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Home My WebLink AboutOWTS Design Reportô\l estWater En g i neeri ng ë consuttin g Engineers & Scientisìs 2516 FORESIGHT CtR(tE, #r GßAND JUNCTION, COLORADO 8T 505 Address TBD ltighway 13 Onsite lilastewater Treatment System DesÍgn 3-BR Single-Family Residence February 2021 Prepared for: Cruz R. Holguin Address TBD Highway l3 Rifle, C0 81650 Proposed Single-Family Residence Address TBD Rifle, CO 81650 Parcel No. 2129-232-00-07 4 Prepared by: WestV/ater Engineering Dean Goebel 2516 Foresight Circle #l Grand Junction, CO 81505 197 0, 241 -7 07 6 - F N 19? 0l 241 "7 097 1.0 Site Conditions The new onsitç wastewater treatment systen (O\VTS) will serve a proposed 3-BR single-family residenee oü a 40.âore parcel located apprcximately 6 miles north of Rifle, Colorado immediately adjacenf to Highway 13 (Figure 1). The OVfTS leachfîeld will use a total of 75 Quíck4@ Plus Standard Infiltrator units configured in five (5) trenches separated by four feet (side-wall to side-wall) of undisturbed soil with each trench using fifteen {15) Q4 chamber units for a minimum 31' x 60' firotprint and total disturbed area of approximately 31' x 63' with chamber end caps (Figure 2). Proposed soil treatment area (STA)/leachfield is southwest of proposed 3-BR dwelling in an area sloping approximatdy 8-10% to the west-southwest. Soils and percolation data were collected February 9,2021by WestWater Engineering in accordance with Garfield County On-site Wastewater Treatment System (OIVTS) Regulations (Regulations) adopted June 18, 2018, Logged soil profile shows the upper 0-0.9 feet is clayey sand loam overlying clayey sand interbedded witlt thin lenses of sandy clay from 0.9 down to 8.0 feet maximum depth of excavation (,A.ppendix A), Groundwater was not encountered in the 8- foot soils observation pit. Depth to high seasonal groundwater is estimated to be greater than 8.0 feet below ground surface. Percolation rates in the clayey sand with sandy clay lenses range frorn 20 to 50 minutes per inch (min/in) for respective percolation test holes cornpleted at varying depths from surface to 5.0 ftet. The åverage percolation rate for all 5 test holes completed in the clayey sand with sandy elay lenses is 33 nrinlin. Based on the Regulations, site soils are classifìed as Soil Type 3. Soil characteristics used to cletermine the long-term acceptance rate (LTAR) includes clayey sand to sandy clay texture, granular struoture, and percolation rates faster than the 4l-6t min/in range. The LTAR used to design the OWTS (Table l0- I Rcgulations) is û.35 gallons per day per square foot area lgpd/ft?). 2. 0 Wpstevsslts[-[þrvs åyelase Flow Maximum Ðaily Wastewater Flow (gpd): 3 bedroom roorn single-family dwelling 3 x 15û gpdlbedroorn = 450 grd $çptic Tarù Septic tank capacity for a 3-BR dwelling in Garfield County is 1,000 gallons {Table 9- I ilegulaiions). Far the 3*ËR dwelling use a two-ccmpartment 1,000 gallon n:inimum septic tank zipproved for use in G¿rrfield County in accordance witli the Regulations. 2 3.0 OrtrTS Dssisr T1re clayey sand with sandy clay lenses occurring at the 2.0 to 4.0 feet depth interval will be used for upper infiltrative surface for proposed STA (Figure 3). The maximum 4.0-foot soil depfh will promote optirnal secondary effluenttreatment using oxygen, bacteria and fungi processes. Trench excavation will removeapproximately 2.0 to 4.0 feet of soil and upperroot mass to prepare level surface for installing infiltrators on receiving soil surface providing secondary treatment of discharged septic tank effluent. The base elevation of STA is approximately 5,818 feet MSL. Soil should not be wet at time of excavation. Clayey sand used to cover STA rnust be slightly crowned overproposed trenches or match existing glade so water runs off, and is not ponded over any arca of STA/leachfield. Prior to backfilling finalsoil cover, a pervious barrier of woven geotextile fabric or similar peivious material shall be installed over the STA to prohibit soil intrusion. All setback distances in accr:rdance with the Regulations are applicable to septic systein instaliation. The-septic tank must be at least 5 feet, and STA at least 20 feet from plumbed structure(s) with basement, crawl space or footing drains and l0 feet if without basement, crawl space, or footing drains. STA's must be outside any easements and at least 10 tbet from property lines. Setback distances also apply to natural and artificial waterways, including a 50-foot setback from STA/leachfield To creeks, open irrigation ditches, and ponds" Setback froin the proposed potable water cistern serving the 3-BR dwetrling is l0û feet for the leachtield (25 feet with Colorado Division of Water Resources variance) and 50 feet for the septic tank. The cistern will bc located on the north side of proposed 3-BR dwelling thus capable of meeting these minimum setbacks without seeking a variance. Potable water lines must be at least 25 feet fro¡n any STA/leachfield. Dosignated leachfield repair area must be retained per Regulations as idle land set aside for future use onre primary field fails and no longer accepts wastewater, The new 1,0ûû gallon septic tank is the minimum volume allowed for a 3-BR dwelling prcviding at least 48 hours detention time {2 days x 45û gpd daily flow = 900 gallons) for influent wastewatsr flow from proposed 3-BR dwelling. Internal septic tank inlet and outlet tees must be installed per Regulations. An optional effluent filter may be installed instead of tee on the septic tank outlet. lf nsed, install the Orenco Systems Biotube Effluent Filter OSI Model FTW0444-36. Effluent {ilters typically require cleaning and maintenançe every 6 months. The following design calculations propose to discharge septic tank effluent to five {5) infiltrator trenches each with fifteen (15) Quick 4 units for a total disturbed area of approxirtately 31 fbet by 63 fbet. A total of 75 Quick 4 Standard Plus Infiltrator unils will be installed in lìve trenches generally orienterl rvest-northwest to east-southeast along topr:graphic çontours. 3 Soil Absorption Area Calcqlations Absorption Area {A) = Design Flow (Q)/LTAR Field percolation rate (t): 20 to 5û min/in Absorption field Area: ¿ = QILTAR, Where: A = Leachfield/Drainfield area square feet Q: Design Flodmaximum daily wastewater flow * maximum daily wastewater flow for 3-BR dwelling * 3 x 150 gpd/bedroom : 450 (gpd) LTAR = Loûg Term Acceptance Rate (max. hydraulic loading rate). * 0.35 gallons per dzy/ft2 A:450 gpdlO.3Sgpd/ftz * 1,285.7 N Quj-c. k4 Trençh Confi gur¿tigi : 1,285.7 ft? x 1.û (application method adjusünentr) x 0.7 (distrib. mcdia adjustment2) : 900 ft2; 900 ftz ,12 fr?:75 Q4 units; Use ?5 units. I Regulations Table 1A-2 size adjustment factor for Methods of Application in STAs 2 Regulations Table 10-3 size adjustment factor for Types of Media in STAs Note: County and State approved bottorn charnber area for Quick 4 Plus Standard Infiltrator Unit : tZ ft2. The Quick 4 Infiltrator Trench System will use a total of seventy-five {75) units. The five (5) trenches will each have fifteen (15) Q4 charnber units. Wastewater flow into the propose<l five {5} trenches will be split evenly using a distribution box. Use the top pod of Infiltrator faceplate for all inflr¡ent piping. 4. 0 S )istent'lnstsllêl!¡Oil-Rqquirernent Minirnum setback requirements must be in accordance with tlre Regulaiions. All sewer pipe couplings rnust be completed with primed and glued or bel1 and spigot joints using 4-inch SDR 35 PVC pipe. Schedule 40 PVC 4-inch pipe with a minimum l-foot soil cover must be used if 4 pipe is installed in a ve,hicular traffic crossing, Drain-wasts-vent (DIVV) Schedule 40 PVC pipe is specified for crossings but may also be used instead of SDR 35 PVC pipe. Building selryer pipe rnust be set at a slope between %-inch and 7¿-inch per foot slope (1 to 2o/o), preferably using the t/o-inch per foot slope as recommended by'the International Plumbing Code {IPC) as administered by the County. Fittings should use sweep 90-degee curves or two (2) 45- degree elbows at all influent pipe turns. Fittings must be DWV for schedule 40 PVC pipe. Clean"auts (Z-way) are required between tlwelling and septic tank and beyond septic tank where pipe lergths exeeed 100 feet from septic tank to STA/leachfield. lnstaller must adlere to mininurn depth requirements for leachfield and ensr;re gravity drainage into all septic system components to avoid using a lift pump. System cornponents must be placed on native soils or re-stabilized soils in excavated areas. STÁ/leachfield must be excavated level to ensure prepared infiltrative sr¡rface is level along entire length of STA. Solid 4-inch pipe is used in the header network out of distrjbution box. 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 $vstemloËBectiag WestWater Engineering is responsible for inspecting OWTS to ensure construction conforms to design plan ancl meets all aspects of County Regulations to include: ¡ Inspect system prior to backfilling including piping and septic system components. r Complete as-built drawing of system. 6.0 Desien Limitations The OWTS design is based on site specifìc soil conditions and percolation data collected in vicinity ofproposed leachfìeld/drainfield and local experience of designing OWTS's in Colorado, The desigrr is only valid for proposed new OWTS serving the single-famiiy residence at referenced locaticn provided in this repoú. WestWater Bngineering assumÊs no liability for inaccurate infomation or conditions that vary from design assurnptions listed above. Notify WestWater Engineering and/or the Garfield County official immediately if actual site co¡rditions differ fron those assumed here in. 5 Please do not hesitate to contact us if you have any questions regardiug this report. Respectfull¡ l^, þ{ t .n !;o.-', j"Jn-Åt**' Dean Goebel, M.S., P.G. Hydrogeologist Reviewed By: Jeremy Gilliam, P.E. Project Engineer 6 APPENDIX A Soils and Percolation Data 7 ^\Nestê consultins Jilater Engineering Engineers & Scientists 2516 FORESICHTCIRCTS #I GRANDJUNCTION, COLORADO 81505 SOILS AND PERCOLATION REPqRT 197 ol 241 -7 07 6 * F AX 97 Ol 241 -7 097 Date: February 9,2021 Consultant: Dean Goebelo M.S., P.G. Hydrogeologist WestWater Engineerìng 2516 Foresight Circle #l Crand Junction, CO 81505 (e70)24t-7076 Clienf Cruz R. Holguin Address TBD Rifle, CO 81650 Land Parcel: Address TBÐ, Rifle, CO 81650 2t29-232-00-074 sprl-ji LoG Site soils were investigated to collect site-specific data on the 40-acre rnostly vacant lot developed with one unplumbed bam north of Rifle, Colorado abutting Highway 13. The parcel has not been assigned an address at this time by Garfield County. Soils and percolation testing was conducted to collect site specific soils data for a proposed single-farnily dwelling onsite wastewater treatment system (OV/TS). Percolation testing procedures were conducted in accordance with Garfield County On-Site Vy'astewater Treatment System Regulations (Regulations). The two Percolation Test Sites are located on either side of the existing 2-track access road. The test site east of the road is located approxirnately 125 feet north of the south property line, 915 feet west of the east property line, and 430 southeast of the west property line. The test site west of access road is approximately I l7 feet north of the south property line, 970 feet west of the east property line, and 380 feet southeast of the west property line (Figure Al). Site soils were described arrd percolation tested in both areas with the east soils observation pit in an area sloping approxirnately 7 o/o to the west-southwest and the west test pit in an area sloping approximately 8% to the west-southwest. Althougli both soils and percolation test sites exhibited similar soil types and percolation rates, the west site will be used as the soil treatment/leachfield A-1 area due to its larger area and greater distance,from an infermittent creek. The ereek is located approximately 30 to 40 feet east-southeast of the east percolation test site. The 8-foot wcst soils observation pit shows a soil pro$le comprised of clayey sand loam to sandy clay with sorne angular cobble to small bounder sized clasts. Groundwater wâs not observed in the 8-foot soils pit; high seasonal groundwater is estimated to be greater than 8.0 feet. The soils profile log is summarized below and in Table 1, Ðark yellowish brown (10YR 4/4) clayey sand loam with granular structure occurs from û-0.9 feet overlying dark yellowish brown (l ûYR 4/4\ clayey sand loam with lenses of sandy clay with granular structure from 0.9-8.0 feet maximum depth of excavatio¿. The high seasonal water tablc estimate of 8.0 feet is based on low antecedent soil moisture content and the lask of soil coloringlredoximorphic features indicative of prolonged soil saturation via gtoundwater. Table 1. Tfest Pit Soil Log Descrìption vf : very fine; f = fine; m: medium and; crs * coarse for sand sized particles Percolation rates surnmanzed in Table 2 range from 20 to 50 minutes per inch (min/in). The averagepercolation rate for all five test holes is 33 min/in. Based on percolation data, macroscopic tactile soil analysis and estimated depth of the high seasonal water table, the infiltrative surfâce of the soil treatment arca{STA) ileachfield cân Õccur along a soil depth interval ranging from 2.0 to 4.0 feet depth. Site soils are categorized as Type 3 Soils based on sandy clay loam to clayey sand textures, granular structure, and more restrictive percolation rates within the 4l-ı0 min/in percolation rate rânge. At the time of installing the OWTS, soils should not be excavated under wet conditions to avoid cornpaction and smearing leading to reduction in permeability. Depth Interval (ft)Soil Description 0-0.9 Dark yellowish brown (10YR 4l4j clayey sand (f-vf¡' loam; rnoderate OM; granular; wet upper 6"; $age and greasewood vegetation 0,9-8.0 Dark yellowish brown (1OYR 414) clayey sand (f-vf) loam with lenses of sandy (f-vf) clay; low OM; granular structure; dry A-2 ID Depth {ft) Time Final Drop (in) Percolation Rate {min/in) l0:12 (start) 10:27 10:57 l1:27 12:12 I 2.8-3,8 4.375'5.750'7.25"8.5'10.0*5.625 ,l 2 û.0-1.0 7.875"8"5"9.375*10.û"11.0"3.125 3B 2.0-3.0 5.0'5"75"6.625*7.25*8.5"3.5 34 4 4.0-5.0 4.25*5.75"7.5"9.0"1t.375*6,125 20 5 2.û-3.0 7,75"9.25"8.75"9.25"10.125':2.375 50 Table 2. West Pit Percolation Test Results A-3 FTGURES Highwoy 15 Address TBDFIGURE A5Nestl,l¡oterEngineering2516 Foresight Circle,Grond Junction, C0 81(e70) 241-7076#1505^=USE TOP PORTINFILTRATOR FACE PI-ATEPROPOSED 5 INFILTRATOR TRENCHESCOVER WITH WOVEN GEOTEXTILE FABRIC PRIOR BACKFILLINGCROWN BACKFILL OVEROWTS TRENCHESEXISTiNGUND SUR344'448'31.0'MAXIMUM DEPTH 4.0 FETTMINIMUM DEPTH 2.0 FEETInstollotion Notes:1) Follow Monufocturers Instructionwww.infiltrotorsystems.com2) Screw Pipe Top Port ChomberFoceplote3) Screw Foceplotes ond Units Together4) Instoll Monitoring PortsSCALE 1,':5,\7\v\7oOPØcoQØlnco>c93O=