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Home My WebLink AboutSECLUSION S-11579Seclusion 511579 ROBERT DR -- NICKLI STEER II w Z w May 23, 2010 Municipality of Anchorage Building Safety Division On Site Water and Wastewater Program 4700 Elmore Street Anchorage, AK 99507 Attention: Debbie Wockenfuss Su~e~: Seclusion Subdivision, S-11579-2 Septic System Feasibility Study Dear Debbie: The owner of Tract lA, Paine Subdivision intends to subdivide the tract into four lots. The four lots front along Paine Road and are designed around the existing Lot 2, Paine Subdivision. The new subdivision will be known as Seclusion Subdivision. Three of the four lots exceed 7.26 Acres in surface area with the fourth lot 4.76 Acres. All four lots will be served by a common access driveway which extends from the northeast corner of the subdivision to the westerly Lot 1. The subdivision is located immediately south of Paine Road in the Bear Valley area of South Anchorage. The ground surface of the lots slopes steeply from Paine Road at varying grades in a southerly direction to the southern boundary of the subdivision. This slope is approximately 25% to 35% for the first 500' and then becomes much steeper. All septic systems proposed for the lots will be placed in areas where the surface slope is less than 35%. The cross slope on the property is nearly flat. The proposed absorption systems and reserve areas are placed parallel with the contours at locations where the slope is the shallowest. Test holes were placed on the proposed lots in July and August of 2006. Water monitoring has been ongoing with readings last taken on May 20, 2010. The purpose of the test holes was to assess the underlying soil conditions and to determine whether septic systems could be placed on the lots to serve single-family homes. The test holes were placed to depths of up to 16' with no bedrock or impermeable lenses of material encountered. The locations of the test holes were determined in the field by the developer for ease of access and to prevent destruction to the existing trees and fragile Seclusion Subdivision May 23, 2010 Page 2 terrain. At the time of the exploration access was off of Paine Road with only a slight intrusion into the new subdivision. Percolation benches were constructed at various depths in the holes, but primarily 4' to 5' below the original ground surface. A percolation cavity was prepared to determine the absorptive characteristics of the soils encountered. The cavity was presoaked in accordance with Municipal requirements and a percolation test performed. The results of the tests are included in the attached documentation. In every case silty gravel (GM/ML) with varying degrees of silt was encountered to the bottom of each test hole. The percolation rate in this material ranged from 16 to 97 minutes per inch. All lots have percolation rates which qualify for use with the Category III septic systems. All work was completed under the direction of technicians and engineers at Anderson Engineering. The results of the percolation tests and test hole logs are included as well as the water monitoring results. A monitor tube remains in place in each hole to determine the groundwater elevation over a period of time. Water was found in all test holes and is probably attributable to surface runoff. The highest noted depth of groundwater was 6.6' below the surface. The steepness of the slopes, will not allow the use of conventional gravity flow septic systems on the lots. We therefore required the use of the Category 3 Nitrate Reducing septic systems like the Advantex Treatment System as previously approved for use on Grandeur Subdivision to the south where steep slopes are also found. In this case however no bedrock was encountered in any of the test holes as opposed to Grandeur Subdivision. In addition, any home to be constructed on the lots will be limited to four (4) bedrooms through a plat note. An application rate of 1 gallon per day per bedroom was utilized to design the absorption trenches for Lot 4, which is the only lot not affected by the 100' ditch setback along Paine Road. The remaining three lots are affected by the setback and all septic systems on these lots must be a minimum of 100' from the ditch. We are therefore recommending reserve areas for Lots 1 through 3. The size of the reserve areas is 16,000 square feet for Lots 2 and 3 and 22,000 square feet for Lot 1. The new absorption trenches were designed for a four (4) bedroom home with an application rate of 2 gallons per day per square foot. They are 40' long by 5' wide with an effective depth of 4'. The total depth of the trenches is 6' which places the bottom of the trenches 6' above the water table recorded on October 15, 2006 They are not located more than 50' from any break in grade greater than 25%, but the use of the nitrate reducing system allows the placement of the trenches at these locations.. Based on our field study and water monitoring completed to date it appears Lots 1 through 4 of the proposed Seclusion Subdivision are capable of supporting an onsite septic system and well. The size of the homes to be constructed on the lots must be limited to four (4) bedrooms. Additional test holes and percolation testing will be completed during the permitting phase for development of the individual lots. We are Seclusion Subdivision May 23, 2010 Page 2 confident suitable absorption areas will be found in the reserve areas designated for each lot. We are recommending a plat note be added stating that the reserve areas were establish based on one test hole per lot and that additional testing will be required prior to the issuance of a septic system permit. Copies of the test hole logs, percolation tests, test hole location map and the contour map showing the surface topography of the property are included for your use. We hereby request your approval of Seclusion Subdivision as designed with the septic systems and reserve sites at the locations shown. The absorption trenches will be placed on the final plat along with the plat notes stating the requirement for the nitrate reducing systems and the limitation of home size to 4 bedrooms. A final note stating no driveways or permanent structures may be placed over the septic sites will also be added. Sincerely, Michael E. Anderson, P.E. Attachments DEPTH (fee0 1 2 3 4 5 6 7 8 9 11 15 16 17 18 19 2O 4700 MUNICIPALITY OF ANCHORAGE DEVELOPMENT SERVICES DEPARTMENT BRAGAW STREET ANCHORAGE, AK 99519-6650 SOILS LOG - PERCOLATION TEST LEGAL DESCRIPTION: SECLUSION SUBDIVISION, LOT PERFORMED FOR: JOE BURNHAM DATE: 7/28/00 PROJECT No.: PARCEL ID#: TECHNICIAN: A. HARALA SLOPE OB/OG SILTY GRAVEL WITH VARYING SiLT GM/ML BOH @ 12' SITE PLAN SEE SITE PLAN WAS GROUN'D WATER ENCOLrbrfBRED? YES (,MINUTES) I (MINUTES) (INCHES) (INCHES) 7/29 TEST HOLE PRESOAKED PRIOR TO TESTING: i I 11:49 2.0" 2 12:19 50 2.31" .31" 5 12:21 1.94" 4 12:51 50 2.25" .51" 5 12:52 2.0" 6 13:12 30 2.51" .31" PERCOLATION RATE: 97 .(MU'a/INCH) PERC. HOLE DIA. 8" fINCHES TEST RUN BETWEEN: 4 FT. and 5 FT. COMMENTS: TEST HOLE PRE SOAKED PRIOR TO TEST. TEST PERFORMED BY ANDERSON ENGINEERING. I, MICHAEL E. ANDERSON CERTIFY THAT THIS WAS PERFORMED IN ACCORDANCE WITH ALL STATE AND MUNICIPLE GUIDELINES IN EFFECT ON THIS DATE. 5/23/2010 4700 DEPTH (feet) 1 2 3 4 5 6 7-- 8-- 9 11 15 16 17-- 18 19 20 I~IUNICIPALITY OF ANCHORAGE DEVELOPMENT SERVICES DEPARTMENT BRAGAW STREET ANCHORAGE, AK 99519-6650 SOILS LOG - PERCOLATION TEST I LEGAL DESCRIPTION: SECLUSION SUBDIVISION, LOT 2 PERFORMED FOR: JOE BURNHA[W DATE: 7/28/06 PROIECT No.: PARCEL ID~: TECHNICIAN: OB/OG SILTY GRAVEL <15% SILT GM A. HARALA SLOP[ WAS GROUND WA~.R ENCOUNTERED? NO BOH @ 14' SITE PLAN SEE SITE PLAN DATE 7/29 GROSS TIME NET TIME %~,~I~RT0 [NET DROP READING (MINUTES) (MINUTES) (INCHES) (INCHES) TEST HOLE PRESOAKED PRIOR TO TESTING: i 11:59 4.25" 2 12:29 50 6.58" 2,12" 5 12:,58 4.19" 4 15:08 30 6.12" 1.94" 5 15:10 4.25" 6 13:40 50 6,12" 1.88" PERCOLATION RATE: 1 6 .(~aN/n'4CH) PERC. HOLE DIA. 8" _0NCHES) TEST RUN BETWEEN: 5 FT. and 6 FT. COMMENTS: TEST HOLE PRE SOAKED PRIOR TO TEST. TEST PERFORMED BY ANDERSON ENGINEERING. I, MICHAEL E. ANDERSON CERTIFY THAT THIS WAS PERFORMED IN ACCORDANCE WITH ALL STATE AND MUNICIPLE GUIDELINES 1N EFFECT ON THIS DATE: 5/25/2010 &700 [ DEPTH (feet) 1 2 3 4 5 6-- 7-- 8 9 11 15 16 17 18 19 20 MUNICIPALITY OF ANCHORAGE DEVELOPMENT SERVICES DEPARTMENT BRAGAW STREET ANCHORAGE, AK 99519-6650 SOILS LOG - PERCOLATION TEST SECLUSION SUBDIVISION, LOT LEGAL DESCRIPTION: PERFORMED FOR: DATE: 7/27/06 PARCEL ID#: OB/OG SILTY GRAVEL GN JOE BURNHAM PROJECT No.: TECHNICIAN: A. HARALA SLOPE SITE PLAN SEE SITE PLAN BOH @ 14' WAS GROUND WATER ENCOUNTERED? YES IF yES @ WHAT DEIrFFI?. 13.5' DEPTH TO WATER AFTER MONITORING: 6.6' DATE OF MON/TOK1NG:. 5/20/10 DATE READ NG GR. OSS TINE NET TINE %~,~F~RTM NET DRQP I ~M'N"TES) I(M'NUTES) I ('NC"ES) I 7/28 TEST HOLE PRESOAKED PRIOR TO T~STING: I 12:18 2.88 / /2 ,2:~8 3o ~.o6,, ,.,~,, / I 3 '~:~ / I ~' ,~:2~ ~o ~.o,, ,.~,, / / ~ ';:~ ~'~" / 6 1&:22 50 A. 19" 1.51" eg~CO[A~O~ ~: 26 .~C~ eg~C. ~Og~ ~. 8" .(~C~S) TESTR~BET~EN: 4.5 FT. ~d 5.5 FT. COMMENTS: TEST HOLE PRE SOAKED PRIOR TO TEST. TEST PERFORMED BY ANDERSON ENGINEERING. I, MICHAEL E. ANDERSON CERTIFY THAT THIS WAS PERFORMED 1N ACCORDANCE WITH ALL STATE AND MUNICIPLE GUIDELINES IN EFFECT ON THIS DATE:. 5/23/2010 4700 [ DEPTH (feet) 1 2 3 4 5 6 7 8 9 11 15. 16 17 18 19 2O MUNICIPALITY OF ANCHORAGE DEVELOPMENT SERVICES DEPARTMENT BRAGAW STREET ANCHORAGE, AK gg51g-6650 SOILS LOG - PERCOLATION TEST LEGAL DESCRIPTION: SECLUSION SUBDIVISION, LOT PERFORMED FOR: JOE BURNHAM DATE: 7/27/06 PROJECT No.: PARCEL ID#: TECHNICIAN: ITEST HOLE No. 4 ] 0B/0G SILTY GRAVEL GN WAS GROOlqD WATER BNCOLrN2~KED? __ B0H @ 13' A. HARALA SLOPE No 2 30 3 4 30 SITE PLAN SEE SITE PLAN DATE OF MONITORI[NG: 5/20/10 DATE DEPTH TO READING GROSS TINE NET TIME WATER NET DROP (MINUTES) (MINUTES) (INCHES) (iNCHES) 7/28 TEST HOLE PRESOAKED PRIOR TO TESTING: 4.44" 5,12" .69" 4.56" 5.19" .63" 5 4.5" 6 5.06" .56" 12:33 13:03 IS:lA 15:&4 15:46 14:16 30 __.(rNcims) PERCOLATION RATE: 53 (MiN/INCH) PERC. HOLE DIA. 8" TEST RUN BETWEEN: 4.5 FT. and 5.5 FT. COMMENTS: TEST HOLE PRE SOAKED PRIOR TO TEST. TEST PERFORMED BY ANDERSON ENGINEERING. I, MICHAEL E. ANDERSON CERTIFY THAT THIS WAS PERFORMED IN ACCORDANCE WITH ALL STATE AND MLrNICIPLE GUIDELINES IN EFFECT ON THIS DATE:. 5/23/2010 Municipality of Anchorage Development Services DepaKment Building Safety Divisi~ On-Site Water and Wastewater Prcgram ' 4700 FJmore Road P,O, Box 196650 Anchorage; AK 99607 www. ci.an chomge.ak,us (~07) 643-7904 Soils Log Percolation; Test Joe Burnham: Date P~o~.' ~~~ Seclusion Subd., Lot 1 '~ To~hip, Ran~., 2: 3- 9- 13- 14- 15- ~72 20- Site Plan Reading Date Gr~s Time Net Time Depth to W~ater Net Drop AND '~ FT PER FORMED BY:/~,''~, I cER TI P( THA:I' THI~ TEST WA~S PERFORMED IN ACDORDANCE WITH ALL STATE AND MUNICIPAL GUIDELINES IN EFFECT ON THIS DATE. DATE: Municipality of Anchorage Develooment Services Department BuiJding Safety Division On-Sife Water and Wastewater Program P.O. Box 106650 AnchOrage, AK 99507 (007) 343-7904 Soils Log - Percolation Test . , ~=do~ed For Joe Burnham Date Pe~o~: Legal D~cdp~on: Seclusion Subd., Lot 1 Township, Range~ So.ion: Si~e P~an 6- 7- 8- 9- 13- 14- 15- 16- 17- 18- 19- 20- ENCOUNTERE F YES. AT WHAT DEPTH? Depth to Wator After -~r_ / p Monitoring? E Reading Date Gross Time Net Tlrqe Depth to Water Net Drop ·/ II:,f-.-- ¢,~ ~1~ ~,,c,'t'" PERCOLATION RATE ,~z~ (minute~nch) PERC HOLE DIAMETER AND '~ PERFORMED BY: .~ ~...,~ [ CERTIFY THAT THIS TEST WAS "PERFORMED IN ACCORDANCE WITH ALL STATE AND MUNICIPAL GUIDELINES IN EFFECT ON THIS DATE. DATE:¢ ANDERSON ENGINEERING P.O, BOX 240773 ANCHORAGE, AK 99524 522-7773 677-7766 (FAX) June 27,2010 Municipality of Anchorage Building Safety Division On Site Water and Wastewater Program 4700 Elmore Street Anchorage, AK 99507 Attention: Debbie Wockenfuss Subject: Seclusion Subdivision, S-11752 Water Availability Study Dear Debbie: We have collected information on several wells in the area of the proposed Seclusion Subdivision to estimate the possible depths and production rates of wells to be constructed in the future on Lots 1 through 4. Field investigations indicate a combination of wells constructed without the presence of bedrock and others indicating bedrock at depths exceeding 40'. In all cases the well are shallow in comparison to most wells in the Anchorage area with the deepest at 183' and the shallowest at 55'. No information is available on Lot 2, Paine Subdivision which falls in the confines of Seclusion Subdivision. It is thought to be fairly shallow with sufficient production to support the house. The well on Lot 1, Gallagher Subdivision directly east of Seclusion is cased to a depth of 111'. No exact depth of the well is known, but a recent production test indicated a yield of 5.6 gallons per minute. The well on Lot 3, Gallagher Subdivision approximately 300' east of Seclusion has a well 135' deep with a production rate of 1.5 gallons per minute. The ground elevation at the well head is similar to the elevation where wells would probably be constructed in Seclusion Subdivision. Little information could be found on the wells located immediately south of Paine Road. It is known the wells have been in use for many years and no shortage of water has been reported. Lot 10, Block 10 Rabbit Creek Heights Subdivision is directly across Paine Road from Lots 2 and 3, Seclusion Subdivision. The well on this lot is 183' deep and produces 3.5 gallons per minute according to the well log. Lot 9 immediately west of this lot and directly across from Lot 2, Seclusion is 130' deep with a production rate of Seclusion Subdivision June 27,2010 Page 2 4.0 gallons per minute noted on the well log. Two production tests have been performed in the past on the well which indicate 3.8 and 3.0 gallons per minute, A breakdown of the wells in the area with their respective production rates follows: SECLUSION SUBDIVISION WATER AVAILABILITY STUDY WELL LEGAL DESCRIPTION DEPTH PRODUCTION - LOG PRODUCTION - TEST Gallagher, Lot 1 >111' 5.8 GPM Gallagher, Lot 3 135' 1.5 GPM King Heights, Lot 3 127' 8.0 GPM 5.25 GPM Hunter Heights, Tract 1 90' 5.0 GPM Cinerama, Lot 17 212' 40 GPM Mountain Vale, Lot 2A 83' 20 GPM Mountain Vale, Lot lA 83' 10 GPM Mountain Vale, Lot 4 >49' 3.5 GPM Mountain Vale, Lot 5 11.0 GPM 5.25 GPM Rabbit Creek Hts, Lot 8A 160' Unknown Rabbit Creek Hts, Lot 10 183' 3.5 GPM Rabbit Creek Hts., Lot 9 130' 4.0 GPM 3.8/3.0 GPM No development has yet occurred to the immediate west of Seclusion Subdivision nor is there any development to the south or southwest. Grandeur Subdivision will soon be developed to the southwest which will provide further indications of the well depths and productions to be expected on Seclusion Subdivision. Surface water in the form of Rabbit Creek runs through the area and to the northeast of Seclusions Subdivision. The presence of Rabbit Creek and the watershed area surrounding the Bear Valley area contributes to the shallow aquifer apparently serving the area. Runoff from the mountains surrounding the area is noted year round constantly replenishing the aquifer. Seclusion Subdivision June 27,2010 Page2 It is obvious from our study that any wells to be constructed Seclusion Subdivision in the future will be placed to depths of less than 200' and will probably be founded in bedrock. The depth of the bedrock is unknown, but may exceed 50'. It is also possible bedrock may not be found as noted on Lot 3, Gallagher Subdivision which indicated no bedrock to 135'. The production rates will be sufficient to support a four bedroom home and can be expected to be between 2 and 5 gallons per minute. Sincerely, Michael E. Anderson, P.E. Attachments 4A RABBIT CREEK HEIGH' BLOCl REEK LOT 7 CINERAMA BLOCK 2 TR D MO INTAIN LOT 6 LOT 5 LOT 4 LOT 3 VACANT PAINE: ROAD Lof 1 Lof 2 Lof 3 \$\0~ LOT 1 Lof 4 GAL LOT ,~ VACANT WATER AVA I LA BI LITY SCALE 1" = 200' PLAN LOT 2 LOT 1