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HomeMy WebLinkAboutSONNEY VIEW S-11816Sonney View 511816 Residential Well Report For: Lots 105A & Lots 120A Sonney View Subdivision NW 1/4, Section 33, T12N, R3W, SM, Alaska Prepared by: DHI Consulting Engineers 800 E. Dimond Blvd., Suite 3-550 Anchorage, AK 99515 Work Order: 09876 "2 ~.'-"" ": This report is being prepared as part of the Municipality of Anchorage's "short plat" process. The project consists of subdividing two BLM lots (lotsl05 and 120) into two new lots of 1.25 acres and 3.75 acres respectively. The new lots will be designated 105A and 120A. This subdivision does not create any additional residential lots. One of the lots (105A) is undeveloped and the other has a three bedroom residential home with an existing well and on-site septic system. When lot 105A is developed, one additional well be drilled when lot 105A is developed. To subdivide the property for which there is no public water available, On-Site Services has requested that we provide information on the likelihood of finding adequate water supply and whether there will be any detrimental effects to existing water supplies on adjacent lots when this one additional well is drilled. LOT 105A: The figures in Appendix A shows one concept on how the lot might be developed. A well can be drilled on this lot without adversely impacting the ability of adjacent lots to drill a well on their property. There are existing wells on the properties to the north, south and east of this lot. The 2.5 acre parcel to the west is undeveloped at this time. The closest developed lot to lot 105A is Lot 88B, Snow Subdivision which is adjacent to the north property line. The well on Lot 88B is approximately 300 feet north of lot 105A and slightly up gradient. The well can produce in excess of 10 gpm. It is highly unlikely that a new well on Lot 105A will have any adverse impacts on this or any other adjacent wells. LOT 120A: Lot 120A is currently developed with single family (three bedroom) residential home, driveway, onsite well and wastewater system. In our research, we found that the existing well was drilling in about mid 50's to early 60's. It consists ora 4" diameter well drilled to a depth of 76'. This well produces in excess of 10 gallons per minute. RESEARCH: Research of wells drilled on surrounding lots found that all the lots have been able to find adequate supplies ofwatcr. In general, the average static water level is around 42 feet below the ground surface (Range: 0 to 92'). The average depth of wells in the area is 106 feet (Range: 76' to 140') The average flow rate is about around 20 gpm (Range from 3.25 gpm to 100 gpm). Information on existing wells can be found in Appendix 'B'. SUMMARY: As stated earlier, only one new well will be needed as a result of this subdivision. Based on the existing well logs and well flow data, it appears that there is adequate ground water available in the area. The addition of a single new well should not adversely effect existing wells on adjacent lots. Date I I I I Onsite Wastewater Disposal I Systems Report I For: . Lots 105A & Lots 120A Sonney V~ew Subdivision I NW 1/4, Section 33, T12N, R3W, SM, Alaska I I Prepared by: DHI Consulting Engineers I 800 E. Dimond Blvd., Suite 3-550 Anchorage, AK 99515 I Date Revised: 08/12/10 Work Order: 09876 I I **.,'¢ 0~.4l. % This report is being prepared as part of the Municipality of Anchorage's "short plat" process. The project consists of subdividing BLM lots 105 and 120 (2.5 acres respectively) into two new lots of 1.25 acres and 3.75 acres respectively. The new lots will be designated 105A and 120A. To subdivide the property for which there is no public sanitary sewer available, Anchorage Municipal Code 15.65.180 establishes minimum standards for qualifying a property to support onsite septic systems. This standard requires that each lot have a minimum of 40,000 square feet. Lot 105A has 54,438 square feet. Lot 120A has 163,350 square feet. AMC 15.65.180 also requires that each lot contains sufficient area to provide for sufficient are for three subsurface disposal fields. This requirement can be met by either identifying an area on the lot that is equivalent to the areas listed in Table 2 which are based on the percolation rate of the soil or by providing the design for a septic system and two replacement areas. Lot 105A has limited area available for development (see Appendix 'A'). As such, we have elected to provided the design for an onsite wastewater disposal system and two reserve areas which will service a four bedroom residential home (see appendix A for the complete design). The soils consist of a poorly graded gravel with a percolation rate of 2 minutes/inch. The water table is about 11 feet below the ground surface. The design is based on a Class III Septic System (see Appendix 'A'). LOt 120A is currently developed with single family residential home, driveway, onsite well and wastewater system. To verify that we have enough room on the property for a future upgrade, we completed the soils investigation, which included digging a test pit, monitoring the water table, and conducting a percolation test. The soils percolation rate was 2 minutes per inch. Title 15 requires a reserve area of 10,000 square feet. Appendix 'B' shows the location and soils log of this test hole, along with the surrounding area which would be adequate to support onsite wastewater disposal systems. The existing onsite wastewater system was constructed between 1954/1955; and is still functioning very well. This system enjoys certain "grandfather" rights due to the time period in which it was constructed. The existing septic system consists of a 1000 gallon concrete septic tank and a seepage pit. The existing septic tank sets 120' from the well and 105' from the banks of Rabbit Creek. The 1000 gallon seepage pit sets 125' from the well and 70' from Rabbit Creek. These improvements are shown in Appendix 'C'. This type of system was the "standard" in the time period in which it was constructed. The general practice was to set septic tanks and seepage pits down slope from drinking water sources such as wells. There were no regulations in place at the time that this system was constructed, though there was likely information available to the public about septic system design and construction. In 1957 the Public Heath Service published the first "Manual of Septic Tank Practices" which listed a recommended set back for septic tanks from wells or sources of drinking water as fifty feet. This system was constructed to acceptable standards in use at the time and nothing related to the proposed subdivision alters the use or configuration of the existing system. Date file no. 876 Septic Repo~_8-12-10.wpd Michael N. Anderson, P.E. Civil/Structural Enginee,-ing & Construction 4661 Natrona Avenue Anchorage, Alaska 99516 Phone 345-3377 Fax 345~1391 April 21,2010 Municipalities of Anchorage Depm~ments of Health and Human Services P.O. Box 196650 Anchorage, Alaska 99519-6650 Fax 249-7847 Re: Proposed Sonney View S/D Lot 105A To Who,n it nlay COllcern: This is a request for a new septic permit on the above lot. Tile existing lot size is 2.5 acres, typical for the area and is being subdivided into one 1.25 acre lot (10SA) and tile other 1.25 ac[e being added to lot 120A, see plan.. The test bole excavation ~evealed poolly g~aded gtavel (GP) for Ihe entn'e test bole depth of I 1 feet, witb water observed arier the 7 day monitoring period at 11 feet. The pete rate was 2 minules per inch al elevation -4.0 feet. A slope of greater than 25 percent bas beeb shown on the site plan with Ibe 50 foot offset and the creek offset also. Due to tile small area available for 3 septic sites, a class ltl system has been recomme~ded. The Advantex system has been shown on the plan and profiles. Each trench is a 5-wide trench, by 20 feet long with the 10 foot separation between trenches. The trenches will need to be surveying to avoid the easement and offsets. Tbe neighboring lots will not be impacted by this new septic due to tile large lot size and excellent soils. -EAST 144T AVENUE- -NUGGET - EXlS11NG WELL 100' RADIUS / " -LOT 88A- -LO~ 87A- -LOT 8¥B-.-' - - -"-. ~ EXISTING SEFq]C '-- 7 -- -LOT 104- PROPOSED SEPT1C -LOT 106- /' MOA-VACANT ~ PROPOSEO WELL " 100' RADrUS //'LOT 105A MOA-VACANT I RABBIT CREEK -LOT ~,~OA- Septic Design Prepored for -TWILIGHT -~---SNOWSHOE LANE- r LANE- KEN ZIEGAHN PROPOSED LOT 105A SONNEY VIEW SUBDIVISION Anchorage, Alaska Michael N. Anderson, 4661NATRONA AVE, ANCHORAGE, ALASKA 99516 PH:345-3377 / FAX: 545-1391 DATE: 4/9/2010 DRAWN: D JR SCALE: 1 "=200' SHEET NO.: 1 -NUGGET LANE- I PROPOSED SEPllC SYSTEM \ ~ PROPERTY / .,/' 100' CREEK SETBACK-~ LINE -LOT 105A- OF SLOPE ~K -LOT 120A- POWER I POLE // Septic Design Prepored for KEN ZIEGAHN 100' CREEK SETBACK --.,~( PROPOSED LOT 105A SONNEY VIEW SUBDIVISION Anchorage, Alaska Michael N. Anderson, 4661 NATRONA AVE. ANCHORAGE, ALASKA 99516 PH:345-3377 / FAX: 345-1391 p. ~. DATE: DRAWN: SCALE: 4/9/2011 D JR 1 "=50' N. ANOER SHEET NO.: 2 j... -LOT 88B- ../-- PROPERLY UNE '~// . ~ ~I / / PRI~ SEPTIC TH~I/ ]../ ~ / / ~ TOP OF SLOPE I / ~ROPOS~ / ~0~ ~'~ ~(~&~ ADV~EX S~l / / ~ F~RIC / / ~ PIPE DOUB~ ~ .... -LOT 10~- il // ROCK ~.o' ~oo' ~=us~ ~ ,, ~ES~N CR~ ' o / 4 BDRM X 1~ ~ 600 gPD ~ / "[QUIRED TR~N~H~v ~ I~ (1) TRENCH J ~'~.0' DEEP 5.0' WIDE 20' LOng Michael N. Anderson, 4661 NATRONA AVE. ANCHORAGE, ALASKA gg516 PH:$45-3377 / FAX: 345-1391 Septic Design Prepared for KEN ZIEGAHN ..'t~.Y~. ............. :..~.d. ~.*, , PROPOSED LOT 105A SONNEYVIEW SUBDIVISION Ancho,-a , A, ska DRAWN: D JR SCALE: ~"--2o' ~,:~"-.. ' - !i) !h ii: ?~i i' hi /? i; - .~FROM TANK TO F1LTER ~VA~ J)M CAP ~20 POD~ ~30 INSU~ RISER ~ ~ ~1 500 ~ON ......... ~ ~,~t ~ ~ !i 1~ i~'' FRO~ ~' ~ ~ ~:b f ~ ...... , ~ TANK TO , ..... ..... '~ ..~ .... ~I .-.' ,g ~,., i:~ : FILTER 166.5" EL~A~ON ~EC~O~ NOE: ANCHO~E T~K, INC. Septic Design Prepored KEN ZIEGAHN PROPOSED LOT 105A SONNEY VIEW SUBDIVISION ~..' Anoho a , M~ch~el N. Anderson, P.E. ~ATE: ~.~MICHAEL N. ANDERSON/~ 4661 NATRONA AVE. DRAWN: D JR ~;~-,.,, No. CE 9~69 ./'~ PH:~45-5377 / FAX: 545-1591 SHEETNO.: 4 Pedormed For: Legal Description: 6- 7- 8- 9- 10- 12- 13- 14- Municipality of Anchorage Development Services Department Building Safety Division On-Site Water and Wastewater Program 4700 Elmore Road P.O. Box 196650 Anchorage, AK 99507 . .www.cLanchmaqe,a k. us (g07) 343-7904 Soils Log - Percolation Test 16- 17- 18- 19- WAS GROUND WATER ENCOUNTERED? IF YES, AT WHAT DEPTH? // L Depth to Water After " O Mo.itoting? /{ / EP Date: ,/~¢ Date Pedorm Township, Range, Section: Sile Plan Reading Date Gross Time Net Time Depth ID Water Net Drop · , TEST RUN BETWEEN FT AND CERT FY THAT TH S TEST WAS PERFORMED IN ACCORDANCE WITH ALL STATE AND MUNICIPAL GUIDELINES IN EFFECT ON THIS DATE. DATE: ,. (¢/~ SV~tHV qq~tM (INV DI£d~tS © NUGGET LANE PP N 89'58'01" e 279.83 `35' BLM ROADWAY & PUBLIC U~LITY EASEMENTS 0 0 Z ~.~5 AC. RESERVE AREA 11,2~7 S.F. BLM ROADWAY & PUBLIC UTILITY EASEMENTS ~"~ ...... ..~-..-"'1" 89'58'21" W /,<N 89'5T55" W 329.82 529.B2> NOTES ) CONTOUR INTERVAL IS 2' 2) RABBIT CREEK AND OTHER IMPROVEMENTS ARE SHOWN PER FIELD SURVEYCOMPLETED BY DHI CONSULTING ENGINEERS .3) THE CROSS HATCHED AREA REPRESENTS THE SEPTIC AREA NEEDED TO COMPLY WITH TITLE 15,65.180. PROVIDED -- 11,267 SF REQUIRED = 10,000 SF BLM ROADWAY &: PUBLIC UTILITY EASEMENTS TWILIGHT LANE 0 II lO ~ zO DEDICATED R.O.W LOT 120A, SONNI~.Y VI]~ SUBDMSION SEPTIC AND WELL AREAS Pedormed For: Legal Description: I 10. 11. 15- I 17- 18- I 19- 20- I COMMENTS Municipality of Anchorage Development Services Department Building Safety Division On-Site Water and Wastewater Program 4700 EImore Road P.O. Box 196650 Anchorage, AK 99507 www.cLenchomae,ak,us (907) 343-7904 Soils Log - Percolation Test L ' W/~$ (~ROUNO WATER ENCOUNTERED? IF YES, AT V~-IAT DEPTH? Depth ~ W~er After Reading Date Gross Time Net Time Depth to Water Nel Drop III PERCOLATION RATE ~ (r~n~teu~r¢~) PERC HOLE DIAMETER TEST RUN I~ETWEEN ~ ~T AND ~ FT PERFORMED IN ACCORDANCE WITH ALL STATE AND MUNICIPAL GUIDELINES IN EFFECT ON THIS DATE. DATE: