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Home My WebLink AboutOWTS PlansProposed 3-BR Main Single-Family Dwelling & 2-BR Plumbed Shop Onsite Wastewater Treatment System Design 897 County Roa d 231 sitro co 81652 Parcel No. 2L79-041-00-184 Prepared for: Joaquin Bianco 897 CR 231 silr, co 81652 November 2422 Prepared By: ôNest Water En g i n eeri n g ê consulting Engineers & Scientisis 2516 FORESIGHT CtRCtÊ, #r GRAND JUNCTION, COLORADO 81 505 1970)241-7076 * FAX (970) 241-7097 I.O 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 avacanf 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 area sloping approximately lYo south. Soils and percolation data were collected by WestWater Engineering November 18, 2022in accordance with Garfield County On-Site Wastewater Treatment System (OWTS) Regulations (Regulations). Soil profile in vicinity of proposed STA shows yellowish red silty sand loam occurring from 0 to 0-1.0 feet overlying brown silty sand down to 8.5 feet maximum depth 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 (bgs). 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 (min/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 l0-1 of the Regulations based on sandy silt loam textures and percolation rates faster and within the 16-25 mirVin range. Long-term acceptance rate (LTAR) used to design the OWTS (Table 10-1 Regulations) is 0.80 gallons per day per square foot area (gpdfff). 2.O WASTEWATERFLOWS Average Flow Maximum Daily Wastewater Flow (gpd): 3-BR main dwelling + 2-BR Plumbed Shop 5 x 150 gpd/bedroom : 750 gpd Septic 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 Garfìeld County to serve both dwellings. Internal effluent fìlter screen must be installed on septic tank outlet and a tee for the inlet compartment per Regulations. Page 1 3.0 OWTS DESIGN Silty sand occurring at the 2.0 to 4.0 feet depth interval 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 fungi processes. Trench excavation will remove approximately 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 I -foot of final cover (10- 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/leachfïeld. 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 10 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 S0-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. Internal 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 flrlters 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 disturb ed 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. Soil Absorption Area Calculations Absorption Area (A) : Design Flow (Q)/LTAR Field percolation rate (t): 5-17 minlin Leachfield Area:A:QILTAR, Where: A: Leachfield area square feet Page 2 Q : Design Flodmaximum daily wastewater flow : max. daily wastewater flow from 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 gpdl0.80 gpdlf:2 :937 .5 ff ADS ARC 36 Trench Configuration: 937 .5 ft2 x 1.0 (appl. method adjustmentr) x 0.7 (distribution media adjustmentz): 656.25 ft2; 656.25 ft ll5 ft : 43.75 ARC 36 chamber units; Use 44 units. 1 Regulations Table l0-2 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: T5 f(. The Four-Trench System will use atotal of forty-four (\ chamber units. Each trench will have eleven (11) ARC 36 chamber units. Wastewater 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 -inch SDR 35 PVC pipe. Schedule 40 PVC 4-inch pipe with a minimum l-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 Vs-inch and t4-inch per foot slope (1 to 2Yo), preferably using theYq-inch 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 tums. Fittings must be DWV for Schedule 40 PVC pipe. Clean-outs (2-way) are required between dwelling and septic tank and beyond septic tank where 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 length 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 3-4 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: Inspect system prior to backfilling including piping and septic system components. Complete as-built drawing of system 6.0 DESIGN LINIITATIONS 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 OV/TS 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 andlor the Mesa County official immediately if actual site conditions differ from those assumed here in. Please do not hesitate to contact us ifyou have any questions regarding this report. Respectfully, -Ë{À- r Dean Goebel, M.S., P.G. Hydrogeologist Reviewed By Keith o o /0t,AL Page 4 APPENDIXA SOILS AND PERCOLATION DATA ô\Nest Water En g i neeri ng ê consulting Engineers & Scientists 25t6 FORESIGHT ClRCtE, #1 GRAND JUI'¡CTION, COLORADO 8t5O5 41. SOILS AND PERCOLATION REPORT Date: November 18,2022 (9701241-7076 - FAX (970) 241-7097 Consultant:Dean Goebel, M.S., P.G. Hydrogeologist West\Vater Engineering 2516 Foresight Circle #l Grand Junction, CO 81505 (e70) 241-7076 Client Joaquin Bianco 897 County Road 231 Silt, CO 81652 Land Parcel: 897 CR 231, Silt, CO 8T652 2179-041-00-184 42. SOILS LOG Site soils were ìnvestigated at the 8.)Z-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-Site Wastewater 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 area (STA/leachfield is located in the southwestern portion of the parcel in an area sloping approximately lYo 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.S-foot soils observation pit. The soils profile log is summarized below and in Table Al 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 irrigation 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 alQ srlty 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 41. Soil Log Description vf : very fine; f : fine, m : medium and; crs : coarse for sand sized particles Percolation rates summarized 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, macroscopicltactile 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 T6-25 min/in 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 (ft) Time Final Drop (in) Percolation Rate (min/in) 10:08 (start) 10:38 11:08 11:38 12:08 (end) 1 2.0-3.0 2.5"7.75"I 1.5"dry dry 9.0 7 )0.0-1.0 4.0"6.75"8.25"9.t5"rr.125"7.r25 r7 5 2.5-3.5 5.0"I 1.5"dry dry dry 6.5 5 4 4.0-5.0 5.5"1r.75"dry dry dry 6.25 5 5 3.0-4.0 7.0"11.875"dry dry dry 4.875 6 6 3.4-4.4 7.0"Tr.625"dry dry dry 4 625 7 A-2 APPENDIX B FIGURES 897 COUNTY ROAD 231 Ð(STING OTYË SITE PI.AN FIGURE A1 WestWoter Englneerlng 2516 Forcslght Clrcle, fl Grond Junctlon, CO El5O5 (s7o) 211-7076 fra EXISTING SHARED WATER SUPPLY WELL WELL & IRRIGAÏON EASEMENT AND PUMP HOUSE 3O-FOOT ACCESS & UTLITY EASEMENT SOILS AND PERCOLAÏON TEST SITE ïH6 TH4 'rHz STAKED LOCATONS OF PROPOSED 5-BR DWELLING AND PLUMBED SHOP SLOPE 1% SOUTH EXISÏNG PROPERTY L¡NE (8.02r ACRES) 1 0 SCALE: 1":150' 150 WestWoter Englneerlng 2516 Forcolght Clrcl6, fi Grond Junctlon, C0 E1505 (e7o) 241-7076 fra FIGURE A2 897 COUNTY ROAD 231 PROPOSED OWTS LAY-OT'T PROPOSED POTABLE WATER LINE CORRIDOR FROM WELL PROPOSED CISTERN NOTE: ADS ARC 36 TRENCHES 44 UNITS 4 TRENCHES 11 UNITS EACH PROPOSED POTABLE WA LINE CORRIDOR FROM CISÏERN _PROPOSED DRIVEWAY ACCESS SOILS AND PERCOLATION TEST S|TE (r\?) t:::.) 2-WAY CLEANour(s) NEW 1,500 GALLON SEPÏC TANK MINIMUM DWELLING SEÏBACK TO LEACHFIELD 20 FT 2-WAY CLEANOUT DISÏRIBUÏON BOX RISER AÏ GRADE COVER ADS ARC 36 TRENCHES WTH GEO. TEXTLE FABRIC LINE LEAçHFTELÐ _19_Ff_ 40200 0 1 REPAIR LEACHFIELD AREA 24' x 58' PLUMBED PROPOSED 3-BR SINGLE-FAMIL RESIDENCE SCALE ":4Q' FIGURE A5E97 COUNTY ROAD 251oïvrs cîoss sEcïol,llTestWoterEngineering2516 Forcsight C¡øc #1Èond Junctlon, CO 8150s(s7o) 2+1-7076ÐUSE TOP FACEPLATE PORTCO\ER INFILTRATORS WTH GEOTEXÏLE FABRICCROV',fl BACKFILLOVER TRENCHESEXISTINGlr)Ðl_4'4'+lr)qtMAXIMUM DEPTH 4.0 FEETMINIMUM DEPTH 2.0 FEETSCALE 1o=5'INSTALLATON NOTES:1) FOLLOW MANUFACruRERS INSTRUCTONwww. ¡n fil trotors¡ætems. com2) SCREW PrPE TOP PORT CHAMBER FACEPLATE5) SCREW FACEPLATES AND UNrrS TOGETHER4) TNSTALL MON|TORTNG PORTS END OF EACH TRENCHALL FOUR BED CORNERS\v\v>ôr- 2.J<t att