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Home My WebLink AboutCOUSENS #1 S-12236Cousens #1 512236 GARNESS ENGINEERING GROUP, Ltd CIVIL & ENVIRONMENTAL ENGINEERS - April 13, 2016 Municipality of Anchorage Development Service Department On-Site Water & Wastewater Program 4700 Elmore Road Anchorage, AK 99507 Attention: Deb Wockenfuss Subject: Soils Investigation Report and Well/Septic Reserve Area for the Proposed Subdivision of Cousens Subdivision, Addition #1; Lots I and 2 (Case # S12236) Located at Mile 5.2 off Eklutna Lake Road in Chugiak, Alaska Mrs. Wockenfuss, Cousens Subdivision; Tract A is located at mile 5.2 off Eklutna Lake Road in Chugiak, Alaska. Based on the preliminary plat drawing provided to us, the subdivision of Tract A will consist of two (2) lots and will be called Cousens Subdivision, Addition #1, Lots 1 and 2. We have excavated and logged test holes on each proposed lot that will be used to establish septic reserve areas for each lot in the subdivision. PROPOSED WELL AND SEPTIC RESERVE AREAS We have prepared soil logs for all test holes (see attached). Per MOA wastewater ordinance AMC 15.65.180, we are required to provide a site map showing a septic reserve area for each lot that meets the requirements set forth in Table 2 of AMC 15.65.180 (see below). TABLE 2 TABLE INSET: Percolation Rate Total Reserved Area (square (minutes/inch) feet) 1--5 10,000 5--12 12,000 12--24 14~000 24--60 16~000 3701 East Tudor Road, Suite 101 * Anchorage, Alaska 99507-1259 Phone: (907) 337-6179 * Fax: (907) 338-3246 * Website: www.gamessengineering.com Page 2 of 3 The percolation result for test hole #1 (proposed Lot 1) was 9.2 minutes/inch and 1fie percolation result for test hole #2 (proposed Lot 2) was 5 minutes/inch. Based upon Table 2, proposed Lot 1 requires a septic reserve area of 12,000 square feet and proposed Lot 2 requires a septic reserve area of 10,000 square feat. Attached is a site plan which shows the septic reserve area for each lot. As can be seen on the site map, which has topographical information established by S4 Group, the slopes within the septic reserve areas range betwean 25% to 30%. There appears to be sufficient area for a structure, driveway, wall, and onsite wastewater disposal system for each lot. As can be seen on the site plan, there is an existing house on the original property that was built in 1962. The house has only a 1 bedroom. The original homesteader, Allan Cousens, still owns the properbj and lives on property. This existing 1 bedroom is served by a sub-surface water collection system and an undocumented septic system. We have discussed this project with you and you stated to us that wa needed to either prove the existing septic system was not causing a health dsk by performing a test hole and showing it met separation distances to groundwater and bedrock, or document the existing septic system. Per the request of our client, we performed a test hole near the existing septic system to verify groundwater and bedrock conditions. According the owner of the house, the existing septic system consist of a septic tank and a drainfield that utilizes Infiltrator chambers. We measured down the monitoring tube atthe end of the drainfield and found the drainfield was ~4 feet deep on the Northwast end of the drainfield. Based upon our findings in the test hole, no bedrock was encountered to 14.5 feat deep and after 7-day groundwatar monitoring, water was found to be at 12.5 f~et below the ground surface on 4/7/2016. Based upon these levels, the drainfield has 6+ feet separation to the bottom of the test hole and 5+ feet to the groundwater level (5 feet separation required for the month of Apdl per MOA Onslte policy). We would like to note that wa did find on the day of our site visit on 3/'30/2016, the drainfield was operating above the design effective depth of Infiltrator chambers. However, there was no indication of back-up in the foundation cleanout at the house and there was also no indication of surfacing effluent. We are requesting that your department allow the property be subdivided using the septic reserve areas shown on the attached site plan and not require the documentation or upgrade of the existing septic system. SLOPE WAIVER REQUEST FOR SEPTIC RESERVE AREAS: As can be sean on the site plan, the average slopes within the septic reserve areas range from 25 to 30 percent. We are requesting a waiver for each lot to allow the septic reserve areas to be used for these slope conditions. The following are mitigating factors for justification of these waivers: · Based upon the percolation results, the porosity of the soils is good and will promote rapid downward movement versus lateral movement of the effluent. · The existing drainfield as stated is in a surcharged condition and based upon our site investigation, there is no indication of daylighting downhill from the drainf'~ld. · The slopes below the platted drainfield sites are heavily vegetated. · The property is in an area with very Iow population density and the property downhill of the septic reserve areas is Chugach State Park land. Given these mitigating factors, it is our opinion that there is minimal risk with the granting of these waivers. 3701 East Tudor Road, Suite 101 * Anchorage, Alaska 99507-1259 Phone: (907) 337-6179 * Fax: (907) 338-3246 * Website: www. garnessengineering.com Page 3 of 3 WATER AVIALABILITY: We have performed records reseamh on some of the surrounding properties and have attached the well logs and other well information. There are only two (2) wells in the near vicinity of the property. The well log for the property directly uphill from the proposed subdivision is 180 feet deep and had a flow rate of 20 gpm with a static water level of 37 feet. Based upon this well log and that the proposed wells are downhill from this well, it is assumed that there should be no issues with water availability with only two (2) additional well to be drilled in the area. If you have ~, e/~I~/ J effre/~/,~(,O~? Pre~i.~lCt ~estions, please contact us at 337-6179. ;, P.E., M.S. 3701 East Tudor Road, Suite 101 * Anchorage, Alaska 99507-1259 Phone: (907) 337-6179 * Fax: (907) 338-3246 * Website: www. gamessengineering.com · 30+ FEET TO DAYLIGHTING OF IMAGINARY SLOPE · ~-~ NOTE: THIS IS A GENERIC DRAWING SHOWING THE ~5 WIDE ~"=~' PROFILE D~WlNG FOR SLOPE WAIVER FOR LOT 1', COUSENS S/D o o SLOPE REQUIREMENTS FOR A POSSIBLE DESIGNj ~ - -BOWOM OF TEST HOLE ~2 ~ 14.5 FEET - NO BEDROCK OR IMPERM~BLE SOILS I SCALE: PROFILE D~WING FOR SLOPE WAIVER FOR LOT 2; COUSENS S/D / GARNESS ENGINEERING GROUP Ltd ~ClVIL & ENVIRONMENTAL ISOIL LOG - PERCOLATION TEST I LEGAL DESCRIPTION: COUSENS S/D; TRACT A (PROPOSED LOT 1 ) PERFORMED FOR: FRED COUSENS DATE; 10130/2015 ORGANICS ITEST HOLE #1 I SOIL CLASSIFICATIONS GH HARDER WITH DEPTH SOILS LOGGED BY: JODYMAUS COHMENTS: ORG ML CL OL MH CH OH SC DEPTH TO DATE GROUNDWATER DRY 10/30/2015 DRY 11/3 &11/13 11,5' 4/7/2016 12' 5/3/2016 SITE PLAN SCALE: DATE READING CLOCK NET TIME WATER LEVEL NET DROP TIME (MINUTES) READING (INCHES) 11/3/2015 I 1:26 6" 2 1:56 30 2-3/4" 3-1/4" 3 1:56 6" 4 2:26 30 2-3/4" 3-1/4" 5 2:26 6" 6 2:56 30 2-3/4" 3-114" PERCOLATION RATE 6.2 (HIN./INCH) PERC. HOLE DIA. TEST RUN BETWEEN 5.0 FT. AND 6,0 FT. A FOUR HOUR PRESOAK WAS PERFORHED: I YES [~NO PERCOLATION TEST PERFORHED BY:. JODYMAUS PERCOLATION READINGS ARE WITHINI~6OFINCH. 6 (INCHES) PERFORMED BY GEG. Ltd. I, JEFFREY A. GARNESS, CERTIFY THAT THIS WAS PEREOIRMED IN ACCORDANCE WITH ALL STATE AND MUNICIPAL GUIDELINES IN EFFECT ON THIS DATE: GARNESS ENGINEERING GROUP, Ltd .... E.T[JOORRO~D, SUITE 101' C~V~L ~[ .EpNV'RONM.ENTAL EN.~N~ERgSm ............ ~c]o~ ' ' H LEGAL DESCRI~ION: COUSENS S/D; T~CT A pERFORMED FOR' FRED COUSENS DATE' 3/3012016 (SM) GM HARDER WITH DEPTH ITEST HOLE #2 I 80IL CLA881FICATIONS DEPTH TO GROUNDWATER DATE DRY 3/30/2016 DRY 3/31/2016 12.5' 4/7/2016 10' 5/3/2016 SITE PLAN ORG ["IL CL OL MH Qx~* sc SCALE: DATE READING CLOCK NET TIHE WATER LEVEL NET DROP TINE (MINUTES) READING (INCHES) 3/31/2016 I 12:20 6" 2 12:50 30 0" 6" 3 12:50 6" 4 1:20 30 0" 6" 5 1:20 6" 6 1:50 30 0" 6" SOILS LOGGED BY: JODYMAUS COHHENTS: PERCOLATION READINGS ARE WITHIN 1/16 OF INCH. PERFORMED BY GEG, Ltd. I, JEFFREY A. GARNESS, CERTIFY THAT THIS WAS PEREOEMED~ IN ACCORDANCE WITH ALL STATE AND MUNICIPAL GUIDELINES IN EFFECT ON THIS DATE: PERCOLATION RATE 5 (MIN./INCH) PERC. HOLE DIA. TEST RUN BETWEEN 5.0 FT. AND 6.0 FT. A FOUR HOUR PRESOAK WAS PERFORMED: I YES D NO PERCOLATION TEST PERFORMED BY: JODYMAU$ 6 (INCHES) Municipality of Anchorage .P.O. Box 196650 ® 4700 Elmore Road Anchorage, Alaska 99519~6650 ® (907) 343-7904 ® Fax (907) 343-7997 .http:llwww.muni.or,qlOnsite Development Services Division On-Site Watei' and Wastewater Proqram **** VARIANCE/WAIVER REVIEW **** Waive~: OSV16t058 COSA#: Permit#: PID#: 052-381-04 Legal Description: Cousens #'i L2 Pro osed Engineer: Garness Engineering Group Applicant: Fred an._~d Alien C_o. usens Your request for a waiver of the required 50 feet horizontal separation from the subdivision septic reserve area to the excessive slope has been approved. The approved separation distance is 0.0 feet. This waiver approval may be used for a septic permit if; A. The slope is the same as submitted for review, B. The distribution pipe is at the same depth and C. Soils and groundwater levels are the same. [] The affected adjacent property owner(s) have been given a 7 day notice regarding this waiver. [] Notarized letter(s) of nonobjection have been received from the owner(s) of the affected adjacent property. [] Adjacent properties are not affected by this waiver. Waiver is Granted: X Waiver is not Granted: · Name of Revig~r **** VARIANCE/WAIVER REVIEW **** Municipality of Anchorage p.O. Box 196650 · 4700 Efmore Road Anchoraqe, Alaska 99519-6650 ® (907) 343-7904 · Fax (907) 343-7997 http:llwww.muni.orqlOnsife ,Development Services Division On-Site Water and Wastewater Proqram **** VARIANCE/WAIVER REVIEW **** WaiverS: OSVt61057 COSA#: _ PID#: 052-38%03 Legal Description: Cousens #1 L1 Pr.~.~osed Engineer: Garness Engineering Group Permit#: Applicant: Fred and Allen Cousens Your request for a waiver of the required 50 feet horizontal separation from the subdivision septic reserve area to the excessive slope has been approved. The approved separation distance is 0.0 feet. Tiffs waiver approval may be used for a septic permit if; A. The slope is the same as submitted for review, B. The distribution pipe is at the same depth and C. So)ls and groundwater levels are the sam& [] The affected adjacent property owner(s) have been given a 7 day notice regarding this waiver. [] Notm'ized letter(s) of nonobjection have been received from the owner(s) of the affected adjacent property. [] Adjacent properties are not affected by this waiver. Waiver is Granted: X Waiver is not Granted.' **** VARIANCE/WAIVER REVIEW ****