HomeMy WebLinkAboutCHICKABIRD ESTATES S12769Onsite File w D -,"4plb ESTATES 12769 A lcs Uan" GARNESS ENCITINEERTNI GROLJIP� Ltd,, ENGINEERING SALES CONSUCIIHIG, 3FA Jar4war-H-2, 2024 i 'T Municipality of Anchorage Development Service Department 1.4/jeilre'y Game . -7 On -Site Water & Wastewater Program _. 1 W Nz. 4 5i 4700 Elmore Road ;W. Anchorage, AK 99507 / b L/- Ref: Subdivision of Sun Valley North SID; Tract G-2 — (Proposed Chickabird Estates S/D; Lots 1 and 2) To whom it may concern: The owner of the referenced property is proposing to subdivide the 3.9 acres parcel into two (2) lots. The property currently has an existing 4-bedroom house, well, and advanced wastewater treatment system (AWWTS) located on it. The owner hired Timberline Surveying and Mapping to perform the work associated with subdividing the property and submitting it to the MOA Platting Department. Timberline provided us with a work sketch that shows the proposed lot line to subdivide the property into two (2) parcels (see attached). The owner has hired us to provide the supporting documentation to show that the proposed subdivision of the property meets sections 15.65,405 and 15.65.410 of the MOA Wastewater Ordinance. The following is the supporting documentation'. PROPOSED WELL AND SEPTIC RESERVE AREAS Per AMC 15.65.405, we are required to provide documentation to substantiate the capability of the propose lots to adequately dispose of wastewater showing that the proposed subdivision meets the requirements and standard of the MOA Wastewater Ordinance. Proposed Lot I is already served by an existing well and AVVVVTS. We have excavated and logged test holes for the purpose of subdividing the property (see attached soil logs). Based upon our investigation, only one area (labeled GEG TH#I), was found to be suitable to support an onsite septic system for proposed Lot 2. The percolation rate for GEG TH#1 was found to be 1.06 minutes/inch. Due to the limited area available for an onsite septic system, an A\AWFS will be required for subdivision purposes. Per AMC 15.65.410, "The lot must contain sufficient area to provide for a structure, and a well or water source, and sufficient area for an original onsite wastewater disposal system and one replacement subsurface disposal field designed in accordance with this chapter. The plat shag designate the maximum number of bedrooms allowed on each lot. The area to be used for disposal fields shall be designated on the plat for each lot as being unavailable for use for driveways, parking area, or structures." Since the 3701 Cast TudorRoad, Suite iOi 'Anchorage, Alaska 99507-1259 Phone: (907) 337-6179 ' Fax: (907) 338-3246 * Website: mm.garnessengineering.corn 00- 3 Q4 Poge 2 of 3 property will not support a conventional septic reserve area, we have designed a septic system that utilizes an AAMAIT.S. As can be seen on the attached site plan (page I of 4) and design drawing (page 2 of 4), we have shown a primary drainfield and reserve drainfield site utilizing an AWWTS. Attached is a detail drawing (page 3 of 4) of a Category 11 AWVvTS that can be used for this design. Attached is a detail drawing (page 4 of 4) showing a cross-section detail of the existing slope conditions (based upon topographical information provided by Timberline Surveying and Mapping) and a plan/profile detail of the proposed drainfield. Based upon this information, there appears to be sufficient area for a structure, driveway, well, and onsite wastewater disposal system for each lot. We are recommending the following notes be placed on the final plat: 1. A Categoryll orN advanced wastewater treatment system (AVWI1TS) approved by the Municipality of Anchorage is required for Lot 2. The structures on the lot shall have a combined total of no more than four (4) bedrooms. 2. Diveways, parking areas, and structures shall not be constructed over or downgradient of the wastewater disposal reserve areas. We have performed records research on some of the surrounding properties and have attached the well logs and other well information. The following is a summary of the well flow data including the most recent nitrate results for these properties: Sun Valley North; Tract G-2 (Proposed Lot 1) — Per the attached well log, the well was drilled on 5/1/2012 and is 190 feet deep. The well production at the time of drilling was 20 gpm A recent COSA was issued on this property with a well test performed on 7/19/2023 showing the well production was 4+ gpm. Water samples were also pulled for this COSA, and the nitrate results were 0.343 mg/L. Sun Valley North; Block 6, Lot 3 — Per the attached well log, the well was drilled on 8/12/2004 and is 175 feet deep. The well production at the time of drilling was 50 gpm, The last COSA issued on this property was in 2012 with a well test performed on 7/24/2012 showing the well production was 4.8 gpm. Water samples were also pulled for this COSA, and the nitrate results were 0.227 mg/L. Sun Valley North; Block 4, Lot 10 — Per the attached well log, the well was drilled 6/1992 and is 200 feet deep. The well production at the time of drilling was 4.5 gpm. The last COSA issued on this property was in 2012 with a well test performed on 1/12/2012 showing the well production was 3.61 gpm. Water samples were also pulled for this COSA, and the nitrate results were 1.01 mg/L. Sun Valley North; Block 4, Lot 9 — Per the attached well log, the well was drilled on 5/8/2003 and is 152 feet deep. The well production at the time of drilling was 4 gpm. The last COSA issued on this property was in 2013 with a well test performed on 8/1/2013 showing the well 3701 East Tudor Road, Suite 101 * Anchorage, Alaska 99507-1259 Phone: (907) 337-6179 * Fax: (907) 338-3246 * Website: www. garnessengineedng.corn Page 3 of 3 production was 3.4 gpm. Water samples were also pulled for this COSA, and the nitrate results were 0,802 mg/L. Sun Valley North; Block 5, Lot 4 — Per the attached well log, the well was drilled on 10124/2005 and is 237 feet deep. The well production at the time of drilling was 5 gpm. The last COSA issued on this property was in 2013 with a well test performed on 5/8/2013 showing the well production was 5+ gpm. Water samples were also pulled for this COSA, and the nitrate results were 0.736 mg/L. Based upon this information provided, it appears that water availability for drilling an additional well on proposed Lot 2 for this subdivision is good and the nitrate levels in the area of the proposed subdivision are not a concern. CONCLUSION: Based upon the information provided in this report, it is our opinion that the proposed subdivision of this property meets sections 15.65.405 and 1 5.65.41 0 of the MOA Wastewater Ordinance and that proposed Lot 2 will support an onsite wastewater disposal system (utilizing an AWWTS). Water availability is good, and that there are no concerns with nitrate levels in this area. If you have Wy questions, please contact us at 337-6179. Thank you for your assistance. A Ga(Hess, P.E., M.S. 3701 East Tudor Road, Suite 101 ' Anchorage, Alaska 99507-1259 Phone: (907) 337-6179 * Fax: (907) 338-3246 * Website: vmw. gamessengineering.com alA -2,11212-c,J 15$o DESIGN CRITERIA: DRAINFIELD DESIGN: '2 it it a NUMBER OF BEDROOMS: 4 (MAXIMUM) MAXIMUM DEPTH: 6-FEET �o s GALLONS PER DAY (GPD): 600 WIDTH:. 5-FEET PERCOLATION RATES: 1.06 LENGTH: 30-FEET rn PROPOSED APP. RATE: °4.0 GPDISQ.FT. M.O.A. APPROVED SAND FILTER: 2-FEET MINIMUM DRAINFIELD SO.FT.: 150 EFFECTIVE: 0.50 `UTILIZING A CAT II AWWTS ACTUAL SQ.FT.: 150 SEE CROSS - SECTIONAL DRAWING, SEE PAGE 4OF4 GEG TH1i1 co (2023) .-1610 RESERVE - —PROPOSED LD DRAINFIELD, DRAINFIE SITE SEE DESIGN CRITERIA AND PAGE 4 OF 4 C© PROPOSED AtMNTS �hN� SYSTEM, SEE PAGE 3 , y ,- 13-, —GEG TH-92 OF 4 FOR DETAILS. 2023 ( ) .� IN �hti SCALE: PROPOSED POSSIBLE —� LOT 2 4 EDROOM ®.o 1 = 40' `, `. (SEE NOTE) HOUSE oG LOCATION J /o OSSll9( FQ �LOTLOINED h - 1 � L IVA —POSSIBLE PROPOSED AREA FOR 0 "SOT L HOUSE WELL RADIUS g LOCATION '100' SEPTIC & BUILDING PROPOSED PLATTED SETBACK 50-FEET (SEE NOTE) AVVINTS WELL - RADIUS i nT WASTEWATER r 7HE AD` SST Elm 'ra R TREATMENT TMENT SYSTEM (,,AWWT ) TO BE PERMITTED AND INSTALLED. r HE 100-FOOT PLATTED SEPTIC & BUILIDNG `• SETBACK IS REQUIRED TO BE REMOVED FROM PLAT OR REDUCED TO 50-FEET J� "THROUGH THE SUBDIVISION PROCESS. Tt'i ' ) MAXIMUM NUMBER OF BEDROOMS FOR Tr E J --,- - •- ) PROPERTIES IN THE NEW SUBDIVISION. LIMITED TO d-BEDROOMS. J , PROPOSED .. �''`PROPOSED LOT LINE J LOT I Aw td T'F S •.......... v ... I ClFi " G SALES NG PREPARED FOR PHONE NUMBER PAGE NUMBER: 0 `Jaffrey A. Garness r �tl EGE-79 3 Z Al PROJECT/LEGAL DESCRIPTION _ DRAWN BY: TYPE OF WORK w DATE: ESS� g. LICENSE ���ikak #AECC884 GARNESS ENGINEERING GROUP, Ltd ENGINEERING SALES CONSULTING 3701 E. TUDOR ROAD, SUITE 101 'ANCHORAGF- ALASKA - PRONE (907)337-6179-WEMITE:www.gameueng0eeang.com ISOIL LOG - PERCOLATION TES LEGAL DESCRIPTION: SUN VALLEY NORTH; TRACT G-2 PERFORMED FOR: BEN AND ELYSE APPLEGATE DATE: 9/8/2023 DEPTH (fool) TEST HOLE #1 2- 3- 4- 5- 6- 7- 8- 9—i 10 11 1 SOIL CLASSIFICATIONS GW ORG GP ML GM G CNNII OL N!/1CL SWflllll111MH SP CH SM OH sc 12 - B. 0 13 — 14 — 15 — 16 — 17 — 18 --1 SM W/ ML TO GM W/ ML W/ COBBLES & BOULDERS DEPTH TO GROUNDWATER DATE DRY 9/812023 DRY 9/1212023 DRY 9/15/2023 DRY 1002023 SITE DATE READING NET TIME WATER LEVEL READING (INCHES) NET DROP (INCHES) 911212023 6- 1 2 —5 0 - 0/16' 6 - 0/16" 3 6- 4 6 0 - 0/16" 6 - 0116" 5 6- 6 6:10 0-0/16" 6 - 0116' 7 6" 8 6:20 0 - 0/16" 6 - 0/16' 9 6- 10 6:20 0 - 0/16" 6 - 0116" 11 6- 12 6:20 0-0116" 6 - 0116' 19 PERCOLATION RATE 1.06 (MIN./INCH) PERC. HOLE DIA, 6 (INCHES) TEST RUN BETWEEN 4.0 FT. AND 5.0 FT. 20 A FOUR HOUR PRESOAK WAS PERFORMED: E-1 YES 10 NO SOILS LOGGED BY: JODYMAUS PERCOLATION TEST PERFORMED BY. JODY MAUS COMMENTS: PERFORMED BY GEG, Ltd, 1, JEFFREY A. GARNESS, CERTIFY THAT THIS WAS PERFORMED IN ACCORDANCE I / WITH ALLSTATE AND MUNICIPAL GUIDELINES IN EFFECT ON THIS DATE- fl I II,, '11sr-9 "qt3j2'j- .v 141a, A$ _vA==am41 GARNESS ENGINEERING GROUP9 Ltd ENGINEERING SALES CONSULTING 3701 E. TUDOR ROAD, SUITE 101 'ANCHOMGE, ALASKA -PHONE (907) ISOIL L55 - PERCOLATION TEST LEGAL DESCRIPTION: SUN VALLEY NORTH: TRACT G-2 PERFORMED FOR: BEN AND ELYSE APPLEGATE DATE: 9/8/2023 DEPTH (feet) ITEST HOLE #2j PEAT SOIL CLASSIFICATIONS GW O. GP ML imilwl GM CL G C OL sw MH sp CH sm OH SC 7— GM W/ CLAY AND/OR SILT LENSES 9— .10- 12 — 13 — B.O.H. 14 — 15- 16 — 17- 18 —4 DEPTH TO GROUNDWATER DATE WET @ 11' 91812023 7' 9/12(2023 1 9.7' 9115/'2023 1 1 7.5' 10/212023 1 0 cj DATE READING NET TIME WATER LEVEL NET DROP READING (INCHES) (INCHES) 9112/2023, 9/15/2023, & 101212023 - BENCH EXCAVATED TO 3.5-4.0 FEET DEEP. WATER " 0 17N BENCH LIKELY DUE TO RAINFALL UNABLE TO PERFORM PERCOLATION TEST. 19 PERCOLATION RATE (MIN./INCH) PERC. HOLE DIA. TEST RUN BETWEEN FT. AND FT. 20 A FOUR HOUR PRESOAK WAS PERFORMED: F-1 YES IN NO SOILS LOGGED BY. JODYMAUS PERCOLATION TEST PERFORMED BY: N/A COMMENTS: PERFORMED BY GEG, Ltd. 1, JEFFREY A. GARNESS, CERTIFY THAT THIS WAS P�RFOtRMED IN ACCORDANCE WITH ALL STATE AND MUNICIPAL GUIDELINES IN EFFECT ON THIS DATE: it I'Li 12..3 6 (INCHES) 0