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Home My WebLink AboutOWTS DesignProposed 3-BR Main Single-Family Dwelling & 2.BR mbed Shop ?VvuW-A Onsite W astewater Treatment Syste Design )Uc^*+a (otqo,o6qer :dr'?ffi3 rv\^D 897 County RoadzSl sitt, co 81652 Parcel No. 2179-041 -00-184 Prepared for: Joaquin Bianco 897 CR 231 silr, co 81652 November 2022 Prepared By: f,\N estWate r E n g i neeri n g e consultlng Engineers a scientist 251 6 KIREsIGHT CIRCLE,'I GMI{D JUNCTrcil, COU)NADIO 8T 5O5 l970l241-7076 -- FAx (9701 24r-7097 1.0 OWTS SUMMERY The onsite wastewater treatment system (OWTS) will serve multiple dwellings including a proposed 3-BR main single-family residence and 2-BR living space plumbed shop on avacant 8.O2-acre parcel located at897 CR 231 Silt, Colorado (Figure A1). The new OWTS will use a common 1,500 gallon septic tank and a total of 44 ADS ARC 36@ Standard chamber units configured in four (4) trenches each comprised of eleven (11) ARC 36 units. The trenches must be separated by at least four feet of undisturbed soil for a minimum 24' x 58' total disturbed area with chamber endcaps (Figure A2). Soil treatment area (STA/leachfield is south of proposed main and plumbed shop residences in an atea sloping approximately lYo south. Soils and percolation data were collected by WestWater Engineering November 18, 2022in accordance with Garfield County On-Site Wastewater Treatnent System (OWTS) Regulations (Regulations). Soil profile in vicinity of proposed STA shows yellowish red silty sand loam occutring lrorn 0 to 0-1.0 feet overlying brown silty sand dowr to 8.5 feet maximum deptli of the excavation (Appendix A). Groundwater was not encountered in the 8,5-foot soils observation hole, Depth to high seasonal groundwater table is estimated to be greater than 8.5 feet below ground surface (bg$. Percolation rates for the 6 percolation test holes completed in the silty sand loam and silty sand range from 5 to 17 minutes per inch (mir/in). Average percolation rate for all 6 test holes is 8 min/in. Site soils are classified as Soil Type 1 in accordance with Table 10-1 of the Regulations based on sandy silt loam textures and percolation rates faster and within the 16-25 min/in range. Long-term acceptance rate (LTAR) used to design the OWTS (Table 10-1 Regulations) is 0.80 gallons per day per square tbot area (gpd/ft'). 2.0 WASTEWATERFLOWS Average Flow Maximum Daily Wastewater Flow (gpd): 3-BR main dwelling + 2-BR Plumbed Shop 5 x 150 gpd/bedroom : 750 gpd Seotic Tank Individual septic tank capacity required to serve the 3-BR main and 2-BR plumbed shop living space is a minimum volume of 1,500 gallon common septic tank per Table 9-1 Regulations. Use a 1,500 gallon, two-compartment septic tank approved for use in Garfield County to serve both dwellings. Intemal effluent filter screen must be installed on septic tank outlet and a tee for the inlet compartment per Rcgulations. Page I 3.0 OWTS DESIGN Silty sand occuning atthe2.0 to 4.0 feet depth intervai will be used for upper infiltrative surface for proposed STA (Figure A3). High seasonal groundwater table is estimated to be > 8,5 feet, maximum depth of STA/leachfield shall not exceed 4 feet in accordance with the Regulations, The maximum 4.O-foot soil depth promotes optimal secondary effluent treatment using oxygen, bacteria and f'ungi processes. Trench excavation will remove approxim ately 2.0 to 4.0 feet of soil and upper root mass to prepare a level surface for installing the chamber units in the five trenches. Soil should not be wet at time of excavation. A minimum 1-foot of final cover (1 0- inches per Regulations) using the silty sand and silty sand will be slightly crowned over proposed trenches or match existing grade so water runs off, and is not ponded over any area of STA/leachfield. Prior to backfilling, cover the trenches with non-woven geotextile fabric or similar permeable material to prohibit soil intrusion into the chamber louver vents, All setback distances in accordance with the Regulations are applicable to septic system installation. The septic tank must be at least 5 feet, and STA at least 20 feet from plumbed structure(s) with basement, crawl space, and or footing drains. STA's must be outside of any easements and at least l0 feet from property lines and 100 feet from existing shared water supply well located on the north abutting parcel. Setback distances also apply to natural and artificial waterways, including a 50-foot setback from STA/leachfield to open irrigation ditches and ponds. Potable water lines serving the residences must be 25 feet from the STA/leachfield. Designated leachfield repair area must be retained per Regulations as idle land set aside for future use once primary fields fail and no longer accepts wastewater. Proposed 1,500 gallon septic tank will be maintained to provide at least 48 hours detention time for received wastewater flow from the structures they serve. Intemal septic tank inlet and outlet tees must be installed per Regulations. An effluent filter must be installed instead of tee on the septic tank outlet, Use the Orenco Systems Biotube Effluent Filter OSI Model FTW0444-36 or equivalent. Effluent filters typically require cleaning and maintenance every 6 months. The following design calculations propose to discharge septic tank effluent to four (4) ARC 36 trenches each with eleven (1 1) chamber units in a disturbed area approximately 24 feet by 58 feet. This includes 4 feet of undisturbed soil separating the trenches. A total of 44 ADS ARC 36 Standard chamber units will be used in the trenches generally configured east to west. Soi I Absorpti on Afep C alaul4ji.ons Absorption Area (A) : Design Flow (Q)/LTAR Field percolation rate (t): 5'17 minlin Leachfield Area: A:QILTAR, Where: A: Leachfield area square feet PageZ Q : Design Flodmaximum daily wastewater flow : max. daily wastewater flow frorn 3-BR main and 2-BR Shop :5 x 150 gpd/bedroom:750 (gpd) LTAR: Long Term Acceptance Rate (max. hydraulic loading rate) :0.80 gallons per daylff A: 750 gpd/0.SO gpdlfll : %7.5 te ADS ARC 36 Trench Configuration: %7,5 ff x 1.0 (appl, method adjustmentl) x 0,7 (distribution media adjustment2)= 656.25 ft2; 656.25 fe l$ f( : 43.75 ARC 36 chamber units; Use 44 units. 1 Regulations Table lO-2 size adjustment factor for Methods of Application in STA 2 Regulations Table 10-3 size adjustment factor for Types of Media in STA Note: County and State approved bottom chamber area for ARC 36 Standard ADS Unit: l5 ft2. The Four-Trench System will use a total of forty-four @$ chamber units. Each trench will have eleven (11) ARC 36 chamber units. Wastewatff flow into the trenches will be equally distributed using a distribution box. 4.0 SYSTEMINSTALLATIONREOUIREMENT Minimum setback requirements must be in accordance with the Regulations. All sewer pipe couplings must be completed with primed and glued or bell and spigot joints using 4-inch SDR 35 PVC pipe. Schedule 40 PVC 4-inch pipe with a minimum 1'foot soil cover must be used if pipe is installed in a vehicular traffic crossing. Drain-waste-vent (DWV) rated Schedule 40 PVC pipe is specified for crossings but may also be used instead of SDR 35 PVC pipe. Building sewer pipe must be set at a slope between %-inch and Vs-rnch per foot slope (1 to 2Yo), preferably using the Vq-rnch per foot slope as recommended by the International Plumbing Code (IPC) administered by the County. Fittings should use sweep 9O-degee curves or two (2) 45- degree elbows at all influent pipe turns. Fittings must be DWV for Schedule 40 PVC pipe. Clean-outs (2-way) are required beh^ieen drvelling and septic tank and beyond septic tank v.,here pipe lengths exceed 100 feet from septic tank to STA/leachfield. Installer must adhere to minimum depth requirements for leachfield and ensure gravity drainage into all septic system components to avoid using a lift pump. System components must be placed on native soils or re-stabilized soils in excavated areas. Page 3 Infiltrator trenches must be excavated level to ensure prepared infiltrative surface is level along entire tength of STA. Solid 4-inch pipe is used in the header network of sanitary tees. The owner will ultimately be responsible for septic system maintenance including pumping septic tank once every 34 years and cleaning effluent filter every 6 months. 5.0 SYSTEM INSPECTION WestWater Engineering is responsible for inspecting OWTS to ensure construction conforms to design plan and meets all aspects of County Regulations to include: o In$pect system prior to backfilling including piping and septic system components. o Complete as-built drawing of system. 6.0 DESIGN LIIVIITATIONS The OWTS design is based on site specific soil investigation collected in vicinity of proposed leachfield and local experience of designing OWTS's in Garfield County, Colorado, The design is only valid for proposed new OWTS serving proposed residences at referenced location provided in this report. WestWater Engineering assumes no liability for inaccurate information or conditions that vary from design assumptions listed above. Notify WestWater Engineering and/ortheMesa County offrcial immediately if actral site conditions differ from those assumed here in. Please do not hesitate to contact us ifyou have any questions regarding this report. Respectfully, f\ IJ t ,ij l.*,lrr* . .i . r, r1' {rc{ Dean Goebel, M.S., P.G. Hydrogeologist Reviewed By: Keith /ot{AL Page 4 APPENDIXA SOILS AND PERCOLATION DATA fa\Nest Water En g i n ee ri n g e consulting Engineers & Scientiis 25ro FOES|GHTCnCLE, fi GRANDJUI{CTION, COTORADO 81505 AI. SOILS A}ID PERCOLATION REPORT Date: November 18,2022 (gtol 241-7076 - FAX l9t0l 24t-7097 Consultant:Dean Goebel, M.S., P.G. Hydrogeologist WestWater Engineering 2516 Foresight Circle #1 Grand Junction, CO 8 I 505 (e7o)241-7076 Client:Joaquin Bianco 897 County Road 231 Silt, CO 81652 Land Parcel: 897 CR 231, Silt, CO 81652 2119-A4t-O0-184 A2. SOILS LOG Site soils were investigated at the 8.02-acre vacant parcel to collect site specific design criteria for an onsite wastewater treatment system (OWTS) to serve a proposed 3-BR single-family dwelling and plumbed shop with 2-BR living space located at897 County Road, Silt, Colorado. Percolation testing and soil evaluation procedures were conducted in accordance with Garfield County On-SiteWastewater Treatment System (OWTS) Regulations (Regulations). The Percolation Test Site is located approximately 175 feet south of the north property line and 300 feet east of the west property line (Figure Al). The proposed OWTS soil treatment arsa (STA/leachfield is located in the southwestern portion of the parcel in an area sloping approximately l%o to the south. The excavated soils observation pit shows a uniform soil profile of silty sand loam topsoil overlying silty sand, Groundwater was not encountered in the 8.5-foot soils observation pit. The soils profile log is summarized below and in Table A1. Yellowish red (5YR 4/6) silty sand loam, disturbed from past cultivation from 0.0-1.0 feet, overlying silty sand from 1.0-8,5 feet maximum depth of excavation. Estimated high seasonal groundwater is estimated to be greater than 8.5 feet based on the timing near the end of the irigation season and the lack of soil moisture or signs of prolonged saturation in the bottom of soil observation pit. A-1 Depth Interval (ft)Soil Description 0-1.0 Yellowish red (5YR a/6) silty sand (vf)'loam Ap horizon disturbed by past cultivation; low-moderate organic matter (OM); blocky, dry; roots; sparse native grass vegetation 1.0-8.5 Strong brown (7.5YR 5/6) silty sand (vf); low OM; granular laminar structure; moderate OM; granular structure; roots; dry Table A1. Soil Log Description vf : very fine; f : fine; m : medium and; crs: coarse for sand sized particles Percolation rates summarrzed in Table A2 show a range from 5 to 17 minutes per inch (min/in) with an average of 8 min/in. Based on percolation data, macroscopic/tactile soil analysis and depth to the high seasonal water table at 8.5 feet, bottom of leachfield (top of infiltrative surface) should be no deeper than 4,0 feet per Regulations. Site soils are categorized as Type I soils based on silty sandy loam texture, granularJaminar soil structure and percolation rates mainly faster than the 16-25 minlin range. Soils should not be excavated under wet conditions to avoid compaction and smearing leading to reduction in permeability. Table A2. Percolation Test Results ID Depth (rt) Time Final Drop (in) Percolation Rate (min/in) l0:08 (start) 10:38 I 1:08 1 1:38 12:08 (end) I 2.0-3.4 2.5"7 75"I I.5"dry dry 9.0 7 2 0.0-1.0 4.0"6^75"8.25"9.75"tr.t25"7.t25 17 J 2.5-3.5 5.0"I 1.5"dry dry dry 6.5 5 4 40-50 5.5"11.75"dry dry dry 6.25 5 5 30-40 7.0"17.975"dry drv dry 4 875 6 6 3.4-4,4 7.0"Ir.625"dry dry dry 4 625 7 A-2 APPENDIX B FIGURES lVcstWotcr Englneorlng w 2516 Forcelght Clrclq, ,l Grond ftnctlm, C0 El5O5 (s7o) 211-7076 g FIGURE A1 897 COUNTY ROAD 231 D(STING OWIS SITE PI.AN EXISTING SHARED WATER SUPPLY TIUELL WELL & IRRIGATION EASEMENT AND PUMP HOUSE 5o-FOOT ACCESS & UTILITY EASEMENTt::_l SOILS AND PERCOLATION TEST SITE TH TH STAKED LOCA1IONS OF PROPOSED 5-BR DII/ELLING AND PLUMBED SHOP SLOPE 1% SOUTH EXIS]ING PROPERTY LrNE (8.02r ACRES)-.rl 1 SCALE:1":150' 150 lVestWoter ..,.-E:gr:il1?, 2516 Forcolghi Clrcl., fi kond Junctlon. C0 81505 (970) 241-707A e FIGURE A2 897 COUNTY ROAD 231 PROPOSED OWTS I.AY-OI,T PROPOSED POTABLE WATER LINE CORRIDOR FROM WELL PROPOSED CISTERN NOTE: ADS ARC 36 TRENCHES 44 UNITS 4 TRENCHES 11 UNITS EACH PROPOSED POTABLE WATER LINE CORRIDOR FROM CISTERN _PROPOSED DRIVEWAY ACCESS SOILS AND PERCOLATION TEST S|TE (r\?) 2-WAY CLEANoUT(S) NEW 1,500 GALLON SEPTIC TANK MINIMUM DITVELLING SETBACK TO LEACHFIELD 20 FT 2-rvAY CLEANOUT DISTRIBUTION BOX RISER AT GRADE COVER ADS ARC 36 TRENCHES WTH GEO- TEXNLE FABRIC fq LINE _qSLBA,CK_T9_ LEAqH fl E LD _19_F_T_ o LEACHFIELD AREA 24' x 56' PLUMBED PROPOSED 3-BR SINGLE_FAMIL RESIDENCE 40 SCALE: 1"=4O' 897 COUNTY ROAD 251 OWTS CRG SECltOtl RGURE A5Engineering 2516 Forcdsht Cndc #lfond &nctlon, CO E1505 (9701 211-7Ot6 Wcstt{otrg USE TOP FACEPLATE PORT CO\ER INflLAATORS WTH GEOTEXTILE FABRIC CROUdN BACKFILL O\ER TRENCHES EXISIlNG io ir) l_ 4'4,4' lr) at MAXIMUM DEPTH 4.0 FEET MINIMUM DEPTH 2.0 FEET !r SCALE l'=5' INSTALLATION NOTES: 1) FOU-OW MANUFACruRERS TNSTRUCTTON 2) 3) 4) www. infi I tro torslrstem s. com SCRETY PIPE TOP PORT CHAMBER FACEPLATE SCREV{ FACEPLATES AND UNITS TOGETHER INSTALL MONITORING PORTS END OF EACH IRENCH AtL FOUR BED CORNERS \7\F>6l-::Z+<(h ttt