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Home My WebLink AboutMILLPLACE ESTATES S12557Onsite File September 11, 2020 UE E E R I N G Municipality of Anchorage — Building Safety On Site Water and Wastewater Program 4700 Elmore Street Anchorage, AIC 99507 Attention Subject: Dear Deb: Deb Wockenfuss PO BOX 240773 ANCHORAGE, AK 99524 522.7773 677-7766 (FAX) FORGECIVIL.COM S12557 - Millplace Estates Subdivision Septic System Feasibility and Water Availability Study 49 Benjagi'rySchiller 9/11/202, �'pROFESSIOHP .� A petition has been submitted to subdivide two lots into three, forming the new Millplace Estates Subdivision. We our presenting our findings that each new lot will have sufficient area and potential for on-site wells and septic systems. The property in general is moderately sloped towards the west, primarily at grades ranging from 2-15%. Most of the area is under 10%, with just the southeast corner showing steeper slopes that approach 25%. Property sizes are all over 40,000 SF each, and the attached site plan demonstrates that there is enough space available to meet separation requirements for the wells and future septic systems. Proposed Lot 1 has a permitted well and septic system on it already with an alternate site specified. Proposed Lot 2 has a permitted septic system, but no alternate site shown. The location of the design test hole was specified in the original permit documents, however, and so an alternate site using the same design is shown within the test hole radius. Proposed Lot 3 has a permitted well but no septic system currently. The well pump will be pulled and the well capped. Test holes were dug on proposed Lot 3 in May of 2020 in areas 100' from any existing well. Monitoring tubes were placed in the test holes and groundwater checked over a week after the last hole was excavated. The test holes were dug down to 14'. Groundwater was not encountered. Soils were fairly uniform in the area, consisting mostly of silty sandy gravel (GM). Percolation benches were constructed between 4-5' below the ground surface in each test hole. The percolation cavity in each bench was prepared and presoaked in accordance with municipal requirements. One test resulted in 43.6 min/in, while the other perked at 6.7 min/in. Both test hole logs are attached. Using the slope and perk test information, an area appropriate for septic systems was designated for this lot. According to Table 7 of municipal code, perk rates between 25 and 60 minutes/inch require 16,000 SF of reserve area. All of the septic reserve area is on slopes under 25%. Additionally, we found well information for the four lots directly adjacent to the new subdivision to the east. Well depth was taken from the well logs where possible, while the most recent flow rate is given from COSA documentation in the Municipal on-site records. These are the closest wells to the properties and are representative of the wells that would be drilled on these lots. All wells are of very good yield and will easily support a single-family home. Property Legal Well depth (Ft) Flow rate (GPM) Finley, Lot 1 295 10 Finley, Lot 2 180 6 Finley, Lot 3 241 4.2 Finley, Lot 4 184 5.9 Proposed Millplace Estates, Lot 1 175 6.9 Proposed Millplace Estates, Lot 3 133+ 5+ It seems reasonable to conclude that the aquifer has the capacity to support new wells on the lots to the south. Any new wells will likely be around 200' deep and produce close to 5 GPM. All of the lots are sufficiently sized that a new well shouldn't have a significant effect on the existing wells. Finally, we researched nitrate levels of all properties within 250' of this proposed subdivision. The results are compiled on the following table. Property Legal Nitrate Levels, mg/L Date sampled T12N R3W SEC15, Lot 128 4.90 5/18/1995 9.65 8/17/2014 Finley, Lot 3 0.50 11/3/2004 0.10 8/21/1996 Finley, Lot 4 8.98 3/28/2013 Leach, Lot 3 1.80 1/12/2000 1.00 2/28/1995 Shell #2, Lot 3 0.60 8/30/1999 Proposed Millplace Estates, Lot 1 1.50 10/11/1993 Proposed Millplace Estates, Lot 3 8.50 8/15/2002 Based on our field studies, research, and water monitoring completed to date, it is clear that all lots of the proposed subdivision are capable of supporting new wells and onsite septic systems. Sincerely, Benjamin 'Schiller, PE MILLPLACE ESTATES, LOTS 1-3 T12N FL3Wl SEC 15 LL�O_T _12L — — — — — I — — — — — — LOT 130 1.�qT 131 NO OTHER WELLS WITHIN 25_0'_5FPR_0Pff_RTY E 104TH_AVE\'\, Ek/lSTING WELLS,;, Z L 0 SITE T\ ALTERNATE ILI" —(PER PERMIT) EXISTING \�ELL IA EXISTING4-13DRM SEPTIC SYSTEM M Lu "', .41 rr, n LL 0 I., ' --,- J -, 1\ LOT 1 CD u') ry /! 1 —30- BUILDING SET6 lK z 0 z 1Lli1..I_(73-591) /FIN SOB ry LOT 2` CIO iLOT 21 __j w PROPOSED WELL W I i co 0 4') co 1 II V SHAFER TH 8/20/90 4, ALTERNATE ITE: LOT 3 MATCH EXISTING DESIGN 50'x Sx 8' EFFECTIVE TRENCH 3Q00 1U UTILITY EASEMEN TI— 7 IV (73-59� EXISTING 3-BDRM SFPTIC SY TEM LOT 3 EXISTING VELL 10, UTILITY�EASEMEN (73-59) 10' T&1= EASEMENT,',; /lH 141, RG 940),, 7,15',T&E,�ASEMENT/ --(2008�:002330- 00 LOT 4 'SEPTICRESERVE AREA— J SHELL 02 SUB LEAQ SUB EXISTING SHARED \A ELL LOT _j (LOCATED ON LOT 2) Lij Lu Jifff� "I 1 co > LOT 2 LOT iii vja in Schiller 0 100 200 CE 125902 Sep 11 2020 EM �M ME FEET SLOPES > 25% 1"=100' SLOPES > 46% al" n I SOILS LOG AND PERCOLATION TEST E N G I N E E R I N G LEGAL DESCRIPTION: T 12N R3W SEC 15 L 16B (M I LPLACE EST. 1-3) PERFORMED FOR: PAUL KVERNPLASSEN DATE: 5/12/20 PROJECT No.: PARCEL ID#: 015-112-40 TECHNICIAN: M. JAKUBISIN DEPTH TEST HOLE 1 (feet) 1 2 3 4 6 7 8 9 10— 11 .� 12- 13 14 15 16 17 1 1 2 COMMENTS: SLOPE SANDY ORGANIC SILT MIXTURE GM SANDY SILTY GRAVEL WAS GROUND WATER ENCOUNTERED? NO If YES a WHAT DEPTH? - L DEPTH TO WATER AFTER MONITORING: NONE 0 DATE OF MONITORING: 5/22/20 P E DATE READING GROSS TIME (MINUTES) NET TIME (MINUTES) DEPTH TO WATER (INCHES) NET DROP (INCHES) 5/12 1 3:05 30 3 —0 / 7 -s 4 -s 2 3:38 30 3 0/ 7 -s 4 -% 3 4:11 30 3 -s/7 -s 4 8 PERCOLATION RATE: 6.7 (MIN/INCH) PERC. HOLE DIA. 6 (INCHES) TEST RUN BETWEEN: 4 FT. and 5 FT. DEPTH (feet) 1 - 2 J 4 5 6 7 8 9 10 11 12 13 1 1 1 17 18 19 20 SOILS LOG AND PERCOLATION TEST ENGINEERING LEGAL DESCRIPTION: T12N R3W SEC15 L16B (MILPLACE EST. 1-3) PERFORMED FOR: PAUL KVERNPLASSEN DATE: 5/12/20 PROJECT No.: PARCELID#: 015-112-40 TECHNICIAN: M. JAKUBISIN COMMENTS: TEST HOLE 2 1' OB SANDY ORGANIC SILT MIXTURE GM SANDY SILTY GRAVEL SLOPE WAS GROUND WATER ENCOUNTERED? NO S IF YES n WHAT DEPTH? - L DEPTH TO WATER AFTER MONITORING: NONE 0 DATE OF MONITORING: 5/22/20 P DATE READING GROSS TIME (MINUTES) NET TIME (MINUTES) DEPTH To WATER (INCHES) NET DROP (INCHES) 5/12 1 3:17 30 316/316 16 2 3:53 30 316/3 6 1ill 6 3 4:25 30 316 / 316 1ill 6 PERCOLATION RATE: 43.6 (MIN/INCH) PERC. HOLE DIA.--§ --fINCHES) TEST RUN BETWEEN: 4 FT. and 5 FT. 2 111=40' LOTS 16A & 16B SUBDIVISION LOT 16A 91,260 S.F. EAST 104TH AVENUE ®�S NJ rj OF.A4 4 Aqs,t� * : • 49TH ' *�� ffi •A ,f AG°stoldi u : LS7091 ••ajc Ar e'• /'/ p Cession°, 0 -41 NOTE: LIMITS OF A.C. PAVING AND PAVERS ARE SHOWN APPROXIMATELY DUE TO SNOW COVER AT THE TIME OF THIS SURVFY. A S- B U I LT J 21`J'Ob"YU"t lyU.SU' PROPERTY DEPICTED ABOVE AND THAT NO —_ J — — — — - -- — — — JEFF A. R.L S. IT IS THE RESPONSIBILITY OF THE OWNER TO 2000 E DOWLING RD., SUITE 8 — —— ANCHORAGE. ALASKA 99507 WHICH DO NOT APPS ON THE RECORDED SUBDIVISION PHONE 248-5454 10' UTILITY ESMT. GRID DATE HEREON BE USED FOR CONSTRUCTION OR FOR SW2536 ! ! I (73-59) ESTABLISHING BOUNDARY OR FENCE LINES, i 10' T. & E. ESMT. F.B. 2020-01 jos LI MILL16AD I I E ! (BK 141, PG 940) m 14 i it i I II IXISfiNG — R I i i t cnR24' I II i I I 1 129.3' I k ! "kO'Rc WELL i I i I I# I I I II I II I I I I I SNW I i I it I 11 I fl I Il PROPOSED NEW LOT LINE i I I I I !I I ?1 I II 30' BUILDING SETBACK I I I I I I I (73-59) 10' UTILITY ESMT. (73-59) I !• • 15' T. & E. ESMT. 1 I I 1 (2008-162329-0) i S 89°52'37'E 290.34' I ®�S NJ rj OF.A4 4 Aqs,t� * : • 49TH ' *�� ffi •A ,f AG°stoldi u : LS7091 ••ajc Ar e'• /'/ p Cession°, 0 -41 NOTE: LIMITS OF A.C. PAVING AND PAVERS ARE SHOWN APPROXIMATELY DUE TO SNOW COVER AT THE TIME OF THIS SURVFY. A S- B U I LT I HEREBY CERTIFY THAT I HAVE SURVEYED THE GASTALDI LAND PROPERTY DEPICTED ABOVE AND THAT NO SURVEYING, SURVEYING. LLC NGDI, ENCROACHMENTS EXIST EXCEPT AS INDICATED. JEFF A. R.L S. IT IS THE RESPONSIBILITY OF THE OWNER TO 2000 E DOWLING RD., SUITE 8 DETERMINE THE EXISTENCE OF ANY EASEMENTS, COVENANTS OR RESTRICTIONS ANCHORAGE. ALASKA 99507 WHICH DO NOT APPS ON THE RECORDED SUBDIVISION PHONE 248-5454 PLAT. UNDER NO CIRCUMSTANCES SHOULD ANY DATA GRID DATE HEREON BE USED FOR CONSTRUCTION OR FOR SW2536 4/7/2020 ESTABLISHING BOUNDARY OR FENCE LINES, ANCHORAGE RECORDING DISTRICT, ALASKA F.B. 2020-01 jos LI MILL16AD NOTE: NO CORNERS SET THIS DATE BUILDING DETAIL SCALE 1"=9n' 1 "=40' (cr O I3 ill 0 0 .r M 3 0 0 0 Z LOTS 16A & 16B SUBDIVISION LOT 16B 91,260 S.F. J 2f9"b2'37"E 290.34' II I !I I '8s. �•-- EXISTING I BUILDING I II i i II I I I i I Seanc SYSTEM i I II i II i I EI i I 61 I I !I 1 I II I I i PROPOSED NEW LOT UNE i I I ( { I I E SI T 3 { I I t I I I WELL I t I I I cor+�c ill t I I I II I E If I 30' BUILDING SETBACK I t I k (73-59) h ---i--',— 15' T. & E. ESMT. I t (2008-062330-0) I . 10' UTILITY ESMT. I i i I (73-59) I ----———————— — — — — —— UTILITY ESMT (73-59) ! I I S 89°48'45"E 289.89' AS -BU I LT I HEREBY CERTIFY THAT 1 HAVE SURVEYED THE GASTALDI LAND PROPERTY DEPICTED ABOVE AND THAT NO SURVEYING, LLC ENCROACHMENTS EXIST EXCEPT AS INDICATED. JEFF A GASTALDI, R.L.S.IT IS THE RESPONSIBILITY OF THE OWNER TO ZOOO E. DOWLING RD., SURE 8 DETERMINE THE EXISTENCE OF ANY EASEMENTS, COVENANTS OR RESTRICTIONS ANCHORAGE' ALASKA 89507 WHICH DO NOT APPEAR ON THE RECORDED SUBDIVISION PHONE 248-5454 PLAT. UNDER NO CIRCUMSTANCES SHOULD ANY DATA GRID DATE HEREON BE USED FOR CONSTRUCTION OR FOR SW2536 4/7/2020 ESTABLISHING BOUNDARY OR FENCE LINES. ANCHORAGE RECORDING DISTRICT, ALASKA F.B. 2020-01 JOB No. MILLI 6B NOTE: NO CORNERS SET THIS DATE F �4WP� AL ffi *; 491H ®........ �w . 0 ..� ®o : Jeffery A. Gostoldi N �O• LS -6091 �' '°� ffi a� 4/7/2020 • 4? ��® p'otessionol Lora