuesday, September 23, 1997 12:54 PM To: Dross From: Jeff L William9 Page: 4 of 6 IN CONSIDERATION of hold harmless release and other consideration described below do hereby agree as follows: FOR AND IN CONSIDERATION of the sum of One Dollar ($1.00) and other good and valuable consideration, the receipt of which is hereby acknowledged, ."Releasers' individually and for their heirs, executors, administrators, successors in interest, trustees and assigns, have released and do hereby release and forever discharge and hold harmless Bristol Environmental Services Corporation, Jim A Munter, DHI Constructing Engineers, Dee High, Michelle E. Myers, Paul V. Myers, Arleen E. Myers, MM&M Contra~ing Inc. and Skyline View ][nc. and their successors and assigns, heirs, personal representatives, and vessels from all aeti~, c,%Os~.s_of.~c~ion~ suite& eontro~'arsii~fi; claims~' ~geS"i'~-~d ~emand~s 6~ ~:~ve~jl~in--~"~'~'x~t~ and for and by reason of any claims demands, injuries, damages and complaints accrued or hereafter to accrue, arising out of any and all aspects of hydrology study, well static level and flow tests for Denali View Subdivision and your well located at except for negligence. ~, This HOLD HARMLESS RELEASE does not and is not intended in any way to affect releasers water rights. understands that this agreement is voluntary and acknowledge that they have had an opportunity ob obtain legal counsel before signing in regard to this HOLD HARMLESS RELEASE and further declare that the terms of this HOLD HARMLESS RELEASE have been carefully read and are now fully understood and voluntarily accepted for the purpose written above. This HOLD giARMLESS RELEASE centains thc ENTIRE AGREEMENT between the parties hereto and the terms oftha r~lease are contractual and not a mere recital. WITNESS our hands on the dates below written Date Date Date Witness Date Municipality of Anchorage P. O. Box 196650 Anchorage, Alaska 99519~665~ (907) 343-4215 FIRST CLASS }{AIL S-10054 NOTICE OF PUBLIC HEARING - - WEDNESDAY OCTOBER 1, 1997 The Municipality of Anchorage Platting Authority will consider the following: CASE: PETITIONER: REQUEST: S-10054 DENALI VIEW SUBDIVISION Skyline View Corp. To subdivide 1 tract into 11 lots. 8ECF_iVED · UUNIL;~&.ffv L~' ~u~urlUHAGE PLaNNiNG &:ONIN¢ OlV~ION September 13, 1997 As msident's of this mountain commlmity we have personal knowledge of Scimitar's water quality and quantity problems and the heartaches they have caused. We have known many of the families who have been financially devastated due to quality or quantity problems. While the Terrasat report pro'4des substantial hard documentation and scientific conclusions, it does not identify many homes ~vith water problems on a seasonal basis, (November-March). There is no way to document what the residents deal with when it comes to seasonal water problems. The available documentation from MOA and residents regarding nitrates cannot be ignored. Scimitar has problems. Ne~v development on top of Scimitar will make the problems worse for Scimitar and most likely have negative impacts on Denali Vie~v. The existing and proposed subdivisions must be protected. Prelhninary plat approval for Denali View should include plat notes requiring public or hanied water and septic systems that provide substantial nitrate reduction due to existing documented problems.. Additionally, the upper trail that follows the original road should be platted as a pedestrian access in it's current location OR the developer provide similarly developed access in another location to be determined before the final plat is approved. Why should tile community give up existing access they have had for 20 years on the original roadbed? Tile Seika-Kniberg connection nmst be addressed for the long-term safety of this commmtity. There is no intent to have a road placed in this location unless access to the upper motmtain is permanentiy blocked. A pedestrian trail only along file existing alignment of the original road bet~veen Kulberg-Seika with a ROW when and if needed solves all the issues. Developlnent of this property will help to bring a stop to the illegal snow machine traffic in the winter that historicalh' access's the State Park via the existing road/trail. Residents ride miles from subdivisions across the highway to access the purk via this road/trail. It ~vould be most helpful if Board members would come out and take a look at this proposed dcx elopment ~md where the proposed Seika~Kulberg easement is plammd. Surely file developer would provide pcrmission for the Board to cross the no trespassiog signs. Possibly Board members will have ideas abou! bow to get tile motmtam children 1o fl~e bus stops in Scin'dt,'u' without the existing road/trail access. Tim. Sharon aud Tmvis Minsch PUMP TEST PROCEDURE FOR DENALI VIEW SUBDIVISION W.O. 96298 Date: 9-3-97 OBJECTIVE: 1) Meet the objective of 21.15.110.B.4.b. To substantiate the availability of a safe and adequate volume of water for domestic purposes. 2) Show now substantial effect on the surrounding neighborhood. CRITERIA 1) Test should be conducted using "established engineering practices". 2) Test should be scientifically sound results so that other agencies, practitioners or boards can rely on the results. 3) Criteria for evaluating the test results should be clearly defined. TEST PROCEDURES A) Lower Well (Sand & Gravel Aquifer) 1) Pump the well at 15 to 25 gallons per minute for 24 hours. This is 16 to 26 times greater than the average flow rate that the well will ever experience. This portion of the test will validate objective # 1(to substantiate the availability of an adequate supply of water. 2) Monitor existing well in the surrounding neighborhood that are in the same static water level zone. This assumes that the wells are hydraulically connected and therefore pump test should show some effect on the monitoring well. This portion of the test should allow conclusions to be drawn about the potential effect on the surrounding wells. Wells on other static water levels should not be effected since they are presumably not hydraulically connected. B) Upper Well (Bedrock Aquifer) 1) Pump the well at 1.5 to 3 gallons per minute for 24 hours. This is 2 to 3 times greater than the average flow rate that the well will ever experience. This portion of the test will validate objective # 1(to substantiate the availability of an adequate supply of water. 2) Monitor existing well in the surrounding neighborhood that are in the same static water level zone. This assumes that the wells are hydraulically connected and therefore pump test should show some effect on the monitoring we~L This portion of the test should allow conclusions to be drawn about the potential effect on the surrounding wells. Wells on other static water levels should not be effected since they are presumably not hydraulically connected. DISCUSSION 1) Wells within 1000 feet of the subject well that are within the same static water level need to be verifiably shut down for several days before, during and after the test. This is to allow the aquifer to recover to near static conditions before the test begins, to prevent uncontrolled pumping of the aquifer during the test and to allow for accurate data collection during recovery. This should result in data from which valid conclusions can be drawn. 2) Further testing needs the cooperation of the adjoining neighbors. Lots adjoining the subdivision need to have their wells test pump prior to and during the flow tests of the subject wells. These tests need to be conducted in accordance with DHHS test procedures for Health Authority Approvals under the direction of a Professional Engineers. This will help quantify the number of wells that are below the Municipal Standard before the test and it should help to answer questions about the effect of the subject wells on adjacent lot owners that are not hydraulically connected. 3) By limiting the well to a 24 hour test, we have a much better chance of getting the cooperation of the neighbors. Their well will need to be down for a much shorter time (approximately five days). 4) The test doesn't over stress the aquifer to the point that recharge becomes a problem in the evaluation of the aquifer. The 24 hour test is standard practice. 5) The flow rates suggested should not damage the sand and gravel aquifer by over pumping. It is very likely that the higher rates of pumping (70 gpm) that have been suggested will permanently damage the well. 6) The data collected from the above test will be technically sound. Strong conclusion can be drawn from the data. Departments, Agencies, and Boards should be able to rely on the information to make informed decisions. EFFECTS ON SURROUND PROPERTY WELLS What is the criteria for evaluating the effects of pumping on adjacent property owners? The standard for the Municipality is defined as "substantial". I assume that substantial would mean that the results clearly show that wells in Denali View reduce the supply of water available in the aquifer such that neighboring well production rates fall below the minimum standards of MOA and that effects must be felt by substantial number of the property owners and that the existing well owners cannot reasonably obtain the water by drilling deeper or by hydrafacturing. Therefore, having an effect on two or three wells wouldn't constitute a substantial effect unless it can be shown that there is a water shortage the aquifer. If the homeowner can reasonably drill deeper or hydrafacture his well and still obtain water then he has not been substantially effected. This definition will coincide with current state law. It is presumed that all property owners have a right to water within an aquifer as long as there is an adequate supply of water. It is presumed that as long as there is water available, then it is reasonable to expect existing well owners to deepen or hydrafract their wells inorder to access the water, Denali View Subdivision Case S- 10054 Meeting of August 13, 1997 Agenda Water availability a. Two hydrology reports Water quality a. Nitrates Detaile' Pumping Test to Characterize a Fractured Bedrock Aquifer a . b by Jeffrey D. Gernand and Jeffrey P. He~dtman Abstract Bedrock fractures and results of a 24-well, 21-day pumping test were analyzed to characterize a low-yielding fractured gneiss aquifer. Several analytical techniques for evaluating aquifer tests in fractured bedrock are reviewed and applied. The time-drawdown curve for the pumping well and the early time-drawdown responses at several nearby observation wells indicate linear flow through a single fracture. In contrast, analysis by radial flow techniques of the late time-drawdown responses at all observation wells suggests that flow occurs through interconnected fractures. Taken together, these time-drawdown responses are consistent with a model incorporating linear (single fracture) flow at the pumping well and radial (interconnected fracture) flow in an outer region. The elliptical cone of depression reveals a direction of enhanced drawdown which closely parallels one of five observed fracture sets. However, this fracture set comprises fewer than 15 percent of all fractures present. The drawdown response should not be extrapolated to characterize the entire aquifer, because it does not result from an overriding structural feature which would influence the aquifer-w/de hydraulic response. The results indicate the advisability of performing structural analysis along with aquifer analysis to characterize a bedrock aquifer. Further, the results indicate that in an aquifer where the hydraulic response at a pumping well suggests linear single fracture flow, if more obsevation wells or later time data are available it may be found that the aquifer responds with radial flow. The results also suggest that in certain bedrock aquifers, the larger the area of investigation, the more likely the aquifer will be shown to behave consistently with radial flow analytical techniques. In order to obtain the appropriate data, the goals of a bedrock pumping test and the structural data should be carefully considered before the test duration and observation well network are planned. Introduction Pumping tests are sometimes proposed to characterize a bedrock aquifer. No analytical method can be universally ap- plied to fractured bedrock pumping test results (Walton, 1991), and economic constraints generally limit the number of observa- tion wells and the duration of the test. Perhaps as a consequence, convincing field examples of thoroughly characterized bedrock aquifers are lacking in the literature (Walton, 1991). Drawdown contour maps are frequently used to evaluate anisotropy, and may sometimes be used to make predictions regarding ground-water flow elsewhere in the aquifer. In this paper it is assumed that in order to generalize the results of a pumping test to regions beyond the tested area, there must be a strong correlation between the drawdown contours and the geologic structure. If there is a direction of maximum draw- down, it must correlate to the orientation of a dominant trans- missive fracture set or intersection of sets, to allow the conclusion that similar drawdown would also occur in regions beyond the tested area. Presence of these dominant transmissive fractures could impart hydraulic anisotropy to the formation on a large scale. Time-drawdown data from individual wells are also typi- cally evaluated for most bedrock pumping tests. There are sev- aGannett Fleming, Inc., Suite 200, East Quadrangle, Village of Cross Keys, Bat more, Maryland 21210 bF · . uss & O'Nedl, Inc., 146 Hartford Road, Manchester, Connecti- cut 06040. Received March 1995, revised January 1996, accepted October 1996. 632 eral analytical models that can be used to evaluate fractured bedrock pumping test data. A given set of pumping test data may sometimes be equally wellinterpreted by several dtifemnt models (Gringarten, 1982). Equivalent porous medium (EPM) models (Schmelling and Ross, 1989; Pankow et al., 1986; Long et al., 1982) assume that at the scale of interest the fractured aquifer behaves identically to an unconsolidated medium. If a bedrock aquifer can be characterized as an EPM, then pumping test data may be interpreted by methods such as Theis curve matching. Single fracture models (Gringarten and Witherspoon, 1972; Gringarten, 1982; Karasaki, 1986) consider the pumping well to be intersected by a single fracture that is significantly more transmissive than the rest of the aquifer (Figure la). These models characterize that fracture based on drawdown data from the production well that typically plots as a straight line on a log-log scale at early time, merging with a Theis curve tithe test is sufficiently long (Figure lb). Drawdown in observation wells beyond the elliptical zone of linear flow may be interpreted by radial flow methods for large distances or after long periods of pumping. The single fracture itself is sometimes referred to as an extended well (Jenkins and Prentice, 1982). The double porosity approach (reviewed by Moench, 1984 and Streltsova, 1988) characterizes the fractured aquifer as two components: high transmissivity, low storativity fractures, and low transmissivity, high storativity rock blocks (Figure lc). In the classic double porosity response, the early and late time-drawdown data plot on separate Theis curves (Figure ld) connected by intermediate time data correlating to the beginning of flow out of rock blocks into the fractures. Very early time data at the pumping well may plot linearly as single-fracture flow (Streltsova, 1988) if not ob- scured by wellbore storage effects. Vol. 35, No. 4--GROUND WATER--July-August 1997 hD lb hD 1.0 O.S ld Vet,. ~1 Fracture Curve Theis Cu/ve tD s °;°o~ /,/. ,~ ....J _~ ,~ tD/r2D Fig. 1. Comparison of conceptual geologic models for bedrock ground-water flow and their respective type curves for pumped wells. la/lb~Single fracture model (after Jenkins and Prentice, 1982) and a type time-drawdown curve in the production well with early time linear response and late time Theis response (after Gringarten and Witherspoon, 1972). lc/ld~Double porosity model (after Streltsova, 1988), and type time-drawdown curves with various fracture skin factors (after Moench, 1984). Project Considerations An incinerator ash iandflll was proposed on a 30-acre site overlying metamorphic bedrock in eastern Connecticut. Siting policy dictated that the area of influence of any potential leach- ate plume be predicted before disposal, and given the thin over- burden at the site, it was recognized that the bedrock aquifer could be impacted by a leachate release. With the above models as a backdrop, an evaluation of ground-water flow within the crystalline bedrock was undertaken using structural analysis and an extended aquifer test. A number of observation wells at a variety of distances and azimuths from the pumping well were used, and an indefinite pumping period was planned. Site Description At thesite, bedrock is mapped as a fine to medium-grained equigranular gneiss (Goldsmith, 1967). Geologic mapping indi- cates a consistent foliation attitude approximately N70W, 55NE, with no folds or faults mapped within 2000 feet of the site (Goldsmith, 1967). This trend is conformable to regional folia- tion (Goldsmith, 1985). Site-specific observations were consis- tent with the published descriptions, except for the identification of a more marie lithotype that occurs in 1 to 10-foot thick layers parallel to the foliation. This lithotype is fine-grained, more easily weathered than the granitic gneiss, and appears to consti- tute 5 to 15 percent of the rock. Piezometric measurements at 40 bedrock observation wells revealed that the bedrock aquifer has a hydraulic gradient which ranges from 0.16 to 0.32 ft/ft, closely mirroring the surface topography and suggesting low overall transmissivity. Yields estimated during drilling ranged from 0.25 to 18 gallons per minute (gpm) for the 6-inch bedrock wells, with an average estimated yield of 5 gpm. Seven of the wells have been pumped for periods of one to four hours, with yields ran~ing from 2 to 8 gpm (specific capacities of 0.01 to 0.67 gpm per foot of draw- down). A borehole geophysical investigation consisting largely of fluid and rock resistivity, temperature, and sonic logging indicated that in each 6-inch bedrock well (up to 305 feet deep) there were from one to seven producing zones. This was gener- ally consistent with the logs for the wells, which showed on the average one producing zone (greater than 0.25 gpm) per 40 feet drilled. On-Site Fracture Orientations--Core Data Rock cores from MW-13B, MW-23B, and MW-30B2 (see Figure 2 for locations) were selected for intensive inspection and fracture analysis. In all, 98 feet of rock core were inspected, including 60 feet at MW-30B2. A total of 215 fractures were analyzed. RQD ranged from 0 to 100, with an average of 63. Fracture density diminished only slightly with depth. Because the cores were not oriented, all fracture orientation measurements in rock core were based on a comparison, to the orientation of the foliation. Two critical but apparently valid assumptions were made in order to obtain accurate fracture orientations from rock core: (1) no faults or folds are present, and (2) the foliation has a consistent orientation. In addition to the fact that no folds are mapped within 2000 feet of the site (Goldsmith, 1967), in over 250 feet of rock core, nearly 1700 feet of downhole video imagery, and in on-site outcrops no faults or folds were observed. Published orientations of foliation in the vicinity (Goldsmith, 1967) are very consistent. Twenty-four mea- surements of foliation in an outcrop 500 feet northwest of the pumping well PW revealed an average strike of N60W, with a Fig. :2. Site map, drawdown contours, and fracture rose. The fracture rose is based on a weighted average of 157 fractures measured in rock core and 80 fractures measured in outcrop. standard deviation of 6 degrees. Average dip was 58 degrees NE, with a standard deviation of 5 degrees. Based on these data, it appears that local variations in deformation are not significant. Each fracture was classified in terms of apparent hydraulic significance based on criteria adapted from Jones et al. (1985). X-type fractures are those that appear to be major flow channels, with deep weathering of the fracture surface. A-type fractures include those that appear to be open to water flow but show little or no weathering on portions of the fracture surface, and frae- tures that have locally measurable aperture (greater than 1/32#), but that remained unbroken in the core sample. B-type fractures include those that are mineralized, limiting present- time flow but indicating past flow. C-type fractures are those that remain unbroken in the core sample and show no visual sign of weathering. A total of 15'~, ,xes to X- and A-type fractures were plotted on an equal area net. The distribution of poles was contoured (Figure 3a), based on guidance provided by Billings (1972). There are three predominant sets of X- and A-type fractures present in the rock cores. One set parallels foliation with an average atti- tude of N60W, 58 NE, and comprises 28 percent of fractures. Another set comprises 23 percent of fractures and has an average attitude of NSOE, 43 S. A third set comprises 16 percent of fractures and is essentially fiat-lying, with an average attitude of N80E, 2 S. Approximately 33 percent of the X- and A-type fractures in the rock cores do not fit into any fracture set. On-Site Fracture Orientations--Outcrop Data Fractures observed in recently exposed outcrop were used to compensate for the inherent bias against steeply dipping fractures in rock cores. Two 30-foot transects trending N20W and N40E along outcrops located 600 to 700 feet northwest of the pumping well (PW) were established, and all visible fractures along each 30-foot horizontal transect were measured. In addi- tion to the two outcrop transects, an outcrop was uncovered 200 feet northeast of PW during excavation for the landf'fll. Although too small to establish a transect, this outcrop was so close to PW that all 10 visible fractures were measured and added to the outcrop fracture data base. There was no dominant fracture set in this outcrop. Based on these observations, poles to all 80 measured out- crop fractures were plotted on an equal area net and contoured (Figure 3b). Three predominant sets of fractures were identified in outcrop. Approximately 38 percent of fractures measured in outcrop do not belong to any of these defined fracture sets. Structural Synthesis Outcrop data depict the distribution of steeply dipping fractures at the site, while core data depict gently dipping frac- tures. Each data set has three primary fracture sets. The only CONTOUR 01AGRA~ OF POLES CONTOUR DIAGRAM OF POLES TO BOREHOLE TO BOREHOLE X- AND A- POLES TO OUTCROP X-~PE FRACTURES ~PE FRACTURES FRACTURES ~i[. 3. ~1 ~i~sr~m~ of pole~ to ~eture pl~,e~. ~eteent~le of tot~l fr~ctu~e~ me~ure~ ~d ce,frei tende~c~ for e~eh fracture ~et ~re li~ted. 3~-- Contour ~i~m ofpole~ to ]~? X- ~,d A-type f~cture~ measured 1~ ~ock eore~. ~b-- Contour ~i~lr~ml of pole~ to 80 1, outcrop. Note that the N4W. 86~ f~etu~e ~et plo/~ i, t,o lutetium o, the ~tereo~m due to ~dom ~ri~tiom i~ dip ~ f~cture ~et. 3e--~i di~m of pol~ lo ]~ X-~pe ft~ct~ me~u~ed 1, ~ock core. Note that the ~ro~p of ~ pole~ to foli~tion-p~llel fr~ctur~ the lo,et left of Jc i~ ~,ei~ll? clu~tered due to the ~umption that ~11 foliation ~e~ N~0~. I~ outcrop foliation ~ke measu~ement~ bad 634 Table ,ummary of Well Construction and Pumping Test ,~esults Distance Early Total Bedrock Diameter Depth from Type tirne Lag Theis drawdown well (inches) (ft) P IV (irt) curve slope: time ~ lag3 Oft) PW 6 303 0 Linear 0.3 0 NA · 170.55 8B 6 67 145 Theis NA 30 30 4.87 13B 2 65 275 Jacob 1.0 300 NA 1.61 17 6 200 250 Theis NA 150 150 5.57 18B2 2 32 320 Jacob NA 18,000 NA 0.12 23B 2 42 50 Jacob 0.7 80 NA 0.61 23D 6 301 60 Hantush4 NA 50 50 2.59 29B 6 62 85 Theis 1.6 3 150 10.38 29D 6 302 85 Theis 1.7 4 50 7.90 30B 2 37 100 Theis NA 4,000 4,000 1.47 30B2 2 80 110 Jacob NA 800 NA 0.26 32B 6 101 130 Hantusha NA 40 40 6.16 32D 6 301 130 Hantush4 1.4 I 30 21.59 33B 6 102 37 Theis 1.2 1 60 10.38 33D 6 305 37 Hantush4 1.2 0 0.3 Defined as straight-line segments on log-log plots, slope = log cycles of drawdown/lo,, c,,cle of tim~ ,.fA. 4. . . 19 ~ -, ~. ~,'~ mmcates no early time drawdown, or early time slope did not deviate from the matched type curve. Unul drawdown begins, in m nutes. Until drawdown is matched by a Theis or Hantush curve, in minutes. nHantush type curves for leaky aquifers. fracture set that may be common to both outcrop and core data is the set trending N60W, 58 NE in core and N65W, 70 NE in outcrop, approximately parallelling foliation. The remaining four identified fracture sets are clearly dissimilar. The two addi- tional sets observed in outcrop are steeply dipping and therefore woul.d be underrepresented in the core data. One set observed in core is nearly horizontal and therefore would be underrepre- sented in outcrop. Based on the available data, it appears that all five fracture sets are present in the rock matrix in the area of the pumptng test. Considering only X- and A-type fractures in cores and all fractures in outcrop, no fracture set comprises more than 28 percent of total fractures measured. Fracture density is greater than one per foot in cores; this combined with the variety of fracture orientations leads to a high degree of fracture intercon- nection in the aquifer. However, if a single fracture set were to be hydraulically dominant, it was expected to be the foliation- parallel set. Approximately 66 percent of the X-type fractures in cores, the apparent mai or flow channels, were from this fracture set (Figure 3c). The pumping test was designed to determine how the struc- tural geology affects the hydraulic response. The structural data led to two principle working hypotheses. The first held that the aquifer could be characterized by radial flow via interconnected fractures, while the second held that the foliation-parallel fea- tures would control the hydraulic response during pumping. Pumping Test A six-inch diameter, 303-foot deep open hole bedrock pumping well PW was installed in proximity to a number of bedrock observation wells (Figure 2). The location was chosen to be along foliation strike from four nearby observation wells, and along strike of the N80E, 43S fracture set from four other observation wells. This alignment was proposed to promote the probability of measuring enhanced drawdown along the strike of one of these fracture sets. On the other hand, the cluster of wells around the pumping well allowed measurement ofdrawdown in many directions, allowing determination if the aquifer could be evaluated as an isotropic EPM. During a three-day background period and throughout the test, water levels were measured continuously at PW and 23 observation wells, including several overburden and remote background wells not shown in Figure 2. The pumping test lasted for 21 days at an average yield of 6.5 gpm, ranging from 6.0 to 7.2 gpm. Yield declined slightly as drawdown increased. After 21 days, the shape of the drawdown contours had stabi- lized (Figure 2). All 14 of the bedrock observation wells within 300 feet of PW experienced drawdown during the pumping test. A summary of the key information pertaining to these wells can be found in Table 1. Discussion/Analysis--Relationship of Drawdown to Fracture Patterns Drawdown contours were mapped for both the shallow and deep bedrock zones and found to have similar configurations (Fuss & O'Neill, 1991). For ease of presentation, these results were composited and presented as a single cone of depression (Figure 2), in essence showing flow in the aquifer as two- dlm. ensional (horizontal) with vertical flow components regarded as inconsequential relative to the goal of predicting the area of potential plume influence. The cone of depression in Figure 2 is elongate along a N86E trend, essentially parallel to the strike direction of two fracture sets. The hydraulic response at the pumping well is controlled either by a master fracture belonging to the N80E 43S set, or by the intersection of fractures of that set with the fractures of the NSOE 2S set. The NSOE 2S fracture set alone is not likely responsible for the drawdown development, because that set is essentially flat-lying and would have produced more circular drawdown contours. Drawdown was measured in all wells within 300 feet of PW, and this along with consideration of fracture observations indicates that fractures are well- connected spatially at the scale of the test. Neither of the two principal hypotheses based on structural control of ground-water flow were completely supported by the observed drawdown. In the first hypothesis, relatively circular drawdown contours deriving from radial flow via diversely oriented interconnected fractures should develop. In the second hypothesis, elongate drawdown contours parallel to the N60W trend of the foliation should develop. The data suggest that (1) at the scale of the well, ground-water flow is likely governed by a master fracture (extended well) striking approximately N86E, and (2) at the scale of the test the aquifer is heterogeneous and flow occurs through diversely oriented interconnected fractures. The results of this test cannot be extrapolated to characterize other regions within the aquifer because of limited correlation with a dominant structural feature. Aquifer heterogeneity inval- idates both principle hypotheses of structurally controlled ground-water flow at the scale of the aquifer. Discussion/Analysis--Evaluation of Time-Drawdown Curves The timc-drawdown data for PW display an approximate slope of 0.3 log cycles of drawdown per log cycle of time up to 3000 minutes (Figure 4a). The data after 3000 minutes are not amenable to analysis due to periodic pump adjustments to main- tain flow rate as drawdown increased. This drawdown curve cannot be matched to a Theis curve or other radial flow solution. Overall the PW drawdown curve is consistent with linear flow in a single fracture or fracture set which is significantly more transmissive than the remaining fractures. Wells with single fracture flow typically have drawdown curves consisting of straight lines with slopes of 0.25 to 0.5 (Streltsova, 1988). A slope of 0.25 would be attributed to a relatively low-permeability master fracture, while a slope of 0.5 would be attributed to a high-permeability fracture (Gringarten, 1982). The early time-drawdown data for observation wells near PW cannot generally be matched to a radial flow solution such as a Theis curve. Where early time deviations from Theis type curves occur, the data can be instructive in evaluating a pumping test where flow at the pumping well occurs dominantly through a single fracture or extended well. Wells that intersect the extended well should have a drawdown response similar to that at the pumping well, or identical if there is no well loss (Jenkins and Prentice, 1982). If the early time data have a lower slope than the Theis curve but greater than the pumping well (Figure 4b), it indicates that the observation well is in proximity to the master fracture but does not intersect it (Krnseman and de Ridder, 1991). Interpreting the early time-drawdown data for MW-29B, MW-29D, and MW-32D with type curves and formulae pre- sented by Kruseman and de Ridder (1991) suggests the extended well at PW is 140 feet long (Figure 2). At this site, all observation wells within 50 feet of the interpreted extended well have early time-drawdown curves that deviate from the Theis solution, indicating they have an early phase of linear flow. All wells greater than 50 feet from the extended well have early time data amenable to radial flow solutions (Table 1), with the exception of MW-13B. The late time-drawdown data for all bedrock observation wells within 300 feet of PW were interpreted by radial flow methods, as is appropriate for wells outside the zone of linear flow after long periods of pumping (Jenkins and Prentice, 1982). This indicates that at that scale the aquifer is characterized by spatially well~connected fractures. Most of the observation well responses were matched to Theis curves (Figures 4b and 4c). Late time Theis curve matches are typical of observation wells responding to pumping from an extended well (Gringarten, 1982). Based on the drawdown curves, the single fracture model appears to be an appropriate model for this aquifer test. The aquifer test is dominated by linear flow in a single fracture at PW extending approximately 140 feet in an east-west direction. Con- sistent with the single fracture model, at the observation wells radial flow through interconnected fractures dominates after the first hours of the test. Implications for Smaller Scale Pumping Tests The abundance of data collected allowed a detailed por- trayal of the bedrock aquifer at this site. However, a typical pumping test would not be nearly as long, nor would there be as many observation wells. Some of the data collected highlight how a smaller scale test may have provided an erroneous aquifer characterization. In many crystaLUne bedrock aquifers character- ized by fracture flow and minimal primary porosity, it is likely that pumping wells will obtain water from relatively few fracture zones. It is typical practice to complete a well after a single moderate- or high-yielding fracture is encountered, with addi- tional drilling only to add storage to the well. Due to economic constraints, the observation wells for a pumping test are typically Time (min.) Fig. 4. Time-drawdown curves for the pumping well PW (4a), and observation wells MW-29B (4b) and MW-17 (4c). few and the aquifer tests of limited du, .on. A test with only three observation wells would possibly have revealed the same orientation for the extended well, but would have failed to show the degree of interconnection at all azimuths. Time-drawdown curves developed from an 8-hour or even 72-hour test may have suggested a strictly linear flow domain, because the early time data at many wells suggest linear flow. Although drawdown in most wells was matched to a radial flow type curve after the first 150 minutes of the test, it takes approximately two log cycles of time thereafter to correctly identify the type curve. With less time the later time-drawdown data may also appear to plot linearly. It is vital to characterize the geology and define the goals of the pumping test before completely planning the observation well network and test duration. In planning a test to demonstrate the behavior ora bedrock aquifer, as opposed to the behavior of a single well, one should consider detailed structural analysis, a more elaborate observation well network, greater pumping duration, and more comprehensive analysis of drawdown Conclusions The pumping test and structural analysis reported herein are based on abundant data, and different portions of the data set when viewed independently support different aquifer charac- terizations. Fracture analysis revealed five fracture sets of var- ious orientations, with no fracture set comprising more than 28 percent of fractures; these observations suggest that radial flow may develop via intemonnected fractures. However, one fracture set parallel to foliation included 66 pement of the fractures inferred to be highly transmissive in rock core (Figure 3c); if the aquifer could be characterized as anisotropic, the direction of maximum drawdown was anticipated to be parallel to this frac- ture set. Drawdown was experienced in all directions from the pumping well and at all wells within 300 feet, suggesting radial flow in an intemonnected fracture matrix. For the observation wells experiencing drawdown, ali time-drawdown curves could be interpreted by radial flow techniques. However, time- drawdown data from the pumping well and early time-drawdown data from the observation wells within 50 feet of the extended well suggest linear flow in a single fracture. These observations in sum am consistent with the single fracture model, where radial flow dominates outside the area immediately around the master fracture intersecting the pumping well. Drawdown contours (Figure 2) support the model. The axis of maximum drawdown does not parallel the most abundant fracture set, demonstrating the limited correlation between the hydraulic response observed during the pumping test and the major structural features. The elongated drawdown contours observed at PW cannot be extrapolated to characterize the entire aquifer, Taken in context with the available geologic data, the pumping test portrays an aquifer that is heterogeneous and composed of many intercon- nected low-permeability fractures in a relatively impermeable matrix. The r~sults indicate the advisability of performing structur- al analysis along with aquifer analysis to characterize a bedrock aquifer, particularly_ ,ow-porosity crystalline bedrock where a single fracture zone may yield most of the water to a well. The results also indicate that, while response at a pumping well may suggest linear single fracture flow, ff more observation wells or later time data are available it may be found that the aquifer responds with radial flow. The goals of a bedrock pumping test and the structural data should be carefully considered before the test duration, observation well network, and data collection and analysis programs are planned. Acknowledgments We thank Dr. Paul Hsieh and three anonymous reviewers, along with our colleagues Robert S. Potterton, Jr. for his review of previous drafts, and Arthur Zahradnik for his review of the discussion of time-drawdown curves. References Billings, M. P. 1972. Structural Geology. Prentice-Hall, Englewood CIiffs, NJ. Fuss & O'Neill, lnc., 1991.21-day Bedrock Pumping Test, Potential Residue Disposal Site, Fort Shaatok Road. Goldsmith, R. 1967. Bedrock Geologic Map of the Uncasville Quad- rangle, Connecticut. Reston, VA. U.S. Geological Survey Map GW-576. Goldsmith, R. 1985. Honey Hill Fault and Hunts Brook Syncline. Guidebook for Fieldtrips in Connecticut and Adjacent Areas of New York and Rhode Island. State Geological and Natural History Survey of Connecticut. Guidebook no. 6, pp. 491-507. Gringarten, A. C. and P. A. Witherspoon. 1972. A method of analyzing pump test data from fractured aquifers. In: Int. Soc. Rock Mechanics and Int. Ass. Eng. Geol., Proc. Syrup. Rock Mechanics, Stuttgart. v. 3-B, pp. 1-9. Gringarten, A. C. 1982. Flow-test evaluation of fractured reservoirs. Geological Society of America Special Paper 189. pp. 237-263. Jenkins, D. N. and J. K. Prentice. 1982. Theory for aquifer test analysis in fractured rocks under linear (nonradial) flow conditions. Ground Water. v. 20, no. 1, pp. 12-21. Jones, J. W., E. S. Simpson, S. 1~ Neuman, and W. S. Keys. 1985. Field and Theoretical Investigation of Fractured Crystalline Rock Near Oracle, Arizona. U.S. Nuclear Regulatory Commission, Washington, DC. NRC FIN B5753. Karasaki, K. 1986. Well test analysis in fractured media. Univ. of California, Berkeley. Ph.D. dissertation. Kruseman, G. P. and N. A. de Ridder. 1991. Analysis and Evaluation of Pumping Test Data. International Institute for Land Reda- marion and Improvement, Wageningen, The Netherlands. Long, J.C.S., J. S. Remer, S. R. Wilson, and P. A. Witherspoon. 1982. Porous medial equivalents for networks of discontinuous frac- tures. Water Resources Research. v. 18, no. 3, pp. 645-658. Moench, A. F. 1984. Double porosity models for a fissured ground. water reservoir with fracture skin. Water Resources Research. v. 20, no. 7, pp. 831-846. Pankow, J. F., R. L. Johnson, J. P. Hewetson, and J. A. Cherry. 1986. An evaluation of contaminant migration patterns at two waste disposal sites on fractured porous media in terms of equivalent porous medium (EPM) model. Journal of Contaminant Hydrology. v. i, pp. 65-76. Schmelling, S. G. and R. R. Ross. 1989. Contaminant Transport in Fractured Media: Models for Decision Makers. EPA Superfund Issue Paper. EPA/540/4-89/004. Streltsova, T. D. 1988. Well Testing in Heterogeneous Formations. John Wiley and Sons, Inc., New York. Walton, W. C. 1991. Principles of Groundwater Engineering. Lewis Publishers, Chelsea, MI. Draft Comments in Response to ADNR, ADEC, and Terrasat reviews ADNR memo to Gary Prokoseh, July 30, 1997 DRAFT Responses to comments: The sand and gravel well was test pumped because DHHS was more concerned with well impacts fi.om that area of the subdivision. We tried to drill and test pump the area that was most likely to cause problems. It was unexpected to encounter a sand and gravel aquifer at that location. It is of limited areal extent, and is not present where other wells tap bedrock. The bedrock well is located more than 500 feet from wells in Scimitar that people are concerned about. We would not expect to see any response in an aquifer test of a few days duration. See subsequent comments on the feasibility of aquifer testing. ADEC letter to DHI Consulting Engineers, August 5, 1997 Responses to general comments: None Responses to specific comments: Analysis of Nitrates in Well Water 1. No comment. 2. No comment 3. The conclusion that the data do not demonstrate the presence of a clear increasing or decreasing nitrate trend does not suggest that the data are insufficient to draw sound conclusions. With the data collected to data, if a strong area-wide trend was present, the data should show it. The absence of an clear trend is a sound conclusion. Any trend that is present therefore must be weak or variable fi.om place to place or both. 4. A pattern has been identified. The pattern is that nitrate trends are weak or spatially variable or both. The conclusion of the work is that this pattern should be expected to continue with the proposed subdivision. Comments 3 and 4 seem to imply that the there is a strong trend of increasing nitrates throughout the neighborhood, we just haven't found it with our limited data. In contrast, the data show that we have been looking, but that it does not seem to be there as surmised. Aquifer Test Results and Hydrogeologic Review. No Comment. The aquifer test results can be used to project long term aquifer yield, at least in a general sense. The test data allow calculation of a specific yield for the pumped well of 4.1 gallons per minute/foot of drawdown. The pumped well has approximately 28 feet of available drawdown fi.om static conditions. A simple calculation using these values not considering DRAFt aquifer boundaries would provide a possible well yield of 115 gpm. A similar calculation using the Theis method yields an estimated drawdown of 25 ft after pumping for 100 days at a rate of 50 gpm assuming an effective well radius of 1 foot and an aquifer storativity of 0.0001. This calculation assumes no aquifer boundaries and no recharge. These calculations are more than an order of magnitude higher than the sustainable rate of 3.8 gpm projected in our report. This large difference is the reason why the long-term yield estimate is reasonable to make considering the geologic uncertainties at the site. Terrasat reviewed the field data and our conclusions and concluded that the aquifer "is capable of sustaining a long-term pumping rate of up to several gallons per minute." This provides support that the estimate is reasonable. I would be pleased to provide copies of the data to ADEC should ADEC wish to prepare an independent estimate of long-term aquifer productivity. 3. We looked for wells as suggested and found none. 4. It is not clear how "the nitrate analysis" supports the statement. "Significant" in this instance means that typical aquifer tests are too short term for defining the degree of hydraulic separation between the two aquifers. 5. The determination of "unduly affected", as stated, is established by statute, regulation, and practice under the authority of DNR. Other entities may rely on other means of addressing water availability conflicts, however, I am not aware of any other regulatory framework in Alaska that addresses these complex issues. Entities that use other means to address water availability conflicts may contradict established DNR procedures and create greater entanglements. It is not clear why ADEC is reporting on discussions regarding the phrase "unduly affected" and defining the basis for decision-making. Does ADEC have regulatory procedures in this area? 6. We disagree with this comment, and believe that the information presented in the two reports is sufficient to support the findings that have been presented. The proposed development has not been shown to have a significant adverse effect on area groundwater supplies. The proposed lot sizes and development plans compared to surrounding lots results in reasonable protection for groundwater in the area. We also believe that a substantial amount of hydrologic work has been accomplished that supports proceeding with the development and that sound, responsible, and reasonable decisions that adequately address the interests of all parties involved can be made with existing information. However, in order to address the concerns presented, we have undertaken additional hydrologic work to further substantiate that this subdivision merits approval. These findings are presented below. TERRASAT, INC, Letter to Margaret O'Brien, August 1, 1997 Comment 1. (p. 1) Anecdotal data from citizens is not presented in this report and has not been made part of the public record. The findings of this study cannot be substantiated without access to those records. 2. (p.2, paragraph 2) It is not clear how stable trends in some of the 17 of 22 wells with multiple nitrate data lead to the conclusion that nitrates are potential concern for nearly 80 percent of DRAFT area well owners. Stable trends should indicate that levels of concern should be low. Nevertheless, most residents with concerns should be more concerned with developments on or near their lot than with development in some cases over 1000 feet away. (p. 3-top p. 4) Recent work in Ontario indicates that nitrates are the contaminant of concern in areas where septic systems are used. The comparison is fair because the source of the nitrates is not as important as the perspective of how levels of nitrates in Alaska compare to other parts of North America. This allows us to scale management responses in Alaska with management responses taken elsewhere. (p. 3) The conclusion that "the sand/gravel aquifer tapped by the test well is capable of sustaining a long-term pumping rote of up to several gallons per minute" supports the Bristol conclusion that the aquifer should be capable of sustaining long-term pumping of 3.8 gpm. (p. 3) The statement that "we have found no evidence to support a conclusion that new wells in the bedrock aquifer within the proposed subdivision are capable of producing adequate water" is not supportable. · A 500 foot deep flowing artesian well tapping the bedrock aquifer was drilled on the subject property in May of 1997, with a reported yield of 360 gallons per hour. This well has subsequently been flow tested at 0.5 gpm with only 34 inches of drawdown. Projection of potential aquifer yield at this well site suggests that 360 gallons per hour (6 gpm) is conservative. · The table of data in the Terrasat report shows wells on approximately 90 properties that completely surround the subject property that have functioning wells. Of 31 reported flow tests on these properties, only 3 show yields of less than 0.5 gpm. The average flow test rate is 1.93 gpm. The average age of wells drilled on these properties is 13.8 years. The existence of this large number of wells that have successfully pumped water for many years immediately adjacent to and surrounding the proposed subdivision is strong evidence that the bedrock aquifer within the proposed subdivision is capable of producing adequate water. 6. (p. 3) The statements about decreasing well yields and increasing nitrate levels over the past several years is unsubstantiated without review of the anecdotal information. We examined publicly available nitrate analyses and summarized the results previously. Are there additional nitrate analyses available? Is this statement based on resident's review of the same data set that we reviewed with different "anecdotal" conclusions presented that are repeated but not substantiated here? 7. The conclusion that 80% of current residents do not get "the quantity or quality of water currently needed by the community" is unsupported and inaccurate. It is further stated "that there is currently a water shortage on this part of the hillside". The physical data included in the table of this report argues otherwise. Only 10 percent of lots show the presence of more than one well on the lot. Only 10 percent of wells that have been tested show less than 0.5 gpm. In comparing 31 Flow Test Yields with their Initial Yields, 14 show a decrease in yield, 10 show an increase in yield, and two show no change. Five flow tests had no reported initial yields. The number of wells showing no change or an increase in flow rate since the well were drilled is almost the same as the number showing a decrease. We have conducted a further analysis of this problem which is presented below. 8. (p. 3) The recommendations for additional aquifer testing are not practical or reasonable. Attached is a recent journal article by Gernand and Heidtman (G&H) describing an aquifer DRAFT test in a similar geologic environment. The findings of this study show that aquifer tests in low yield bedrock aquifers: · are rare · are difficult to test, analyze, and characterize (G&H tested their well for 21 days with numerous dataloggers on 13 observation wells) · are recommended to be done in conjunction with a detailed structural analysis of the bedrock · require careful evaluation of the goals of the test prior to planning the test. Wells tapping the aquifer of G&H had higher average yields that in the area of Denali View, yet a radius of influence of only 300 feet was needed to define the drawdown response almost completely. Even a 500 foot radius from the bedrock well drilled at Denali View Subdivision would not reach any wells west of Denali View in Scimitar Subdivision. We observed approximately 60 feet of water level rise in a domestic well used as an observation well during the May aquifer test. This indicates that some wells are not well connected to bedrock fractures that supply water to other wells. In order to conduct a controlled aquifer test, it would be important to take all pumping wells out of service within 1000 ft of the pumped well for at least a week to allow water levels to equilibrate. Dataloggers would need to be installed in each monitoring well. The goals of the bedrock aquifer test proposed by Terrasat are not clear. How will the degree of hydraulic connection between the upper and lower aquifers be used to help resolve the issues of (potential) decreasing long-term water production and (potential) increasing nitrate levels? The test program as outlined is likely to result in ambiguous hydraulic relationships and uncertain long-term projects for both issues, and is likely to result in a prolonged and unproductive process of data collection, analysis, review, and rebuttal; it is not likely to add any material clarity to the issues under discussion. (p. 4) We do not believe that it is appropriate to suggest that existing levels of nitrates may be a significant threat to public health. Lots adjacent to the proposed subdivision have uniformly low reported nitrate concentrations. Because trends of elevated nit'rates are weak and scattered, further studies are unlikely to discover an immediate or serious health risk. Further studies would not add material clarity to the nitrates issues. The existing quantity of data and the analysis of data are sufficient and adequate for reasonable people to recommend approval of this subdivision. So what is the real story here? There is no Peters Creek Hillside aquifer depletion going on. · If aquifer was depleted why would a newly drilled well be flowing? This does not make any sense. DRAFT · Water shortages are explainable by low well yields when first drilled and gradual sealing of aquifer fractures at the well bore over time · The solution is to rehabilitate well bores by hydrofracing · Experience in Skyline Drive area of Eagle River: 100 wells; 16 hydrofrac jobs; hard data shows all successful; lots of happy homeowners; no known failures; yield improvements up to 10x, water level rises up to 191 ft. Aquifer depletions are characterized by depressed potentiometric surfaces. The only known ADNR-imposed ban on drilling in Alaska because of a water shortage was at Auke Bay near Juneau where the potentiometfic surface of the aquifer was depressed below sea level and salt water was entering pumped wells. The flowing well proves that is not the case here. Terrasat's table shows no data regarding hydrofracing. Let's suppose that each and every well that currently has a yield problem has not been hydrofraced. It is reasonable to conclude that 10 to 20 percent of all wells tapping a low yield bedrock aquifer of this type will need hydrofracing at some point of their useful life. So what's the big deal? Community Planning seems to think that there is a certain carrying capacity of the aquifer and that we may have already exceeded it. DATA ARE LACKING TO SUPPORT THIS OPINION AND EXISTING DATA INDICATE OTHERWISE. Review of Anecdotal Data The hard data contained the Terrasat report shows that 90 percent of wells have plenty of water. This directly contradicts claims by residents about the nature of the problem. These data were criticized at the August 14 meeting at Community Planning as being out of date. At the July 19°~ community meeting, Jim Cross recommended that residents have flow tests done by an engineer to document their contentions. This recommendation was ignored. The Terrasat report included no recent test data. Instead, we are left to review anecdotal data. We are aware of anecdotal data where people's water problems are traced to pump problems or inadequate storage in the home. Of the three systems tested during 1996 and listed in the Terrasat report, all passed health authority approvals. Of the thirty reported pieces of anecdotal data ....(Let's take a look at it)... Some would Iikely pass a health authority approval Some cannot be independently determined to indicate that there is any unusual problem The rest would likely be nicely solved by hydrofracing. Hydrofracing should be regarded as a routine O &M operation for some wells in this geologic setting. Just like septic drainfields sometimes require replacing after about 15 years, some wells may need hydrofracing every 15 or 20 years. Hydrofracing is less expensive than drainfield replacement. It is a proven successful method for tapping a low-yield bedrock aquifer for long- term successful delivery ora safe and adequate amount of water to each and every homeowner. 5 WHAT NEEDS TO HAPPEN NEXT? Find out what DNR thinks is needed to address issues Find out what DEC thinks is needed to address issues Find out what DHHS thinks is needed to address issues Approach Community Planning with points of agreement. DRAFT MUNICIPALITY OF ANCHORAGE MEMORANDUM Department of Health and Human Services DATE: TO: FROM: CONCUR: SUBJECT: July 25, 1997 Zoning and Platting, CPD James Cross, PE, Program Manager, On-Site Water Quality Bruce Chandler, MD, MPH, Medical Officer S-10054, Denali View Subdivision As a follow up to the comments made in my April 18, 1997 memo regarding this subdivision, I have the following additional comments: 1. Items 2 and 3 regarding soils testing and disposal system sites have been complied with. 2. An hydrologist's study was conducted as requested. The following is a discussion of the results of this study. Title 21, section 21.15.110.B.4.b covers the requirements for sub-dividers concerning the substantiation of a safe and adequate supply of water. This section reads, in part: "The sub- divider shall submit supporting written information including: all plans, data, tests and engineering reports required by the Department of Health and Human Services to substantiate the availability of a safe and adequate volume of water for domestic purposes ..." The hydrologist's study met the requirements stipulated by DHHS in that it included the installation of two wells within the proposed subdivision, and the study monitored the affects of pumping one of these wells on the other well within the proposed subdivision and two existing domestic water supply wells serving single family homes adjacent to the proposed subdivision. The pumped well produced approximately 5.5 gallons per minute for a period of twenty four hours, during which time the water level in the second well within the proposed subdivision fluctuated, but these fluctuations did not correlate with the pumping. The two existing domestic wells which were monitored during the pump test both recovered (water levels rose within the well casings) during the 24 period of pumping. This presumably could have been caused by the cessation of water usage by the homes they support, but also shows little or no affect from the pumping. There is a possibility that these wells would have recovered faster if the pumping had not occurred, but that is unknown. More details of the study can be obtained from the report prepared by Bristol Environmental Services Corporation. These results, taken on their own, satisfy the requirements outlined above for the availability of adequate water to support the proposed subdivision. The question ofwhether the taking of this water will unduly effect existing wells nearby is discussed below. The area of the proposed Denali View Subdivision and Scimitar Subdivision to its north are underlain by bedrock. Existing wells in Scimitar Subdivision all obtain water from areas within this bedrock. Bedrock wells typically produce water from fractures and fissures within the bedrock which have relatively small flows. There are numerous fractures and fissures under these subdivisions, and they are typically not interconnected. This can be seen by comparing static water levels in various neighboring wells, which can fluctuate by over 100 feet. It also can be verified by the fact that the production of water from one bedrock well will not affect the production of water in neighboring wells. However, there is the possibility that the drilling of a new well could intersect the same fissure that an existing well is using for its production. In this case, the existing well's production would be affected (and the affected owner would presumably have water rights for protection). In my professional opinion, the chance that the drilling of the 11 wells which will serve the proposed Denali View Subdivision will affect the production of any existing well within Scimitar subdivision is slight. The chance that these 11 wells will cumulatively effect all of the wells in Scimitar Subdivision is remote. Residents of Scimitar Subdivision have stated that their wells have produced less water in recent years. Due to the fact that there has been little or no development in this subdivision in the 90's, this drop in production is most likely caused by climatic effects (lower rainfall and snowfall to recharge groundwater sources), as is the case within ether areas of the Municipality of Anchorage. Because ingestion of excessive amounts of nitrate can cause adverse health effects in very young infants and susceptible adults, the United States Environmental Protection Agency (EPA) has established a maximum acceptable level, known as the Maximum Contaminant Level (MCL), for nitrate in public drinking water supplies. This level is 10 milligrams per liter (mg/I)-- often expressed as 10 parts per million (PPM)--measured on the basis of the nitrogen content of nitrate. This standard of 10 PPM nitrate-nitrogen was set to prevent the occurrence of infant methemoglobinemia with a reasonable margin of safety. Consumption of water with less than 10 mg/I nitrate nitrogen poses no identified health risk for humans of any age. Some neighboring homeowners have voiced concern about the potential degradation of water quality, especially in regard to nitrate concentrations, on existing wells in the vicinity of the Denali View subdivision. While most properties in Scimitar Subdivision have Iow nitrate levels, some properties have moderate levels below the EPA MCL; two properties have levels which exceed the EPA MCL. These elevations appear to be isolated and localized. There is no evidence of widespread nitrate elevation throughout the subdivision or underlying aquifer. Further study would be required to determine the source of elevated nitrates in each well. Nitrate levels in water from two test wells in the Denali View Subdivision have been very Iow or non-detectable. Based on available data, it is unlikely that responsible development of Denali View subdivision will significantly impact the drinking water nitrate levels of neighboring properties. Details of the nitrate concentrations and their distribution can be seen in the report prepared by Bristol Environmental Services. The development of Denali View Subdivision will be monitored by the DHHS, and nitrate levels will be followed through the Health Authority Approval which includes the testing of wells. If there is any indication of elevated nitrate levels within, or due to development in Denali View, DHHS will require the installation of nitrate reducing septic systems for any newly developed lots. To accomplish this, the following plat note shall be added: "Nitrate reducing septic systems may be required by DHHS for the development of each lot within this subdivision." I am also aware that a second hydrologist's report is being prepared by a different firm at the request of some homeowners surrounding this proposed subdivision. I have seen no information from this report as of this date. ML.N'ICIPALITY OF ANCHORAGE MEMORANDUM Department of Healrh and Human Sen'ices DATE: July 25. 1997 TO: Zonin~ and Platting, CPD /q' "~ (~l~e; Cross. PE, Program Manager, On-Site VVater Quality FROM: CONCUR: Bruce Chandler, MD, MPH, Medical Officer SUBJECT: S-10054. Denali View Subdivision RECEIVED ;UL :' q ~9S7' As a follow up to the comments made in my April 18, 1997 memo regarding this subdivision, have the following additional comments: 1. Items 2 and 3 regarding soils testing and disposal system sites have been complied with. 2. An hydrologist's study was conducted as requested. The following is a discussion of the results of this stucy. Title 21, section 21.15.110.B.4.b covers the requirements for sub-dividers concerning the substantiation of a safe and adequate supply of water. This section reads, in part: "The sub- divider shall submit supporting wdtten information including: all plans, data, tests and engineering reports required by the Department of Health and Human Services to substantiate the availability of a safe and adequate volume of water for domestic purposes ..." The hydrologist's study met the requirements stipulated by DHHS in that it included the installation of two wel!s within the proposed subdivision, and the study monitored the affects of pumping one of these wells on the other well within the proposed subdivision and two existing domestic water supply wells serving single family homes adjacent to the proposed subdivision. The pumped well produced approximately 5.5 gallons per minute for a period of twenty four hours, during which time the water level in the second well within the proposed subdivision fluctuated, but these fluctuations did not correlate with the pumping. The two existing domestic wells which were monitored during the pump test both recovered (water levels rose within the well casings) during the 24 period of pumping. This presumably could have been caused by the cessation of water usage by the homes they support, but also shows little or no affect from the pumping. There is a possibility that these wells would have recovered faster if the pumping had not occurred, but that is unknown. More details of the study can be obtained from the report prepared by Bdstol Environmental Services Corporation. These results, taken on their own, satisfy the requirements outlined above for the availability of adequate water to support the proposed subdivision. The question of whether the taking of this water will unduly effect existing wells nearby is discussed below. The area of the proposed Denali View Subdivision and Scimitar Subdivision to its north are underlain by bedrock. Exisdng wells in Scimitar Subdivision all obtain water from areas within this bedrock. Bedrock wells typically produce water from fractures and fissures within the bedrock which have relatively small flows. There are numerous fractures and fissures under these subdivisions, and they are typically not interconnected. This can be seen by comparing static water levels in vadous neighboring welIs, which can fluctuate by over 100 feet. It also 23-3 ! ! I I I t I i I I can be verified by the fact that the sroduction of water from one bedrock well will not affect the production of water in neighborinc ,ivetls. However, there is the possibility that the ddfling of a new well could intersect the same fissure that an existing well is using for its product on. In this case, the existing well's production would be affected (and the affected owner would presumably have water dghts for protection). In my professional opinion, the chance that the drilling of the 11 wetls which will serve the proposed Denali View Subdivision will affect the production of any existing well within Scimitar subdivision is slight. The chance that these 11 wells will cumulatively effect all of the wells in Scimitar Subdivision is remote. Residents of Scimitar Subdivision have stated that their wells have produced less water in recent years. Due to the fact that there has been little or no development in this subdivision in he 90 s, this drop in production is most likely caused by climatic effects (lower rainfall and snowfall to recharge groundwater sources), as is the case within other areas of the Municipality of Anchorage. Because ingestion of excessive amounts of nitrate can cause adverse health effects in very young infants and susceptible adults, the United States Environmental Protection Agency (EPA) has established a maximum acceptable level, known as the Maximum Contaminant Level (MCL), for nitrate in public ddnking water supplies. This level is 10 milligrams per liter (mg/I)-often expressed as 10 parts per million (PPM)-measured on the basis of the ni~ogen content of nitrate. This standard of 10 PPM nitrate-nitrogen was set to prevent the occurrence of infant methemoglobinemia with a reasonable margin of safety. Consumption of water with less than 10 mg/l nitrate nitrogen poses no identified health risk for humans of any age. Some neighboring homeowners have voiced concern about the potential degradation of water quality, especially in regard to nitrate concentrations, on existing wells in the vicinity of the Denali View subdivision. While most properties in Scimitar Subdivision have Iow nitrate levels, some properties have moderate levels below the EPA MCL; two properties have levels which exceed the EPA MCL. These elevations appear to be isolated and localized. There is no evidence of widespread nitrate elevation throughout the subdivision or underlying aquifer. Further study would be required to determine the source of elevated nitrates in each well. Nitrate levels in water from two test wells in the Denali View Subdivision have been very Iow or nan-detectable. Based on available data, it is unlikely that responsible development of Denali View subdivision will significantly impact the drinking water nitrate revels of neighboring properties, Details of the nitrate concentrations and their distribution can be seen in the report prepared by Bdstol Environmental Services. The development of Denali View Subdivision will be monitored by the DHHS, and nitrate levels will be followed through the Health Authority Approval which includes the testing of wells, if there is any indication of elevated nitrate levels within, or due to development in Denali View, DHHS will require the installation of nitrate reducing'septic systems for any newly developed lots. To accomplish this, the following plat note shall be added: "Nitrate reducing septic systems.,may b,e required by DHHS for the development of each lot within this subdivision." MUNICIPALITY OF ANCHORAGE MEMORANDUM Department of Health and Human Services DATE: TO: FROM: CONCUR: SUBJECT: July 25, 1997 Zoning and Platting, CPD James Cross, PE, Program Manager, On-Site Water Quality Bruce Chandler, MD, MPH, Medical Officer S-10054, Denali View Subdivision As a follow up to the comments made in my April 18, 1997 memo regarding this subdivision, I have the following additional comments: 1. Items 2 and 3 regarding soils testing and disposal system sites have been complied with. 2. An hydrologist's study was conducted as requested. The following is a discussion of the results of this study. Title 21, section 21.15.110.B.4.b covers the requirements for sub-dividers concerning the substantiation of a safe and adequate supply of water. This section reads, in part: "The sub- divider shall submit supporting written information including: all plans, data, tests and engineering reports required by the Department of Health and Human Services to substantiate the availability of a safe and adequate volume of water for domestic purposes ... The hydrologist's study met the requirements stipulated by DHHS in that il included the installation of two wells within the proposed subdivision, and the study monitored the affects of pumping one of these wells on the other well within the proposed subdivision and two existing domestic water supply wells serving single family homes adjacent to the proposed subdivision. The pumped well produced approximately 5.5 gallons per minute for a period of twenty four hours, during which time the water level in the second well within the proposed subdivision fluctuated, but these fluctuations did not correlate with the pumping. The two existing domestic wells which were monitored during the pump test both recovered (water levels rose within the well casings) during the 24 period of pumping. This presumably could have been caused by the cessation of water usage by the homes they support, but also shows little or no affect from the pumping. There is a possibility that these wells would have recovered faster if the pumping had not occurred, but that is unknown. More details of the study can be obtained from the report prepared by Bristol Environmental Services Corporation. These results, taken on their own, satisfy the requirements outlined above for the availability of adequate water to support the proposed subdivision. The question of whether the taking of this water will unduly effect existing wells nearby is discussed below. The area of the proposed Denali View Subdivision and Scimitar Subdivision to its north are underlain by bedrock. Existing wells in Scimitar Subdivision all obtain water from areas within this bedrock. Bedrock wells typically produce water from fractures and fissures within the bedrock which have relatively small flows. There are numerous fractures and fissures under these subdivisions, and they are typically not interconnected. This can be seen by comparing static water levels in various neighboring wells, which can fluctuate by over 100 feet. It also can be verified by the fact that the production of water from one bedrock well will not affect the production of water in neighboring wells. However, there is the possiu~lity that the drilling of a new well could ihLersect the same fissure that an existing well is using for its production. In this case, the existing well's production would be affected (and the affected owner would presumably have water rights for protection). In my professional opinion, the chance that the drilling of the 11 wells which will serve the proposed Denali View Subdivision will affect the production of any existing well within Scimitar subdivision is slight. The chance that these 11 wells will cumulatively effect all of the wells in Scimitar Subdivision is remote. Residents of Scimitar Subdivision have stated that their wells have produced less water in recent years. Due to the fact that there has been little or no development in this subdivision in the 90's, this drop in production is most likely caused by climatic effects (lower rainfall and snowfall to recharge groundwater sources), as is the case within other areas of the Municipality of Anchorage. Because ingestion of excessive amounts of nitrate can cause adverse health effects in very young infants and susceptible adults, the United States Environmental Protection Agency (EPA) has established a maximum acceptable level, known as the Maximum Contaminant Level (MCL), for nitrate in public drinking water supplies. This level is 10 milligrams per liter (mg/I)-- often expressed as 10 parts per million (PPM)--measured on the basis of the nitrogen content of nitrate. This standard of 10 PPM nitrate-nitrogen was set to prevent the occurrence of infant methemoglobinemia with a reasonable margin of safety. Consumption of water with less than 10 mg/I nitrate nitrogen poses no identified health risk for humans of any age. Some neighboring homeowners have voiced concern about the potential degradation of water quality, especially in regard to nitrate concentrations, on existing wells in the vicinity of the Denali View subdivision. While most properties in Scimitar Subdivision have Iow nitrate levels, some properties have moderate levels below the EPA MCL; two properties have levels which exceed the EPA MCL. These elevations appear to be isolated and localized. There is no evidence of widespread nitrate elevation throughout the subdivision or underlying aquifer. Further study would be required to determine the source of elevated nitrates in each well. Nitrate levels in water from two test wells in the Denali View Subdivision have been very Iow or non-detectable. Based on available data, it is unlikely that responsible development of Denali View subdivision will significantly impact the drinking water nitrate levels of neighboring properties. Details of the nitrate concentrations and their distribution can be seen in the report prepared by Bristol Environmental Services. The development of Denali View Subdivision will be monitored by the DHHS, and nitrate levels will be followed through the Health Authority Approval which includes the testing of wells. If there is any indication of elevated nitrate levels within, or due to development in Dena~i View, DHHS wilt require the installation of nitrate reducing septic systems for any newly developed lots. To accomplish this, the following plat note shall be added: "Nitrate reducing septic systems may be required by DHHS for the development of each lot within this subdivision." I am also aware that a second hydrologist's report is being prepared by a different firm at the request of some homeowners surrounding this proposed subdivision. I have seen no information from this report as of this date. AL 'ICiPALITY OF ANCFt, rl.4GE .~IEMORAND UM Department of Health and Human Sen'ices CATE: July 25. 1997 TO: Zonino and F!atting, CPD /1...-,(...]~.~l~el Cross. PE, Program Manager, On-Site Water Quaiity FROM: CONCUR: Bruce Chandler, MD, MPH, Medical Off~cer SUBJECT: S-100.~4. Denaii View Subdivision RECEIVED As a follow up to the comments made in my April 18, 1997 memo re]arding this subdivision, have the following additional comments: 1. Items 2 and 3 regarding soils testing and disposal system sites have been complied with. 2. An hydrdogist's study was conducted as requested. The following is a discussion of the results of this study. Title 21, section 21.15.110.B.4.b covers the requirements for sub-dividers concerning the substantiation of a safe and adequate supply of water. This section reads, in part: "The sub- divider shall submit supporting written information including: all plans, data, tests and engineering reports required by the Department of Health and Human Services to substantiate the availability of a safe and adequate volume of water for domestic purposes ...* The hydrologist's study met the requirements stipdated by DHHS in that it included the installation of two we!!s within the proposed subdivision, and the study monitored the affects of pumping one of these wells an the other well within the proposed subdivision and tvvo existing domestic water supply wells serving single family homes adjacent to the proposed subdivision. The pumped well produced approximately 5.5 gallo0s per minute for a period of twenty four hours, dudng which time the water level in the second well within the proposed subdivision fluctuated, but these fluctuations did not correlate with the pumping. The two existing domestic wells which were monitored during the pump test both recovered (water levels rose within the well casings) during the 24 period of pumping. This presumably could have been caused by the cessation of water usage by the homes they support; but also shows liffie or no affect from the pumping. There is a possibility that these wells would have recovered faster if the pumping had not occurred, but that is unknown. More details of the study c~n be obtained from the report prepared by Bristol Environmental Services Corporation. These results, taken on their own, satis,'~/the requirements outlined above for the availability of adequate water to support the proposed ~ubdivision. The question of whether the taking of this water will unduly effect existing wells nearby is discussed below. The area of the proposed Oenali View Subdivision and Scimitar Subdivision to its north are underlain by bedrock. ~sting wells in Scimitar Subdivision ali obtain water from areas within this bedrock. Bedrock wells tTpically produce water from fractures and fissures within the bedrock which have relatively small flows. There are numerous fractures and fissures under these subdivisions, and they are typically not interconnected. This can be seen by comparing static water leve!s in vsdous neighboring wells, which can fluctuate by over 100 feet. It also 23-3 can be verified by the i'act that the production cf water from one bedrock well wiil not affect the production of water in neighboring ',';ells. Ho',vever, there is the possibility that the drilling of a new well could intersect the same fissure that an existing well is using for its production. In this Case, the existing well's production would be affected (and the affectea owner wouid presumably have water dghts for protection). In my professional opinion, the chance that the drilling of the 11 wells which will serve the proposed Denali View Subdivision will affect the production of any existing well within Scimitar subdivision is slight. The chance :hat these 11 wells will cumulatively effect ell o~' the wells in Scimitar Subdivision is remote. Residents of Scimitar Subdivision have stated that their wells have produced less water in recent years. Due to the fact that t~here has been little or no development in this subdivision in the 90's, this drop in production is most likely caused by climadc effects (lower rainfall and snowfall to recharge groundwater sources), as is the case within other areas of the Municipality of Anchorage. Because ingestion of excessive amounts of nitrate can cause adverse health effects in very young infants and susceptible adults, the United Slates Environmental Protec+Jon Agency (EPA) has established a m~ximum acceotable level, known as the M~ximum Contaminant Level (MCL), for nit. rat=' ' - ~n public d,dnking water supplies. This level is 10 milligrams per liter (mg/l)-O~en expressed as 10 parts per million (PPM)-measured on the basis of the nitrogen content of nitrate. This standard of 10 PPM nitr~te-nitrogen was set to prevent the occurrence n,~nt methemogJob nemco with a reaaonab e margin of safety. Consumption of water with less than 10 mg/I nitrate nitrogen poses no identified health dsk for humans of any age. Some neighboring homeowners have voiced concern about the potential degradation of water quality, especially in regard to nitrate concentrations, on existing wells in the vicinity of the Denali View subdivision. While most properties in Scimitar Subdivision have Iow nitrate levels, some properLies have moderate lave s below the EPA MCL; two proper'des have levels which exceed the EPA MCL These elevations appear to be isolated and loCalized. Thera is no evidence, of widespread nitrate elevation throu<:hout the subdivision or u Further ,,ud, would be requ,red to determine the source of elevated n,tr:tde:diYn'nega:hq,~ Nitrate levels in water from two test wells in the Denali View Subdivision have been very Iow or non-detectable. Based on available data, it is unlikely that responsible development of Denali View subdivision will significantJy impact the drinking water nitrate levels of neighboring properties. Details of the nitrate c=ncentrations and their distribution Can be seen in the report prepared b · . y Bns,o Enwronmental Services. The development of Denali View Subdivision will be monitored by the DHHS, and nitra~te leve!s will be followed [hrouc~h the Health Au*~,-,,~.~. - ' .... ,~y Approval which includes the testino cf wells. If :[here is any indication of elevated nitrate levels within, or due to development ir'7 Denali View, DHHS will require the inst- ' -, - ' . ¢llat~on of n~tr~e reducing septic systems for any newly developed lots. To accomplish this, the following plat note shall be added: "Nitrate reducing septic systems .,may be required by DHHS for the development of each lot within this subdivision." MUNICIPALITY OF ANCHORAGE MEMORANDUM Department of Health and Human Services DATE: TO: FROM: CONCUR: SUBJECT: July 25, 1997 Zoning and Platting, CPD James Cross, PE, Program Manager, On-Site Water Quality Bruce Chandler, MD, MPH, Medical Officer S-10054, Denali View Subdivision As a follow up to the comments made in my April 18, 1997 memo regarding this subdivision, have the following additional comments: 1. Items 2 and 3 regarding soils testing and disposal system sites have been complied with. 2. An hydrologist's study was conducted as requested. The following is a discussion of the results of this study. Title 21, section 21.15.110.B.4.b covers the requirements for sub-dividers concerning the substantiation of a safe and adequate supply of water. This section reads, in part: "The sub- divider shall submit supporting written information including: all plans, data, tests and engineering reports required by the Department of Health and Human Services to substantiate the availability of a safe and adequate volume of water for domestic purposes ..." The hydrologist's study met the requirements stipulated by DHHS in that it included the installation of two wells within the proposed subdivision, and the study monitored the affects of pumping one of these wells on the other well within the proposed subdivision and two existing domestic water supply wells serving single family homes adjacent to the proposed subdivision. The pumped well produced approximately 5.5 gallons per minute for a period of twenty four hours, during which time the water level in the second well within the proposed subdivision fluctuated, but these fluctuations did not correlate with the pumping. The two existing domestic wells which were monitored during the pump test both recovered (water levels rose within the well casings) during the 24 period of pumping. This presumably could have been caused by the cessation of water usage by the homes they support, but also shows little or no affect from the pumping. There is a possibility that these wells would have recovered faster if the pumping had not occurred, but that is unknown. More details of the study can be obtained from the report prepared by Bristol Environmental Services Corporation. These results, taken on their own, satisfy the requirements outlined above for the availability of adequate water to support the proposed subdivision. The question of whether the taking of this water will unduly effect existing wells nearby is discussed below. The area of the proposed Denali View Subdivision and Scimitar Subdivision to its north are underlain by bedrock. Existing wells in Scimitar Subdivision all obtain water from areas within this bedrock. Bedrock wells typically produce water from fractures and fissures within the bedrock which have relatively small flows. There are numerous fractures and fissures under these subdivisions, and they are typically not interconnected. This can be seen by comparing static water levels in various neighboring wells, which can fluctuate by over 100 feet. It also can be verified by the fact that the production of water from one bedrock well will not affect the production of water in neighboring wells. However, there is the pOSS~L~,,~ty that the drilling of a new well could ~, ,.~rsect the same fissure that an existing well is using for its production. In this case, the existing well's production would be affected (and the affected owner would presumably have water rights for protection). In my professional opinion, the chance that the drilling of the 11 wells which will serve the proposed Denali View Subdivision will affect the production of any existing well within Scimitar subdivision is slight. The chance that these 1 't wells will cumulatively effect all of the wells in Scimitar Subdivision is remote. Residents of Scimitar Subdivision have stated that their wells have produced less water in recent years. Due to the fact that there has been little or no development in this subdivision in the 90's, this drop in production is most likely caused by climatic effects (lower rainfall and snowfall to recharge groundwater sources), as is the case within other areas of the Municipality of Anchorage. Because ingestion of excessive amounts of nitrate can cause adverse health effects in very young infants and susceptible adults, the United States Environmental Protection Agency (EPA) has established a maximum acceptable level, known as the Maximum Contaminant Level (MCL), for nitrate in public drinking water supplies. This level is 10 milligrams per liter (mg/I)-- often expressed as 10 parts per million (PPM)--measured on the basis of the nitrogen content of nitrate. This standard of 10 PPM nitrate-nitrogen was set to prevent the occurrence of infant methemoglobinemia with a reasonable margin of safety. Consumption of water with less than 10 mg/I nitrate nitrogen poses no identified health risk for humans of any age. Some neighboring homeowners have voiced concern about the potential degradation of water quality, especially in regard to nitrate concentrations, on existing wells in the vicinity of the Denali View subdivision. While most properties in Scimitar Subdivision have Iow nitrate levels, some properties have moderate levels below the EPA MCL; two properties have levels which exceed the EPA MCL. These elevations appear to be isolated and localized. There is no evidence of widespread nitrate elevation throughout the subdivision or underlying aquifer. Further study would be required to determine the source of elevated nitrates in each well. Nitrate levels in water from two test wells in the Denali View Subdivision have been very Iow or non-detectable. Based on available ~lata, it is unlikely that responsible development of Denali View subdivision will significantly impact the drinking water nitrate levels of neighboring properties. Details of the nitrate concentrations and their distribution can be seen in the report prepared by Bristol Environmental Services. The development of Denali View Subdivision will be monitored by the DHHS, and nitrate levels will be followed through the Health Authority Approval which includes the testing of wells. If there is any indication of elevated nitrate levels within, or due to development in Denali View, DHHS will require the installation of nitrate reducing septic systems for any newly developed lots. To accomplish this, the following plat note shall be added: "Nitrate reducing septic systems may be required by DHHS for the development of each lot within this subdivision." I am also aware that a second hydrologist's report is being prepared by a different firm at the request of some homeowners surrounding this proposed subdivision. I have seen no information from this report as of this date. Municipalily ol Anchorage DEPARTMENT OF HEALTH & HUMAN SERVICES 825 'L" Street Anchorage, Alaska 99502-0650 SOILS LOG -- PERCOLATION TEST PERFORMED FOR:_Paul Myers [)ATE PERFD LEGAL DESCRIPTION: Lot 1 Denali View Township, Range, Section: TH1 t 2 3 4 5 6 7 8 9 10 Organic Overburden Frozen to 1 ' Organic Silt with Sand and Roots to 3' SI. Silty Sandy Gravel Rock to 12" with Occasional Boulders to SLOPE WAS GROUND WATER ENCOUNTERED? NO IF YES, AT WHAT DEPTR? 13 - ,~,: 4 / 3 0/_9' SITE PLAN 14 Bottom 15 ~6 17 18 20 - Time Time Water Drop · 6" PERCOLATION RATE 0 5 (m,nules/,nch) PERC HOLE DIAMETER TEST RUN BETWEEN 4 o 5 FT AND __5. 0 F1 COMMENTS 80ils presoaked prior ~o ru~nq percolation test PERFORMED BY: __Dee High -- I~~~ CERIIFY THAT THIS TEST WAS PERFORMED IN 7~-008 (Dev. 4/85) TH2 PERFORMED FOR: LEGAL DESCRIPTION:_L. QL2 Dena 2. 3- 4 5 6 7 8 9 10 11 12 13 16- 17- 18- 19- 20- Vi Rw Organic Overburden Municipalil¥ of Anchorage DEPARTMENT OF HEALTH & HUMAN SERVICES SOILS LOG -- PERCOLATION TEST Paul Myers DATE Township, Range, Section: Organic Silt with Sand Roots to 3' S1. Silty Sandy Gravel Dry Rock to 12" Prevalent Occasional Boulders to SLOPE SITE PLAN WAS G~qOUND WATER ENCOUNTERED? NO 4/30/97 Bottom Oeplh I, Waler AlJ)r Monitoring? L'done' Time Time Water Drop PERCOLATION RATE 0.3 (mmules/mch) PERC HOLE DIAMETEr{ rEST RUN BEIWEEN 4. 5 FT AND 5, 0 FT COMMENTS Soils presoaked prior t~An~ Dercolation~_~t ?2 008 (Rev. 4/85; Municipality of Anchorage DEPARTMENT OF HEALTH & HUMAN SERVICES 825 "L" Street, Anchorage, Alaska 99502-0650 SOILS LOG -- PERCOLATION TEST PERFORMED FOR:_Pau1 Myers DATE PERFI TH3 LEGAL DE SCRIPTION:_~L~O 6" Organic Overburden Organic Silt wlth Sand Roots to 3' NFS Sand, Dry Gravelly Sand, Dry Occasional Rock to 8" t0 11 12 13 14 15. 16- 17- 18- 19= Bottom Township, Range, Seclion: SLOPE WAS GROUNDWATER ENCOUNTERED? NO SITE PLAN rleplh Io Waler After s L IF YES, ATWIIAT O DEPTR? PERCOLATION RATE 0.7 (m~nules/mch) PERC I-IDLE DIAMETER TESI R~WE£N --4 FT AND __4 , 5 FT COMMENTS Soils presoaked r~r ~o rufh~in9 percolation test ____ fg.. PERFORMED BY Dee Hlqh i ~ · : CERTIFY THAT '[FILS TEST WAS PERFORMED ACCORDANC~ WITFI ALL STATE AND MUNICIPAL GUIDELINESIN ErFECT O~ATE DATE: ~ /~ ' ~ 72-008 (Rev, 4/85) Municipalily ol Anchorage DEPARTMENT OF HEALTH & HUMAN SERVICES 825 "E~' S[reet, Anchorage, Alaska 99502-0650 SOILS LOG -- PERCOLATION TEST PERFORMEO FOR:_ E'au.L~~ DATE PERFORM TH4 LEGAL DESCRIPTION: 8 9 10- 11 13- 14 15 16 17 18 19 20 Organic Overburden Organic Silt with Roots Si. Silty Sandy Gravel Rock to 12" Occasional Boulder to 30" Dry Bottom Township, Range, Sect?_n_: SLOPE WAS GROUNO WATER ENCOUNTERED? NO SITE PLAN _4_/30 / 97 [Jflplfl lo Waler After Moflllering ? ~]~oIle PERCOLATION RATE 3, 7 (mmules/,nch) PERC HOLE DIAMETER TESI RUN 8E]'WEEN 4 . 5 FT AND 5 . 0 COMMENTS Soils presoaked prio~o ru~u~dnqinq percolation test Municipalily of Anchorage DEPARTMENT OF HEALTH & HUMAN SERVICES 825 "L" Slreet, Anchorage, Alaska 99502-0650 SOILS LOG -- PERCOLATION TEST PERFORMED FOR:_Pau1 Myers LEGAL DESCRIPTION; Lot 5 Denali View 10WRShip, Range, Section: TH 5 1 2 3 4 5 6 7 8 g 10- 11 13 14 15 16 17 18 19- 20- Organic Overburden Organic Silt with Sand Roots to 3' Silty Sandy Gravel Rocks to 12" Prevalent Occasional Boulders to 3' Dry SLOPE SITE PLAN Bottom WAS GDOUNO WALED ENCOUNTERED? No IF YES. AT WHAT O DEPTH? p E §eplh lo W~ler Aller : Monilotino? None Dale: __4/30/97 Beading [3ale Gross Net Depth to Net Time Time Water Drop PERCOLATION RATE 0 · 5 Im,rlules/,nchl PERC I tOLE DIAMETER TEST RUN BETWEEN _~ FTAND ~ . 5 FT COMMENTS _ S(~i lS Dre~o~tke~l_p]LLo~nninq_tlD_rcolation test PERFORMED BY: ~~ .... I . ~ ~ CER~IFY THAT THIS TEST WAS PERFORMED IN ACCORDANCE WITH ALL STAIE AND MUNICIPAL GUIDEUNES IN EFFECT ON ~DAIE DATE: ~ ~2 008 IRev. 4/85) TH6 Municipalily of Anchorage DEPARTMENT OF tlEALTH & HUMAN SERVICES 825 "L" Street, Anchorage, Alaska 99502-0650 SOILS LOG -- PERCOLATION TEST PERFORMED FOR:. P.~I! 1 LEGAL DESCRfP rlON:~LQ~ 1 2 3 4 5 6 7- 8- 9- 10~-- Small Seep 11 Bottom 12 13 14 15 16 17, 18- 19- 20- HyeLs 6 Denali View Organic Overburden Organic Silts with Sand Roots 2½' Silty Sandy Gravel Dense [)ATE PERF( lownship, Range, Se¢lion: SLOPE WAS GROUND WATER ENCOUNTERED? YeS S L DEPTII; 1 p 0ep~h ~0 Wa~e, After 4 / 3 0 / 97 Monll0rino? 6.7 ' Da~e: SITE PLAN Time 'rime Water Drop PERCOLATION RATE 3 . 5 (mmules/{nchl PERC HOLE DIAMETER 6" T[ES'-~ETWEEN 4. 5 . FT AND 5. 0. FT COMMENTS .q,'~ 1 ~ p]::~.SZ:ZaJ~eJ~ prio¥ to r~.,q.n±nq percola,t±on test DA,E: 72-008 {Rev. 4/85) Municipalily el Anchorage DEPARTMENT OF ItEAI_TH & HUMAN SERVICES 825 "L" SIreet, Anchorage, Alaska 99502-0650 SOILS LOG -- PERCOLATION TEST EALt PERFORMED FOR:~J}~ a ~_~]~V e r s LEGAl. DESCRIPTION: Lot 7 Denali DATE PERF View Township. Range, Section: TH7A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 16- 17- 18- lg 2O Organic Overburden 1.5' Organic Silt with Sand Occasional Roots to 3' Frozen t'o 3' S1. Silty Sand V Bottom SLOPE WAS GROUND WATER ENCOUNTERED? Yes s L IF YES, AT WtlAT O DEPTR? 1 2.0 ' p; E fleplhlo Water After 8 ~ Moniledng7 Date: 4 / 3 0/_9'7 SITE PLAN Time Time Water Drop PERCOLATION RAT TEST RUN BETWEEN 5 FT AND 5. 5 FT COMUENTS Soils presoaked prior to .runninq perc, olation test PERFORMED BY: Dee High ' ' ACCORDANCE WI]H ALL STA~E AND MUNICIPAL GUIDELINES ~N EFFECT O~IS 72-008 (Rev 4/85) Municipalily of Anchorage DEPARTMENT OF HEALTH & HUMAN SERVICES 825 "L" Sireel, Anchorage, Alaska 99502-0650 SOILS LOG -- PERCOLATION TEST PERFORMED FOR:_ Pall] M~(~rs LEGAL DESCRIPIION: Lot 7 Denali View DATE PERFOR ]-ownship, Range, Seclion: TH7B 2 3 4 5 6 7 8 10- 11 13- 14 15 16 17 18 19- 20- 1' Organic Overburden Organic Silt with Sand Roots to 3' NFS Sand Dry Gravelly Sand with Rock to 8" SLOPE SITE PLAN WAS GROUND WATER ENCOUNTERED? Yes IF YES. ATWHAT E Depth lo Waler Aller Monilorinfl? _ lO.4~a~e: 4/30/97 Gross Net Depth to Net Readlr~g Date Time Th'ne Water Drop PERCOLATION RATE 0. 8 (mmules/mch) PERC HOLE DIAMETER 1ES] RUN BETWEEN 5o5_FTAND 6.6 ET COMMENTS Soils presoaked prior to runninq perqolation test PEREORMED S',': Dee _}i~h ~~/~'~/'/ CERTIFY TI-IAT THIS TEST WAS PEREORMED IN ACCORDANCE WITH ALE STATE AND MUNICIPAL GUIDELINES / '"~/IN EPFECTtO~ ].,~S DATE. DATE: "'~'~//~ ~ ~ 7 72-008 (Rev 4/85) TH8 Mu.icipalily of Anchorage DEPAR'rMEN'T OF IIEALIFI & HUMAN SERVICES 825 "L' Slreet. A.cho~age, Alaska 99502-0650 SOILS LOG --. PERCOLATION TEST PERFOnMED r'~l[~ ~gul Myers LEG^L r)E.~CR,,'I,ON L_O. t_~8_ De~.n_ali__~View~ Organic Overburden I 2 3- 5 6 7 8 g 10 11 12 Organic Silt with Occasional Roots to ( E FLG ~ Er~q%5 SEAL} Township, Ra.ge, Section: ~'N-%~ ' Si. Silty Sandy Gravel Rock to 12" Occasional Boulders to Dry 13 Bottom SLOPE 3' 30' SI I E P LAN 14 15- 16- 17 18 lg 20 Time Time Wat.~ Drop M[micipalil¥ of Anchorage DEPARTMENT OF I IFAI_71i & HUMAN SERVICES 825 "L" Sheel, Anchorage, Alaska 99502-0650 SOILS LOG -- PERCOLATION TEST PERFORMED FOR. ~a~ul___M_yers DATE PERFOR~ TH9 1 2 3 4 5 6 7- 8- 9 10 ~2 13 Township, Range, Section: SLOPE Organic Overburden Frozen to 1' Organic Silt with Sand with Roots to 2' S1. Silty Sandy Gravel Rock to 6" Occasional Boulders to 24" Hit 60" Boulder Dry SITE PLAN Sl. Silty Gravelly Sand Rock to 3" No 14 15 16 17, 18- 19- 20- Bottom Net Drop COMMEN[$ _~_Qi!M .p._r_e_soaked prip_r_~p run~nq percolation test_ ~ .... ' ............ CERTIFY fltAT ~lllS TEST WAS PERFORMED IN Mlmicipalily of Anchorage DEPARTMENT OF IlEAl_TH & HUMAN SERVICES 825 "L" Street, Anchorage, Alaska 99502-0650 SOILS LOG -- PERCOLATION TEST PERFOnMED F¢iiJ p~.U__l_. Mye. r~s___ LEGAL DESCnU'JI~ Lot 10 Denali View TH10 1 2 3 4 5 6 7 8 9 10 t! 12 13 Organic Overburden Organic Silts with Roots NFS Sand Dry Clean Gravelly Sand Dry Occasional Rock to 8" SLOPE No $ 4~29/97 14 15 17 Bottom 20~ comments __SQi!s_..g~esoa_ked pr~.'~q_~_perco~at~on LO~.~ TH1 1 Municipality o! Anchorage DEPARTMENT OF tlEALTH & HUMAN SERVICES 825 "L" Street, Anchorage, Alaska 99502-0650 SOILS LOG -- PERCOLATION TEST PERFORMED LE6AL UESCmPHOr,~ ..L.o..t__l 1 ! 2 3 4 5 6 7 8 9 10 I1 12 13 Organic Organic Roots to Denali_.~i~_ Overburden Silt with Sand 3' Sandy Gravel, Rock to 12" Dry Lots of ~'.'"';'.~4~?,, Township, Range, Section; SLOPE SITE PLAN F 4/29/97 LZI t4- 17 18 19 20 Bottom Date 1ESI~Ilff,~BETWEEN 4o 5 FTAND 5.0 FI ................... ~ h ,/// MUNICIPALITY OF ANCHORAGE .Department of ~ealth and l~uman Services P.O. Box 196650 Anchorage, Alaska 99519-6650 Date: April 18, 1997 To: (~/r~Zo~ng and Platting, CPD From~mes Cross, P.E., Program Manager, On-Site/Water Quality Subjec¢ Request for Comments on Cases Due: April 18, 1997 The Environmental Services Division, On-Site Services Program, has reviewed the folloxving cases and has these comments: S-9190: Hamann. No objections. S-9920: Cedar Estates. No objections. S-10013: Gout. Same comments as my memo dated 02/06/97. S-10053: Skyway Park Estates. No objections. S-10054: Denali View. 1. A hydrologist's study and report must be conducted to determine the availability ofpotable water for this subdivision. The study shall include the installation and testing of a minimum of'two (2) wells and their effects on neighboring properties. 2. Soils testing, percolation testing and ground water monitoring to confirm the suitability for development using on-site wastewater disposal systems is inadequate. All soils logs must bear the original seal and signature of' the engineer. 3. Areas designated for the original and replacement wastewater system disposal sites (reserve areas) must be identified and must meet all criteria specified in AMC 15.65, including slope setback requirements. SEP-29-97 MO~ 20:06 RE/MA"' % EAGLE RIVER FAX NO, 9076960214 ~ Depadment ol Health and~ Human Services P.O. Box 196850 Anchorage, Alaska / June 2, 19~3 C~RTIF~ED David J. & Loretta H. PYall American Embassy FPO AE P, O2/OB £ubjec~! No%ice of violation, LD~ 13, Blk 3, Seimlts= Subd. #2 contamination ~0 ~he potable aquifer servin~ adjacent p~operties. As you are aware ~hi~ depar~men~ withheld approval of the wastewater system for two weeks pen~ing ~he outcome of dy~ treeing, The dye finally appeared following a threm interval. At this ~ime we h~¥e confirmed Posi~ivm dye tra¢~s in ~wo well~ on Lots 3 end ~, Block 3, Scimitar In April I called your agent, Barbara Roland, an~ inf.rm~d h~r of the s~tua~ien. She in ~u~n has con~aetmd S&$ ~nBinea~ing ~0 d~scharge of sewage effluent to groundwater is a violation of b~th s~te and municipal codes. Therefore, you are hereby"orde:ed to discontinue discharge ~rom ~he septic ~ank un~il such time ss a~ appropriate absorption pumps~ on a w~kly basic. An ins~e~Eien will be r~quire~ When You k~ve until close of bu~ine~ Wednesday, June ~, 1~93, ~o cap the tank outlet an~ provided proo~ of pumping. Failure to comply with this order will resul~ in Court action by this department. A copy of ~his order has been sent to your agent and this office will be in con,act with her to confirm Compliancm. .// look_ forward %0 a ~imely solution. ~o %).i~ problem. / Since~el~%, ,ie2 N. Bell~s On-Sihe Services We Robar~ Sharer, P.E,, S&~ db/222 DATE: TO: FROM: SUBJECT: Nitrate June 1, 1993 On-site Wastewater System Technical Review Board D.N. Bolles, On-site Services ~ and Bacterial Contamination of Potable Wells Since mid-1987, DHHS has been engaged in compiling information and investigating nitrate contamination in area wells. By 1988 it had become clear that bacterial contamination was also a factor in many of the same areas exhibiting elevated nitrate. Whereas immediate health risks are of prime concern, the data suggests a different approach concerning the way in which we view wastewater disposal. In reviewing USGS data for the past 40 years, the incidence of nitrate and bacterial contamination was found to be very low for the Anchorage area. By way of interviews with several federal and state personnel, it became evident that most thought that nitrate contamination was virtually non-existent and only rare isolated cases were known to exist. This was due in part to the wells monitored. Most of these wells are below 400 feet in elevation and thus draw from soil and bedrock aquifers with large recharge areas. This factor could lead to natural attenuation of possible contaminants. Most wells sampled within the Anchorage, Girdwood and Eagle River areas indicate nitrate concentrations average below 1.0 mg/1. It is notable that samples obtained in the mid-to late-1960's for some of the areas which now exhibit nitrate and/or bacterial contamination, indicated isolated wells with elevated nitrate concentrations (USGS 1975 Open Report). At the time of the 1975 USGS report, concern was expressed about future development of the Anchorage and Eagle River hillside areas. The possible contamination of potable groundwater was of prime concern. The report noted housing density at that time was approximately 100 homes per square mile and expected a maximum density of four to six times that amount when the area fully developed. At the time of the DHHS Huffman DeArmoun investigation the three quarters of a square mile affected had a density of 408 homes (1988 Stock Housing Maps). Page 3 Public Health Impacts The potential for localized groundwater contamination in the Anchorage and Eagle River hillsides is relatively high. The work performed by USGS (1975) and Arctic Environmental Engineers (1981) indicates a high potential for groundwater contamination exists due to shallow bedrock and groundwater, steep slopes and highly permeable soils. USGS (1975) noted that the estimated daily domestic wastewater discharge rate for the study area alone was 1.2 million gallons. Based on available data the current daily discharge rate for the same area could well exceed 3.6 million gallons. Given such a high loading rate, and data showing bacterial contamination in the Toilsome Hill, Mountain Park Est. and Scimitar subdivisions, it is apparent that negative health impacts already exist. Bacteria Canter, Knox and Fairchild (1988) pointed to highly permeable soils as a major reason for groundwater degradation. Open or gap graded soils permit the passage of biological, inorganic and organic contaminants to bedrock or groundwater virtually unchanged (Gerba; Rahe et al; & Viraraghavan). While adsorption accounts for the majority of bacteria removed temperature, pH, and soil moisture also play key roles. It is possible for bacteria to survive for extended periods in favorable field conditions. The availability of organic matter seems to be the key in survival beyond a few days. Peterson and Ward noted that some pathogenic enteric bacteria have the "potential of being transported great distances" by virtue of reducing their volume in nutrient poor environments. Thus viable dwarf cells may pass through soil pores which ordinarily would filter out the organism. Nitrate Since nitrate possesses a negative charge it is not readily attracted to soils which also possess a negative charge. As such nitrates are highly mobile in both saturated and unsaturated soils. Nitrate ions can thus move with the groundwater, migrating long distances. Walker et al, indicated the total nitrogen produced by a family of four to be between 70 and 75 pounds annually. They also noted that the "minimum area necessary" to properly attenuate 10 pounds of nitrogen, annually, to less than 10 mg/1 nitrate-nitrogen was 0.5 acres. At that rate the average lot size needed per household is 3.5 acres. As previously noted, many of those areas served by on-site septic systems, have a far greater density. Indeed most lands subdivided prior to the May, 1986, changes to Title 15 permitted development of lots less than one half acre. Hallberg and Hoyer (1982), reviewed over 16,000 test results from northeast Iowa. Their findings noted that while bacterial contamination was random as to well depth and geologic setting, nitrate contamination was significantly and systematically related to geologic settings. Page 5 The incidence of known nitrate and bacterial contamination should not be treated lightly, as if they were isolated or unrelated. High density, coupled with porous soils overlying shallow bedrock, makes for an extremely fragile environment in which to dispose of wastes and withdraw potable water simultaneously. Contaminated aquifers, in the DeArmoun-Huffman and Delucia-Scimitar areas, now contain bacteria. Residents from these areas are now having to face the consequences of septic contamination. within DHHS files there exists sufficient evidence to prove contamination of potable aquifers. Those same files further show septic systems which either lack adequate separation to, or were constructed into, groundwater and/or bedrock. The municipality at present still has the opportunity to act on this situation. The solution in some cases may be to provide public or community water and/or sewer; other areas require upgrading offending septic systems or sealing contaminated wells or aquifers. Another possibility would be to identify those areas of shallow bedrock and/or groundwater, there after requiring a manditory sand filter for all septic system installations. I sincerely hope you will encourage the department to take the lead in the development and implementation of a plan to alleviate the negative impacts of on-site sewage disposal in the Anchorage and Eagle River hillsides. References: L.W. Canter and R.C. Knox. Sround Water Oualitv Protection. 1988, Lewis Publishing, Inc., Chelsea, Michigan. N.H. Hantzche and E.J. Finnemore. Predicting Ground-Water Nitrate Nitrooen Impacts. Ground Water Vol 30, Number 4, July/August 1992. T.C. Peterson and R.C. Ward. Bacterial Retention Journal of Environmental Health, Vol 51, Number 4, 1989. in Soils April/May B.H. Keswick and C.P. Gerba. Viruses in Groundwater Environmental Science and Technology, Vol 14, Number November, 1980. 11, R.J. Perkins, Ph.D., $eptio Tanks, Lot Size and Pollution of Water Table Aquifers. Journal of Environmental Health, Vol 45, Number 6, May/June 1984. DATE: TO: FROM: June 1, 1993 On-site Wastewater System Technical Review Board D.N. Bolles, On-site Services ~ SUBJECT: Nitrate and Bacterial Contamination of Potable Wells Since mid-1987, DHHS has been engaged in compiling information and investigating nitrate contamination in area wells. By 1988 it had become clear that bacterial contamination was also a factor in many of the same areas exhibiting elevated nitrate. Whereas immediate health risks are of prime concern, the data suggests a different approach concerning the way in which we view wastewater disposal. In reviewing USGS data for the past 40 years, the incidence of nitrate and bacterial contamination was found to be very low for the Anchorage area. By way of interviews with se%eral federal and state personnel, it became evident that most thought that nitrate contamination was virtually non-existent and only rare isolated cases were known to exist. This was due in part to the wells monitored. Most of these wells are below 400 feet in elevation and thus draw from soil and bedrock aquifers with large recharge areas. This factor could lead to natural attenuation of possible contaminants. Most wells sampled within the Anchorage, Girdwood and Eagle River areas indicate nitrate concentrations average below 1.0 mg/1. It is notable that samples obtained in the mid-to late-1960's for some of the areas which now exhibit nitrate and/or bacterial contamination, indicated isolated wells with elevated nitrate concentrations (USGS 1975 Open Report). At the time of the 1975 USGS report, concern was expressed about future development of the Anchorage and Eagle River hillside areas. The possible contamination of potable groundwater was of prime concern. The report noted housing density at that time was approximately 100 homes per square mile and expected a maximum density of four to six times that amount when the area fully developed. At the time of the DHHS Huffman DeArmoun investigation the three quarters of a square mile affected had a density of 408 homes (1988 Stock Housing Maps). Page 3 Public Health Impacts The potential for localized groundwater contamination in the Anchorage and Eagle River hillsides is relatively high. The work performed by USGS (1975) and Arctic Environmental Engineers (1981) indicates a high potential for groundwater contamination exists due to shallow bedrock and groundwater, steep slopes and highly permeable soils. USGS (1975) noted that the estimated daily domestic wastewater discharge rate for the study area alone was 1.2 million gallons. Based on available data the current daily discharge rate for the same area could well exceed 3.6 million gallons. Given such a high loading rate, and data showing bacterial contamination in the Toilsome Hill, Mountain Park Est. and Scimitar subdivisions, it is apparent that negative health impacts already exist. Bacteria Canter, Knox and Fairchild (1988) pointed to highly permeable soils as a major reason for groundwater degradation. Open or gap graded soils permit the passage of biological, inorganic and organic contaminants to bedrock or groundwater virtually unchanged (Gerba; Rahe et al; & Viraraghavan). While adsorption accounts for the majority of bacteria removed temperature, pH, and soil moisture also play key roles. It is possible for bacteria to survive for extended periods in favorable field conditions. The availability of organic matter seems to be the key in survival beyond a few days. Peterson and Ward noted that some pathogenic enteric bacteria have the "potential of being transported great distances" by virtue of reducing their volume in nutrient poor environments. Thus viable dwarf cells may pass through soil pores which ordinarily would filter out the organism. Nitrate Since nitrate possesses a negative charge it is not readily attracted to soils which also possess a negative charge. As such nitrates are highly mobile in both saturated and unsaturated soils. Nitrate ions can thus move with the groundwater, migrating long distances. Walker et al, indicated the total nitrogen produced by a family of four to be between 70 and 75 pounds annually. They also noted that the "minimum area necessary" to properly attenuate 10 pounds of nitrogen, annually, to less than 10 mg/1 nitrate-nitrogen was 0.5 acres. At that rate the average lot size needed per household is 3.5 acres. As previously noted, many of those areas served by on-site septic systems, have a far greater density. Indeed most lands subdivided prior to the May, 1986, changes to Title 15 permitted development of lots less than one half acre. Hallberg and Hoyer (1982), reviewed over 16,000 test results from northeast Iowa. Their findings noted that while bacterial contsmination was random as to well depth and geologic setting, nitrate contamination was significantly and systematically related to geologic settings. Page 5 The incidence of known nitrate and bacterial contamination should not be treated lightly, as if they were isolated or unrelated. High density, coupled with porous soils overlying shallow bedrock, makes for an extremely fragile environment in which to dispose of wastes and withdraw potable water simultaneously. Contaminated aquifers, in the DeArmoun-Huffman and Delucia-Scimitar areas, now contain bacteria. Residents from these areas are now having to face the consequences of septic contamination. Within DHHS files there exists sufficient evidence to prove contamination of potable aquifers. Those same files further show septic systems which either lack adequate separation to, were constructed into, groundwater and/or bedrock. The municipality at present still has situation. or the opportunity to act on this The solution in some cases may be to provide public or community water and/or sewer; other areas require upgrading offending septic systems or sealing contaminated'wells or aquifers. Another possibility would be to identify those areas of shallow bedrock and/or groundwater, there after requiring a manditory sand filter for all septic system installations. I sincerely hope you will encourage the department to take the lead in the development and implementation of a plan to alleviate the negative impacts of on-site sewage disposal in the Anchorage and Eagle River hillsides. L.W. Canter and R.C. Knox. Ground Water Oualitv Protection. 1988, Lewis Publishing, Inc., Chelsea, Michigan. N.H. Hantzche and E.J. Finnemore. Predictinq Ground-Water Nitrate Nitrogen Impacts. Ground Water Vol 30, Number 4, July/August 1992. T.C. Peterson and R.C. Ward. Bacterial Retention in Soils Journal of Environmental Health, Vol 51, Number 4, April/May 1989. B.H. Keswick and C.P. Gerba. Viruses in Groundwater Environmental Science and Technology, Vol 14, Number November, 1980. 11, R.J. Perkins, Ph.D., $¢pti~ Tanks. Lot Size and Pollution of Water Table Aquifers. Journal of Environmental Health, Vol 45, Number 6, May/June 1984. 91-8.7 A Logical Approach to Modeling Chemical Transport in Groundwater Daniel R. Young TERRASAT Anchorage, Alaska Gary D. Runnells SOTA Environmental Technology, Inc, San Diego, California A $ S 0 C I A T I 0 N Si~c~ 1907 For Presentation at the 84th Annual Meeting & Exhibition Vancouver, British Columbia June 16 - 21, 1991 91-8,7 INTRODUCTION Groundwater models are an application of mathematical equations that attempt to explain the flow of water through sot[find rock, More complex models attempt to simulate contaminant migration associated with groundwater movement. Computer applications are developed by assigning values to the mathematical variables. Application of Models Mathematical groundwater models have many applications. They can be used to: o evaluate impacts on groundwater systems from withdrawal, injection, recharge, and contaminant releases; o simulate past or future responses of contaminant migration; o identify data gaps and needs for future investigations; o design remedlal programs and dewatering systems; o evaluate resource limits; o communicate technical information to nontechnical groups such as juries, judges, and the public o conduct environmental impact studies; and o optimize monitoring well placement and establish monitoring programs, Models can be very useful tools for evaluation and design. They canprovide rapid insight about groundwater systems, They also can provide an fmportant understanding of the processes that control contaminant migration, However, models can be expensive and misleading, The use of computer simulated models should depend on project goals, budget, and information that will be available during modeling. Conceptual Modeling A conceptual groundwater model is a summary of geological and hydrogeological information, This information describes factors that control groundwater flow, contaminant distribution and contaminant migration, Conceptual models are easier to visual ze as two- and three-dimensional graph£cs than as tables of numbers. Conceptual models are not a new idea. ecologists have been using various forms for more than several hundred years, A good example is the use of geologic cross sections. Code developers of mathematical models have mental concepts of geologlc models during code building. However, many conceptual models envisionedby the code builders are difficult for the modeling practitioner to visualize, This paper presents a practical method for developing conceptual hydrogeologic models as input to mathemat:cal models, Oraphical methods are used to develop the conceptual model, These methods allow easier communication with tecl~nical and nontechnical audiences, This approach is similar to that of Newell et al,~ who use graphical models to select parameters, The difference is that the method presented here is more site specific and less abstract, This method should help bridge the gap between the concepts envisioned by coda developers and requirements of computer applications. The methods presented here can be used for most single solute models and can be expanded to include mniti-phase and multiple solute models, 2 9I-8.7 MODEL DESIGNS Conceptual models re[~resent some or most properties of a groundwater system in qualitative terms. Mathematt~al models and computer applications reflect the conceptual model in quantitative terms and equations. Model detail depends on many factors such as available data, budget, time constraints, and severity of contamination. Conceptual models are graphical information that help describe and visualize hydrogeologie conditions, These models consist of information from sketches, cross- sections, water table contour maps, isopach maps, aerial photographs, and contaminant contour maps. Conceptualizhtg The Hydrogeologic Setting Sketches And Cross Sections. Cross sections can provide information about soil types, stratigraphy, and boundary conditions. Soil types are valuable indicators of porosity and hydraulic conductivities when pump test data ara not available, Preliminary computer simulations made from cross sections may help find gaps in available data. Cross sections also can suggest when three dimensional models are appropriate or if vertical two dimensional models can suffice. Potentiometrlc Maes. Water table maps provide a spatial representation of groundwater heads, the driving force behind most groundwater systems, Some boundary conditions can be derived from these maps such as free surface conditions, recharge, and discharge. Hydraulic gradient also can be used to estimate flow velocities. The response of potentiometric surfaces from pumping may yield information about hydraulic conductivity. Comparing potentiometric maps from different times may show seasonal changes. Isooaeh Maes, These maps represent the thickness of a geologic layer such as an aquifer or/he horizon above the aquifer. Aquifer thickness is useful to predict changes in traasmissivity, Isopach maps of overlying material may be useful for remedial and monitoring planning, These maps show the minimum depth to the aquifer, Structure Contour Mans. A structure contour map shows the topographlc surface of the top or base of an aquifer, This information can all'ow insight into boundary conditions and may help explain irregularities in flow, These maps provide a spatial view of the cross sectional information. Aerial Photo~zra~)hs, Aerial photographic interpretation eon provide information about boundaries, preferential transmisslvlty, and possible sources of contamination. Geomorphic interpretations can imply buried alluvial channels deltaic sequences or other deposits that have preferential flow characteristics. Lateral boundaries also maybe interpreted, Photos often show areas nf groundwater recharge and discharge. This information can suggest flow direction, 91-8.7 ~, Contaminant contour maps can be used to estimate contaminant dispersion by observing plume shape. Velocity is estimated by comparing[ two or more plume maps from different time events. These maps may provide information about contaminant source and give insight about timing of contaminant releases. This information is valuab}e during litigation. Scale. Visualizing a conceptual model on different scales is important. Small scale features like soil texture and porosity effect dispersion and sorption. Lithologic changes could change ionic reactions. Chemical properties like solubihty, viscosity, water partition coefficient density, and biodegradability effect contaminant transport. Moderate scale features like producing wells or soil changes can divert flow paths. Vertical or horizontal conduits could alter flow direction while allowing contamination to migrate in muitip[e paths. Large scale features like groundwater recharge areas have an effect on flow rates and routes. Recharge may be from irrigation streams, rivers, lakes, or regional scale aquifers. Features such as faults paleochanneis, rock contacts, rock fractures, and well fields can affect regional flow, Man-made features such as large paved areas may restrict or concentrate recharge. ~, Groundwater levels may fluctuate from precipitation events, These events may have a significant time lag. Recharge from these precipitation effects could change transport fluxes. Changing water tables could remobilize sorbed chemicals, Freeztng durmg winter months also affects recharge and discharge rates, Other Considerations, Developing a preliminary computer model during early stages of conceptual model building is often useful. Data gaps rapidly become apparent. Th~s process forces the modeler to think of model input during field investigations. Conceptual models help guide field investigations and evolve into more sophisticated models as new information is integrated, Identtf'v The Issues Once the modeler conceptually understands the hydrologic setting, identifying the important issues becomes the next logical step, The source of contamination may be an unresolved issue. Perhaps remediation options need to be evaluated, By identifying these issues before setting up the corn, purer model, the modeler can optimize the scale of the model to give adequate resolutmn. This is important when choosing model efficiency. Following are some examples of issues that affect model design: o Risks to groundwater resources; o Risks to surface water resources; o Known source or unknown source; and o Potential future remediation design needs 91-8.7 Quantifying Tha Conceptual Modal The task of salting up and applying a mathamatical modal is a logical step from tha conceptua modal. Numarical valuas are assigned to concaptual faatures for computar simulations. Table 1 is a partial list of input parameters for computer modeling. TABLE l SELECTED PARAMETERS REQUIRED FOR GROUNDWATER MODELING Aquifer thickness at each node, Transmissivity is directly proportional to the thieknass of an aquifen Voluma calculations for hydrauhe budgets and contaminant concentrations are also dependant on thickness. Computer simulation requires a value for aqutfar thickness at each node. Effect ve porosity Pores ty s the ra o of the pore volume to tha bulk volume of aquifer material. This parameter can be measured by collecting core samples in the field, processing them in a laboratory and averaging the results for the entire area of the computer simuqation. A more effective method s to use borehoa geophysical logging and average the results. Initial concentration at each node. So ute concentrations at observation wells and at source areas are used to begin a computer simulation, Output from one simulation can be used to start a later simulation, Initial head at each node. Most models usa elevation head data to determine flow gradients, These data are usually obtained from observation wells or piezometers, Long iud hal disparsivity, Dispersivity is a measure of the mechanical dispersion property of porous materials and is a characteristic length describing fha ability of porous materials to disperse solutes, Dispersion is proportional to velocity and ls directlonally dependent, being stronger in the direction of flow (longitudinal) than in the diraetion normal to flow (transverse), This value is estimated from the s~ze of the model and is compared with reported values from published data. Node identification parameters. These parameters include leakance concentration flow or no flow conditions constant head conditions, and recharge or discharge, Th s nformat on s der red from detai ed site characterization, Number of nodes in x-direction. Number of x-direction nodes multiplied by the x-direction spacing defines size of the s mulation. Larger numbers of nodes over a given area increase accuracy by allowing additional defimtlon of boundaries, Larger numbers increase computational time, Number of nndes in y-dlreetion. Same as nodes in x-direction except in y-direction. Number of pumping or injection wells. 91-8.7 Wells can be simulated as point sources with or without contamination or as recovery or withdrawal points, Ratio of transverse to longitudinal dispersivity. This ratio is a scaling factor that relates to plume dispersion. This parameter is estimated because elaborate tracer tests are often required for field estimates. Retardation Factor. The retardation factor is a value that represents the relative velocity of a specific solute in the groundwater. Various chemical compounds flow and adsorb at different rates within the same system. An understanding of the various components is necessary to estimate the retardation factor, Storage coefficient. The storage coefficient of an aquifer is the volume of water released from storage per unit surface area of the aquifer per unit decline of head. Storage coefficient is equal to specific yield in water-table conditions, providing that gravity drainage is complete. This is estimated from withdrawal or recovery tests. Transmissivity at each node. Transmissivit. y is a formation parameter that is derived from a well test. It represents the rate a fluid of a specific viscosity is transmitted through a cross section of unit width over the saturated thickness of an aquifer. Transmissivity is usually higher or preferential in one direction, especially in fluvial (river origin) sediment. Well tests with observation wells close to the production well or in one direction from the production well do not measure regional properties of an aquifer. Computer simulation requires a value for transmissivity at each node. T~ito Txx ratio. s ratio allows preferential transmissivity to be specified. Preferential transmissivity can be calculated from an aquifer test with observation wells in several directions or deduced from past observations of contaminant plume migration. Width of cell in a-direction and y-direction. The width of a cell is the simulation distance between nodes. Smaller widths generally yield more accurate results but increase computational time. Recharge / discharge boundaries and rate. Boundaries are important for any aquifer simulation or parameter estimation. Boundaries consist of seeps, sinks, rivers, lakes, trenches, impermeable barriers, or hydraulic connections with sources of fluid. These boundaries must be represented to specify whether fluid flows into or out of the system and the rate of flow. 91-8.7 Boundary Conditions. Boundary cond tons for groundwater flow systems are determined conceptually before mathematical made ng The best method is to use,physical hydrogeolo/~ic characteristics that effect groundwater flow. Examples ot physical boundaries ~nclude the water tab e, mpermeable surfaces surface waters and faults. The choice of boundaries is asua y arb trary and depends on scale. For example, modeling the effect of extraction wells on a small hydrocarbon plume at a service station may require exclusion of distant but rea phys cai boundar es such as major rivers. In this case, a boundary condition that simulates the effect of recharge should be selected. Specific app eatmns of var ous boundary cond t OhS are beyond the scope of this paper, For a more complete discussion of boundary conditions, refer to the publication of Frank~, Reiky, and Bennett2. A brief summary of the main types of boundary conditions follows~: Constant Head Boundary- This ty~e of boundary condition occurs where part of the surface of the aquifer is ma n tuned at an effectively constant equal head, The case where a large surface water body, such as a lake, intersects an aquifer is the cfassic example of a constant head. Specific Head Boundary- This is a boundary condition where head is specified as a function of position and me It is a general type of boundary (constant head is a special case of the specific head boundary). An example of the specific head boundary is the case of the aquifer exposed along the bed of a lar~ge stream. The stream stage remains constant at specific locations but changes with the slope of the stream channel. Use caut on when the two above boundary conditions arepresent in a model. These two types of boundaries, in effect, l?rovide un[imiteo source of water to the system, even if not realistic in the physica~ system. No-Flow Boundary- Geologic media can be regarded as impermeable by modeling when the hydrau c conduetivities differ by three or more orders of magnitude. Eaults, unfractured crystalline bedrock, and sheetpiles can be modeledas no flow boundaries. Spec f ed-F ux Boundary- This case is found when the flux across the boundary can be specified. One example of this type of boundary is aeria~ recharge, In this examp e, the flux is uniform in space and time and is called a constant flux boundary. The no-flow boundary is a special case of the specified-flux boundary. Head-Dependent F ux Boundary- As the name implies in this type of boundary, the flux across a boundary changes n response to changes in head. As an example, a semi-confining bed separating a surface water body and a confined aquifer would be a head-dependen boundary, Because as the head in the surface water body or the conf ned aquifer changed, the flux across the semi-confining layer changes. Another examp e of th s type of boundary is evapotransptration from the wa!er _ able, In both of the above cases, the change in flux is linear until a point where me flux becomes constant For he semi.confined layer a reduction in the head of the confined aqu fer nearly reduces the flux across the boundary until the aquifer head fa s be ow he bottom of the semi-confining layer. At that point the flux t~ecomes constant (seepage). Alternatively, flux due to evapotranspiration is reduced linearly as the water table falls until the point where the flux becomes zero. 9I-8.7 The fo[lowing two boundaries are only applicable to systems in which gravity drainage is a factor. Free Surface Boundary- The surface of a water table aquifer is the most common examp e of a free surface boundary. T~e surface of the water table can change with time due to changes in head at other boundaries such as changes in the areal recharge rate, Seepage-Surface- This boundary is between the atmosphere and the zone of saturation where water seeps from the ground and flows down hill, Geophysical techniques are available for efficient identification of boundary conditions. Borehole geophysical techniques are commonly( used to evaluate strat~graphic boundaries. Many surface geophysical techniques are available to investigate lateral boundaries, These techniques can provide information about contamlnam ])lume geometry, lithology, aquifer thickness variations, hydraulic conductivity~ anoeffective porosity, Potemiometric Surface, A map of equivalent heads is necessary to evaluate the flow direction and gradiem. Most mathematical models require user input of these values. A working map of the potentiometric surface can be made by contouring head data from wells and l?iezometers, Information from this map provides the input values for mathemaucal models, Hvdraulie Conductivity. Hydraulic conductivity can be measured from well tests or esilmated based on the lithology depending on the needs of the modeler, Hydraulic conductivity often varies directmnafly and spatially within an aquifer, especially in alluvial systems, Pump tests with observation wells positioned in multiple directions from the producing wellare the preferred method for determining anisotropy and measuring the hydraalic conductivity in different directions. If pump test data are not available, anisotropy can be inferred frnm observations of contaminant plume migration, ~, Transmissivity is the product of hydraalic conductivlty and aquifer thickness. Changes in aquifer thickness and hydraulic conductivity vary spatially, Accounting for directional variation is done within the mathemattcal model by entering tile ratio of the transmissivity in the x direction versus the y direction, Retardation factors. Solute proCerties, biological degradation, and adsorption are factors that affect contamination mlgratton rates. Chemical solubility limits the total concentration nature allows m a groundwater system. These limits should be verified during modeling. Adsorption is an important factor that retards the migration of solute. Adsorption depends on soilproperties such as minerals and carbon content. The degree of retardation can be estimatedby evaluating the log octanol water partition coefficient. These coefficients and chemical solubilities are available in published llteratureTM. Bindegradation is the process of microorganisms converting organic chemicals into iaorganics. Biodegradation processes may retard the rate of pl,ume mtgration. Relative rates of biodegradation are available from published literature~. Most contaminant transport mathematical models allow for retardation factors. 91-8.7 Model calibration. Models can be compared to actual data and adjusted to match observed events Changing time steps within a model creates output at the same time interva s as the actua data For example pump tests usually have a short duration so a mode may have one hour time steps. Plume hmto~, may have time intervals of one year or more. If the monitoring history is at irregular time mtervals, the model may have to be run at short time steps to match all observed events. Pump test resu ts are useful to adjust model hydraulic conductivity, storitivity, and boundary conditions, Plume h story maE help calibrate inflow, aquifer thickness, d spersion, and hydraulic conduct v ty Potentiometric maps also are useful ifpumpin.g or injection volumes are known. The calibration process is useful to observe model senmtivity (effects from changing parameters) Time steps can be set for any desired interval after the model is calibrated. The calibrated model can now be used with confidence to predict future events, past events, and to design remediation. Calibrated models can be used to dentify data gaps. Areas with missing data can be simu ated by the mode s but may show high uncertainty. These areas may be good choices for new monitoring wells, The need for more long term monitoring wells may become apparent after future migration routes are predicted. CONCLUSIONS A graph ca approach to conceptual modeling is an efficient method to obtain input for mathematical models. Graphical summaries of geological, hydrogeological, chemical, and biological data provide a framework for model parameters. Graphicalmethods inc ude structure con our maps, isopach maps, geologic maps ptume maps, cross sections, potentiometric maps and aer a photographic maps. The concepts developed from this data are easy to communicate and provide vahdation mr mathematical models. The graphical approach to conceptual modeling provides site specific information that is easy to apply to mathematical models. REFERENCES 1. C, J. Newell, L. P, .,H, opkins, and P. B. Bedient, "A hydrogeologic database for ground- water modeling Ground Water. 28 (5): 703 (1990). 2. O. L, Franke, T E Re y, and G E. Bennett Definition of boundary and intlal cond tons n the analysis of saturated ground-water flow systems - an introduction: Techniques of water resources investigaations of the U, S. Geological Survey, 1.985, Chapter B-5. 3. W. C. Walton, Practical aspects of groundwater modeling, 2nd ed., National Water Well Association, Dublin, 1985, 558p. 4. J. H. Montgomeryand L. M, Welkom. Groundwater chemicls desk reference, Lewis Publishers, Chelsea, 1989, 640p. ~ TO EDITORS Under the new federal copyright law, publication rights to this paper are 9 retained by the author(s)~ MUNICIPALITY OF ANCHORAGE COMMUNITY ;~t4',INING AND DEVELOPMENT P ,~'~. Uox 196650 Ancbornfle, Aleske 99619-66.~0 PflELIMIflAI1Y PLAT APPLICATION OFFICE UgE REC'I) BY: Please fill in lbo infommlioa reqIJested below. Pdnl one loller or number per block. f. Vm;atio, Code 2. Tax Identification No 3. Slreet Addre~ 4. HAW ahbrevinled legal de~cription (T12N R2W SEC 2 LOT 45 OR SHORT SUB BLK 3 LOTS 34). 5. [XI6TI~O abbreviated legal descriplton ( i 12bi T]2W SEC 2 LOT 45 OR SI IORT SUB 8LK 3 LO~ S 3,1) full legal on back page. 7. Pelitioner's Flepresentative Address Slate ~].~ska .... Cily. ~t)p~¢g.D ......... Stnt~ .~a~ka .... Zip .99567 10. Exl~ling I I. Geld Nm~fl)m 12 Zone Number I.ots 13 Fee$55_5.()O ................ 14. 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