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Home My WebLink AboutCANYON VIEW ESTATES S12747CANYON VIEW ESTATES SUBDIVISION SEPTIC ANALYSIS & Hultquist Homes, INC. 12580 Old Seward Highway Anchorage, AK 99515 Prepared By: REV October 2023 Prepared By: Grant Mathews, P.E. * • t{ /TH W1W V}V. MWHIEVVS �'•• CE 135444 ,• AW Project Location The project site consists of an existing 3.5-acre parcel zoned R-10SL and identified as Tract 1, Block 1, of Canyon View Estates Subdivision. The parcel is located north of Canyon Road in Anchorage, Alaska. The site is accessed via De Armoun Road, to Upper De Armoun Road, to Canyon Road. Surrounding properties include a mix of undeveloped and developed residential single-family housing. Existing Conditions & Land Cover The site is currently undeveloped and well vegetated with mature trees and brush. Topographically, the site drains in a westerly direction. Roughly 60 feet of relief occurs from the southeast corner to the southwest. The average slope across the parcel is 10-15%. Proposed Development Plan The proposed development intends to subdivide and create two residential lots from the 3.5-acre parcel. Each lot will be served by individual wells and onsite septic systems as no public water or sewer infrastructure exists within the area. Lot 14 is 1.7 Acres and Lot 15 is 1.8 Acres. Access to each of the lots will be directly from Canyon Road. Existing grades are generally less than 25% across the site, and the proposed lot sizes exceed the 40,000 SF minimum lot size required to support onsite systems. Testing Process Triad Engineering, LLC performed septic testing onsite on August 30th, 2023. Weather conditions were generally cloudy and damp with temperatures in the mid-50's in the morning to mid-60's in the afternoon. Brownson Bros., LLC mobilized a 200 series excavator to the site and provided an operator for the geotechnical exploration. Test holes were staked by S4 Group in advance of testing. Access for the excavator was such that minimal to no clearing was required for testing. Each test hole was advanced to a depth of roughly 16 feet below ground surface (BGS). Upon completion of each test hole, a 4-in diameter perforated pipe was placed within the excavation and backfilled with the stockpiled soils. A bench was excavated adjacent to each test hole at an appropriate elevation so that percolation testing could be completed. A roughly eight -inch -deep hole was hand dug into undisturbed soils using a shovel and approximately two inches of 3/8" pea gravel was placed at the bottom of the hole. A four -inch diameter perforated PVC pipe was placed vertically into the test hole and the annulus backfilled with pea gravel. Water was then carefully poured into the pipe to a level approximately six inches above the bottom of the hole. Measurements were then taken using a standard tape measure. The process was repeated for each test hole as necessary to meet Title 15 requirements. The initial reading in all test holes exceeded %" drop, so pre-soaking was not required. The investigation proceeded from north to south, with Lot 15 being completed first and Lot 14 completed last. Free groundwater was not encountered during the investigation, but surficial weeps were encountered. Soils Soils encountered during the investigation were visually classified in general accordance with the Unified Soil Classification System (USCS). The general subsurface profile encountered for both Lots 14 and 15 consisted of approximately 12 inches of surficial organics followed by 15 feet of dense, silty gravel. Bedrock Bedrock was not encountered during the investigation and is not anticipated to negatively impact future development of the lots. Percolation Test Results Below is a summary of the percolation test results by lot and the subsequent reserve areas required. See the attached site plan for test hole locations on each lot. Table 1- Septic Testing Results Summary Lot Perc Rate Depth of TH Groundwater Groundwater Reserve Area (ft') (min/in) (Initial) Monitoring (Oct'23) Lot 14 <1 16' NGWE 10.5' BGS 10,000 Lot 15 <1 16' NGWE 10.5' BGS 10,000 Groundwater During the initial investigation, no groundwater was encountered. Subsurface flows were encountered as weeps in the sidewall of the excavation at approximately 10-ft BGS in TH-15A. The subsurface flows were deep enough that they did not affect the perc testing. It is unlikely that the water table would negatively impact future septic systems based on our field observations. Seasonal changes to the water table elevation are expected to occur due to rainfall and snow melt runoff. Groundwater monitoring in October 2023 found groundwater at 10.5-ft BGS in both test holes. Water Availability The MOA's COSA database was reviewed to assess water availability in the immediate vicinity of the proposed subdivision. The properties surrounding this parcel are largely undeveloped. However, the five closest properties with published data were found to have flow rates of 6-20 gpm. A summary of those rates are as follows: Parcel ID Drill date Well depth Static Water Level Production Nitrate Levels (mg/L) 021-021-36 10/12/22 206 ft 154 ft 6 gpm 1.61 021-021-48 11/11/22 206 ft 103 ft 20 gpm 2.93 042-081-03 4/12/05 225 ft 37 ft 4 gpm 4.08 042-081-IC) 10/21/93 106 ft 38 ft 6 gpm 3.16 042-081-16 8/28/80 140 ft 27 ft 6 gpm 2.27 Based on the available data, well production is not a concern for the proposed lots and no negative impacts to the well flows of adjacent properties is anticipated with the development of this subdivision. All nitrate readings in the immediate vicinity are less than 5 mg/L. Steep Slope Development A portion of the reserve area for Lot 15 is in an area with natural slopes ranging from 25%-30%. If a septic system is installed in this area, it will need to comply with 15.65.210.B.4. Steep slope disposal fields. Except as modified by this subsection, steep slope disposal fields shall comply with this chapter. a. General. A deep trench or non -mounded wide trench disposal field may be instaslled on a slope greater than 25 percent, but less than 46 percent, if it complies with all of the following conditions. Vertical separation distances below the disposal field shall be measured from the bottom of the droinrock at the up-grodient side of the disposal field. This condition can be met. ii. Trenches shall not exceed 60 inches in width. This condition can be met. iii. Natural vegetation within 50 feet down -gradient of the disposal field shall remain undisturbed, or the exposed slope shall be stabilized with erosion control vegetation or an approved equal prior to final operational approval. This condition can be met. The large lot size allows for natural vegetation to be retained, or the disturbed areas can be revegetated. iv. The distribution pipe invert shall be a minimum of 36 inches below the top of the natural organic surface, measured on the downhill side of the trench. (See chapter 15 for exceptions) This condition can be met. V. The disposol field shall be a minimum of 100 feet up -gradient from any slope exceeding 46 percent. (See chapter 15 for exceptions) This condition can be met. The slope on the property does not exceed 30% and all slopes downgradient of the lot within 100-ft are less than 30%. Conclusion In summary, perc test results indicate that both proposed lots contain soils capable of supporting on -site septic systems. Well -draining soils were encountered for both Lots 14 and 15. Groundwater was measured at 10.5-ft BGS during the month of October, when groundwater is typically at a seasonal high. Review of available well log information indicates that water is abundant in the area with an average production around 6 GPM. Thank you for your time and consideration in this matter. If you require additional information, please call 907-720-6128 or email me at grantmathews@triadak.com. Sincerely, Triad Engineering, LLC 7:1___ Grant Mathews, P.E. Attachments: Grading Plan Perc Test Results Municipality of Anchorage Development Services Department On -Site Water and Wastewater Section 47uoElmore St. po.Box 1esosuAnchorage, Anoyo1s-ssau Soils Log - Percolation Test Performed For: Cody Hultquist Date Performed: 8-30-2023 Legal Description: Canyon View Estates Lot 14 Block Township, Range, Section: NIA 0 5- 6- 7- 8- A- 10- 11- 12- 13- 14- 15- 1G- 17- 18- 1D- Surface Organics Silty Gravel (GM) Tan.Denoo 12'Cobbles Site Plan NONE MENEM MEMEMEMEME MEMEMEMEME MEMEMEMMM MMMMMMMMMM MMIEMMMMMMM MMMMMMMM MMMMMMMMMM MMMMMMMMMM MMMMMMMMMMI WAS GROUND WATER cwuouwrsnsor Yes o IFYES, xrWHAT DEPTH? L oq�mwate,After ----- " Date: 10-4-2023 | | xeamng | Date | umuo Time | Net Time | Depth mWater | Net Drop | PERCOLATION RATE ^1 �mm�x�m penoxo�somwsrcn 8^ TEST RUN BETWEEN 3.5 pr xwo 4.5 rr COMMENTS Added u 2 gal of water in | that / All water absorbed in les� that 5 min, Repeated 2x ------ PERFORMED BY: Triad Engineering, LLC | -Grant Mathews, P.E.CERTIFY THAT THIS WAS PERFORMED IN ACCORDANCE WITH ALL STATE AND MUNICIPAL GUIDELINES IN EFFECT ON THIS DATE. DATE: 10-4-2023 Municipality of Anchorage Development Services Department On -Site Water and Wastewater Section 4700 Elmore St. P.O. Box 196650 Anchorage, AK 99519-6650 www.muni.org/onsite (907)343-7904 Soils Log - Percolation Test * 4)1 TH • • ��GRAN� W. PotATNEWS Performed For: Cody Hultquist Date Performed: 8-30-2023 Legal Description: Canyon View Estates Lot 15, Block 1 Township, Range, Section: N/A 1- 2- 3- 4- 5- 6- 7- 10- 11- 12- 13- 14- 15- 16- 17- 18- 19- 20- Silty Gravel (GM) Tan, Dense 12" Cobbles WAS GROUND WATER ENCOUNTERED? No S Weeps @ 10' IF YES, AT WHAT DEPTH? L Depth to Water After 0 Monitoring? 10.5' BGS E Date: 10-4-2023 BOH @ 16' (NGWE) Site Plan ■■■■■■■■■■ ■®�. EEMEME ■■■■■■■■■■ ■■■■■■■■■■ ■■■■■■■■.■ ■■■■■■■■■■ ■■■■■■■■■■ ■■■■■■■■■■ ■■■■■■■■■■ Reading Date Gross Time Net Time Depth to Water I Net Drop PERCOLATION RATE <1 (minutes/inch) PERC HOLE DIAMETER 6" TEST RUN BETWEEN 4 FT AND 5 FT COMMENTS Added approx. 2 gal of water in less that 2 min. Ail water absorbed in less that 6 min. Repeated 2x PERFORMED BY: Triad Engineering, LLC I Grant Mathews, P.E. CERTIFY THAT THIS TEST WAS PERFORMED IN ACCORDANCE WITH ALL STATE AND MUNICIPAL GUIDELINES IN EFFECT ON THIS DATE. DATE: 10-4-2023 12 v —.t hI� U oo 7 10' T&E ESM T 25%-30 A 0 13 TH15A SEPTIC 0 PC T z z RESERVE AREA Pur 10,000SF I w 2016-073102-0 CF FF ELEV RECORD DRAVANG 1265 �27 t DATA PROVIDED BY, FF ELEV 1240 1250 that o on .... d mn his t.O=Ufy TWO ore a true and cocura e r,pnee"totio, of the P"*t SST ic 0 AP RESERVE AREA 7 15 CONTRACTOR: O,OOOSF 14 BY., A PC F2?,I33 TllLE!_DAl[: 2. DATA TRANSFERRED PUE v 2016-0I304 BY: COMPANY, GRADING NOTESVia° I DATA TRANSFER CHECKED Based an P111.6k nold ob- BLDG E ln�r i% y 1. ALL FILL SHALL BE PLACED IN ONE FOOT LIFTS, MAXIMUM, AND COMPACTED SETBACKS di,�,d..lh' he, direct oup-ison), the TO 95% MINIMUM AND IN COMPLIANCE WITH THE SOILS ENGINEER'S Contr-tor-pro,ided data RECOMMENDATIONS. NO ROCK OR SIMILAR IRREDUCIBLE MATERIAL WITH A appears to mpressnt the MAXMUM DIMENSION GREATER THAT 12 INCHES SHALL BE BURIED OR PLACED ".ject .. con.tted. IN FILLS. F, % ly-, 2. PRIOR TO PLACING FILL MATERIAL, THE GROUND SURFACE SHALL BE COMPANY PREPARED TO RECEIVE FILL BY REMOVING VEGETATION. SCARIFY THE EXISTING Il WELL GROUND SURFACE TO PROVIDE A BOND WITH THE PROPOSED FILL, ORGANIC RADIUS SOILS MAY BE SPREAD OVER FINISHED SLOPES AND PROPOSED LOTS AT A 1ITLE: 1AIL BY. MAXIMUM THICKNESS OF 6 INCHES. 3. PER AMCR 23.105.111.3, THE TOE OF FILL SLOPES SHALL BE MADE NOT NEARER TO THE SITE BOUNDARY LINE THAN ONE-HALF THE HEIGHT OF THE SLOPE WITH A MINIMUM OF TWO (2) FEET AND A MAXIMUM OF TWENTY (20) 20' T&C ESUT FEET. 4. PER AMCR 23,105,111.2, THE TOP OF CUT SLOPES SHALL NOT BE MADE NEARER TO A SITE BOUNDARY LINE THAN ONE -FIFTH OF THE VERTICAL HEIGHT OF CUT WITH A MINIMUM OF TWO (2) FEET AND A MAXIMUM OF TEN z 1) FEET. THE SETBACK MAY NEED TO BE INCREASED FOR ANY REQUIRED 0 INTERCEPTOR DRAINS. V) _j 5. FILL SLOPES SHALL NOT BE CONSTRUCTED ON NATURAL SLOPES STEEPER LLI DO THAN 1 UNIT VERTICAL IN 2 UNITS HORIZONTAL (50% SLOPE). WHERE SLOPES ARE STEEPER THAN 1 UNIT VERTICAL IN 5 UNITS HORIZONTAL (20% SLOPE) AND THE FILL HEIGHT IS GREATER THAN 5 FEET, A BENCH UNDER �Lj 'U2 6. HOURS OF THE TOE OF OPERATION THE FILL SHAVOLLLL BE BE BETWEEN 6:00 A.M.A.M� TO INSTALLED AT LEAST 1010:00 FEETP.MWIDE. > Z ., A MON.-SAT. ANY WORK SCHEDULED TO OCCUR OUTSIDE THESE HOURS OF 20' W ESWT A Z < OPERATION WILL REQUIRE A NOISE PERMIT PER AMC 15.07.070. 0 7. FILL CUT SLOPES TO BE 2:1 MAX. >- f2 0 8. THE CONTRACTOR SHALL MAINTAIN OPEN AND UNOBSTRUCTED ROUTES DAILY z UNTIL CONSTRUCTION IS COMPLETE. 0 < 9. NO FILL MATERIAL WILL BE PLACED IF FROZEN AND NO FILL SHALL BE 0 PLACED ON FROZEN MATERIAL. 10. A RIGHT OF WAY PERMIT IS REQUIRED FOR ANY WORK WITHIN THE MOA RIGHTS OF WAY. 11. MAINTAIN POSITIVE DRAINAGE PATTERNS AWAY FROM THE BUILDINGS. 12. AFTER GRADING IS COMPLETED, STABILIZE ALL DISTURBED AREAS. 10 11 FINISH FLOOR ELEVATIONS REFLECT AN APPROPRIATE RANGE OF ELEVATIONS NEEDED TO PROVIDE MODERATE DRIVEWAY GRADES AND MODERATE BUILDING SITE CUT OR FILL. THE FINISH FLOOR ELEVATION MAY VARY DUE TO THE SLOPING TOPOGRAPHY OF THE SITE AND THE LAYOUT/PLACEMENT OF THE HOUSE ON THE LOT, PUE 14. DRIVEWAYS ARE NOT TO EXCEED A 10% GRADE WITH A MINIMUM 10' LANDING 20t6-01JI02-0 CL OF NOT MORE THAN 2% WHERE THE DRIVEWAY INTERSECTS THE ROADWAY. z 0 Ln GRAPHIC SCALE �i a: 50 0 25 50 IDO 200 IN FEET I INCH =y FT. uu 100