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Home My WebLink AboutOWTS Design 02.10.2021ra\Nest Water E n g i n ee ri n g ê coisulting Engineers & scientis'ts $tAt{rËp 2516 FORESIGHT ClRCtE, #t GßAND ',UNCTION, COIOfiAÞO 81505 County Road 218 Address TBD Onsite Wastewater Treatment System Design 4-BR Single Family Residence February 2021 Prepared for: Marcelino Holguin County Road 218 Address TBD silt, co 81652 Proposed 4-BR Single-Family Residence County Road 218 Address TBD silt, co 81652 Parcel No. 2l 79-023-01 -003 Prepared by: WestWater Engineering Dean Goebel 2516 Foresight Circle #1 Grantl Junction, CO I1505 p7ar241"1076 * FAX (e7o) 241-7097 1,0 Site Conditioqs The onsite wastewater treatment system (OV/TS) will serve a proposed 4-BR single-family residence on a vacant 2"9-acre parcel located north of Silt, Colorado at CR 218 address TBD (FigureAl). The new OWTS will use atotal of 72 Quick4& Plus Standard Infiltrators configured in a single bed using four (4) rows each with eighteen ( l8) Q4 units for a minimum 12' x 751 footprint including chamber endcaps (Figure A2). Proposed soil treatment areas (STA)ileachfield are located west and north of proposed residçnce adjacent to the soils and percolation test sites" These proposed STA/leachfield sites are relatively flat lying areas (approximately 5,560 feet ele¡ation) on an upper bench where the house will be located. The west STA/leachfield site was chosen to meet the 1Oû-foot minimum setback to the water supply well proposed for the northern area of parcel. Soils and percolation data wers collected February 9,2021 by TVestV/ater Engineering iu accordance with Garfield County On-Site Wastewater Treatment Regulations (Reguiations). Soil profile in the north percolation test site shows 0-0.9 feet dark yellowish brown sand with silt overlying 0.9-8.0 feet of brownish yellow sand with thin clays sand lenses at maximum depth of excavation. The west test site shows a unifonn profile of alluvium with yellowish red sandy matrix supporting well-rounded pebble- to small bounder-sized clasts from the surface down to 8.0 feet. Groundwater wâs not encountered in either of the 8.0-foot soils observation pits. Based on hending antecedent sail moisture conditions with depth'and the laok of redoxirnorphic features indicative of prolonged saturation, estimated high seasonal water table is greater than 8.0 feet. Percolation testing results for test holes completed in the sand with silt and lenses of clayey sand range from 14 to 46 minutes per inch (min/in) and the alluvium 7 to 48 minlin {Appendix A). Based on soil texture, structure and percolation rates, site soils slated to be used as infiltrative surface {2- to 4.foot depth interval) for received rvastewater are classified as Soil Type 2 in accordance with the Regulations. Long-temr acceptance rate (LTAR) used to design the OWTS (Table l0-1 Regulations) is 0.60 gallons per day per square foot area (Wdl#). 2.0 V/astewater Flows Averaqe flow Maximum Daily Wastervater Flow (gpd): 4 bedroom roorn dwelling 4 x 150 gptl/betln.rom = 600 gpd Septic Tank Septic tank capacity (Table 9-1 Regqlations) requires a 1,25t gallon miniurum septic tank to serve proposed 4-BR dwelling. Septic tank capacity also comesponds with a 48-hour rletention tirne fur design wâstewater flolv (2 days x 600 gpd = 1,2AA gallons). The proposed 1,250 gallon septic tank meets these sizing requirements. 1 For 4-BR dwelling septic tank capacity must be > 1,250 gallons; use a two* compartment sepfic tank approved for use in Garfield County. 3.0 OWTS Desisn Sa¡d with silt or alluvium occurring at the 2.0 to 4.û-foot depth interval will be used for upper infilhative surface for proposed STA (Figure A3). The maximum 4.0-foot soil depth promotes optimal secondary effluent treatment using oxygen, bacteria and fungi processes. Bed excavation will remove any sparuo vegetation and root mass to prepare level su¡face f'or installing infiltrators on receiving soil surface providing secondary treahnent of discharged wastewater. Soil should not be wet at time of excavâtion. Sand with silt or alluvium (try to segregate out clasts larger than gravel size) used'to cover STA tnust be slightly crowned over proposed bed to pfomote water runoff and prohibitponding over aüy area of STAlleach{ield. Prior to backfilling, cover in{iltrator units with woven geotextile fabric or similar material to prohibit soil intrusion. All setback distances in accordance with the Regulations are applicable to septic system installation. The new 1,250 gallon septic tank rnust be at least 5 feet and STA 20 feet from the proposed residence. STA's must be outside any easements and at least l0 feet from property lines and at least 25 feet from potable water lines and furrow irrigation. The STAlleachfield, including proposed repair leacåfield âreas, must be at least 100 feet from proposed water supply well in the northeln portion of parcel and 50 feet Ílom surface water including the lake located in the nor"thwest parcel corner. The proposed new 1,250 gallon septic tank will provide at least 48 hours detention time for influent wastewater flow from the proposed 4'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 ths septic tank outlet. Use the Orenco Systems Biotube Effluent Filter OSI Model FTW0444- 36, Effluent filters typically require cleaning asd maintenance every 6 months. The following design calcu-lations propose to discharge septic tank effluent to one (1) Quick a Infiltrator Bed comprised of four {4) rows each with eighteen {18) units for a minimum disturbed ârea approximately 12 feetby 75 feet. A total of 72 Quick 4 Standard Plus Infilhator units will be installed in a single bed conüguration. $,-çil.Absorptiqn Area Calculations ,Absorptian Area {A) = Design Flow {Q)/LTAR Field percolation rate {t): 7 to 48 midin Absorption Field Area: 6: Q/LTAR, 2 Where: A: Drainfield area square feet Q = Design Flodmaximum daily wastewater Ílow = maximum daily wastewater flow of 4*BR dwelling * 4 x i50 gpdrbedroorn:600 {gpd) LTAR * Long Term Aceeptance Rate (max. hydraulic loading rate) = û.6û gallons per day/ftz A = 600 gpd/0.60 g¡rd/ft2 : 1,000 ft2 Ouich4 Bed Configuration: 1,000 ft2 x 1.2 (appl. method adjustmentl) x 0.7 {distribution media adjusfmentz) : 840 ft2; 840 ftz /12 ft7 :7t Q4 units; Use 72 units. I Regulations Table T0-2 size adjustrnent f¿ctor for Methods of Application il STA 2 Regulations Table 10-3 size adjustrnent factor for Types of Media in STA Note: County ând State approved bottom chamber area fo¡ Quick 4 Plus Standard hrfiltrator Unit * 12#. The one (1) Quick 4Infiltrator Bed will use a total of seventy-two (72) units, The bed will have four (4) rows each with eighteen (18) Q4 charnber units. V/astewater flow into the proposed single infiltrator bed system will equally split using a distribution box. 4.0 $ystem Itstallation Requirement Minimum sêtback requirements must be in accordance with the Regulations. All sewer pipe couplings must be completed withprimed and glued or bell and spigot joints using 4-inch SDR 35 PVC pipe. Schedçle 40 PVC 4-inch pipe with a minirnum 1-foat soil cover must be used if pipe is installed in a vehicular traffic crossing. Drain-waste-vent (DWV) Schedule 40 PVC pipe is specified f.or crossings but may also be used instead of SDR 35 PVC pipe. Building sewer pípe must bc set al a slope between %-inch and 7¿-inch per foot slope (1 to ZYo), preferably using the t/¿-inehpor foot slope as recommelded by the International Plurnbing Cocle (lPC) as adninistered by the County. Fittings should use sweep 90-degee curves or twc (2) 45- degree elbows at all influerrt pipe turns. Fittings must be DWV for Scl¡edule 4û PVC pipe, Clean-outs (2-way) are required between dwelling and septic tank and beyond septic tank where pipe lengths exceed i00 feet from septic tank to STA/leachfield. 3 Installer must adhere to minimum depth requirements for leachfield to ensure gravity flow into proposed infiltrator bed. OWTS components must be placed on native soils or re-stabilized soils ín excavated areas. STA/leachfield must be sxcavated level to ensure prepared infiltrative surface is level along entire length of STA. The owner will ultimately be responsible for septic system maintenance including pumping septic tank once every 3-4 years and cleaning effluent filter (if opted) every 6 months. 5. 0 Svste. _{n. Inspecti on WestWater Engineering is responsible for inspecting OV/TS to ensure construction confoms to design plan and meets all aspects of County Regulations to include: r Inspect system prior to backfilling including piping and septic system components. ¡ Complete as-built drawing of system. 6.0 Desien Limitations The OWTS design is based on site specific soil investigation collected in vicinity of proposed drainfield and local experience of designing O'WTS's in Colorado. The design is only valid for proposed new OV/TS serving the single-farnily residence at referenced location provided in this report. West'Water Engineering assumes no liability for inaccurate information or conditions that vary from design assumptions listed above. Notiff West'Water Engineering and/or the County regulatory official immediately if actual site conditions differ from those assumed herein. Please do not hesitate to contact us if you have any questions regarding this report. Respectfull¡ ;"'.. r"t ; ii | "..", "-tr."*c- Dean Goebel, M.S., P.G. Hydrogeologist Reviewed By: Jeremy Gilliam, P,E Project Engineer 4 APPËNDIX A Percolation Data 5 Q\N estlilater En g i neeri n g 4 Consulting Engineers & Scientists 251 6 FOßES|GHT CtRCtE, #1 GRAND JUNCT|ON, COLORADO 8l 505 SOILS AND PERCOLATION REPORT 197or241-7076* FAX (970) 241-7097 Date: Consultant: Client: Land Parcel: February 9,2021 Dean Goebel, M.S., P.G. Hydrogeologist WestWater Engineering 251ó Foresight Circle #l Grand Junction, CO 81505 (e70) 241-7076 Marcelino Holguin County Road 218 Address TBD silt, co 81652 Address TBD, Silt, CO 81652 2r79-0n-al-003 SOILS LOG Site soils were investigaled to collect site-specific data on the vacant Z.9-acre lot immediately no:1h of East Ballard Avenue, Silt, Colorado. The parcel has not been assignsd an address at this time by Gar{ield County. Soils and percolation testing was conducted to collect site specific soils data for a proposed single-farnily dwelling onsite wastewater treatment system (OWTS). Percolation testing procedures were conducted in açcordance with Garfield County On-Site Wastewater Treatment System Regulations (Regulations). The two Percolation Test Sites are located on fhe flat-lying bench north and west of proposed house site. The north soils and percolation site shows a uniform soil profìle cornprised of sand and west test site alluvium from surface down to 8.0 feet. The nortli test site is located approxirnately I 1 5 feet south of the north property line and 1 95 feet east of the west property line. The west test site is approximately 250 feet soutli of the north property line and I95 east of the west property line (Figure Al). Although both of these sites are equal distance from the west property line, the west site is further west than the north site as the west property line is oriented northeast to southwest. A-1 Site soils were described and percolation tested in both areas with negligible slope. The west site is on a crest that slopes approximately l7-l3Yt west towards the west property line. 'fhe location of this drop offlcut-bank near Cit 218 will require a 25-foot setback in accordance with the Regulations. The north site is of sufficient area but enoroaches on the 1O0-foot setback from proposed water supply well in north area of parcel. Setback to the existing lake in the northwest comÊr of property exceeds the S0-foot minimum for both west and north percolation test sites. Croundwater \ryas not encountered in either 8-foot soils observation pit; high seasonal groundwater is estimated to be greater than 8.0 feet, The soil profile logs are summarized below and in Tables I and lA. Dark yellowish brown (1OYR 4/4) clayey sand loam with granular structure oçcurs *om 0.0,9 feet overlyìrg dark yellowish b¡own (1OYR 4/4) clayey sand loam with lenses of sandy clay with granular structure frorn 0.9-8.0 feet maximum depth of excavation. The west site consists of a unifonn profile of alluvium with yellowish red (5YR 5/6) sandy matrix supporting well-rounded pebble- to small boulder-sized clasts. The high seasonal water table estimate of 8.0 feet is based on low antecedenf soil rnoisture content and the lack of soil colorinfredoximorphic features indicative of prolonged soil saturation via groundwater. Table l North Pit Soil Log Description vf= very fine; f:m: medium and; crs: soarse for sand Table lA. 1ü9est Fit Soil Log Description Percolation râtes summarize<l in Tables 2 and 2A. rângc fi'r:rn I4 to 46 niinutes per inch {minlin} ior the nofih tesf site and 7 to 48 minlin for the west site. A.verage percolation rates for the north and west percolation test sites are 22 and 26 mirfin, respectively. Basecl on percolation data, macroscopic tactile soil analysis and estimated depth of the high seasonal water table, the infiltrative surface of the soil treatment area STA/leachfield can occur along a soil depth interval Depth Interval (ft)Soil Description 0-0,9 Dark yellowish brown (10YR 4/4) sand {f-vf)' witir silt; low OM; granular; dry; sage vegetation 0.9-8.0 Brownish yellow 80% (1OYR 6/6) and 20% (10YR 6/8) sand (f-vf) with Z-inch thick lens at 2' interval of clayey sand {Èvfl; low OM; granular laminar structure; dry Ðepth lnterval (ft)Soil Description 0-8.û Alluviurn with yellcwish red {5YR 516} sandy {vÊcrs) sandy matrix supporting well-rounded pebble- to small boulder-sized clasts; low OM; granular with laminar clast struch;re; dry; sage vegetatior A-2 ranging from 2.û to 4.0 feet depth, Site soils are categorizeð asType 2 Soils based on sand textureso granular laminar structure, and percolation rates predominantly within the l6-25 min/in percolation rate range. At the time of installing the O'WTS, soils should not be exçavated under wet conditions to avoid cornpaction and smearing leading to reduction in permeability. Table 2. North Pit Percolation Test Results Table 2A,. TVest Pit Percolation Test Results ID Depth {ft) Time Final Drop (in) Percolation Rate (min/in) 12:54 (start) l:09 l:39 2:t9 2:54 (end) 1 2.t-3.0 3.9*3.75*4"375*5.û'5.625"2.62s 46 2 0.0-1.0 4.625"6.0"8.5"10.0"dry 5.3?s t4 J 2.2-3.2 5.0"6.5'o 8.5"1A"25*dry 5.25 14 4 5.0-6.0 3.875"5.0"6.s"',8.0'9-375"5.5 22 5 3.û*4.0 6.75"8.125"10.0-dry dry 3,25 14 ID Depth (ft) Time Final Ðrop (in) Percolation Rate (min/in) '10:12 {start) It:27 10:5:f ll:27 12:12 (end) 6 2.t-3.0 3.25"3.75"4.5"6.0"6.8?5"3.62s JJ 7 û.0-1.û 4. ?5*5.25"6.0"6.5"7,25*?5 48 I 2.Ð,3.0 4.0"4.75"5.5"6.7s',r dry 2.75 27 9 4.0-5.û 5.0u'6.0"dry dry dry 1.0 15 rû 3.5-4.5 4.5"6.75"dry dry dry 2.25 7 Ä-3 FIGURES FIGURE A3OWTS CROSS SECTIONCR 218 Address TBDNest]{oterEngineering2516 Foresight Circle,Grond Junction, C0 81(s7o) 241-7076#1505.T=USE TOP FACEPLATE PORTCOVER INFILTRATORS WITH WOVEN GEOTEXTILE FABRICCROWN BACKFILLOVER INFiLTRATOR BEDWESTSOILSEXISTINGGROUNDNORTHSOILSSITE3.5'I8'MAXIMUM DEPTH 4.0 FEETMINIMUM DEPTH 2.0 FETTInstollotion Notes:1) Follow Monufocturers Instructionwww.infiltrotorsystems.com2) Screw Pipe Top Port Chomber Foceplote3) Screw Foceplotes ond Units Together4) Instoll Monitoring PortsSCALE1tt:S'50no\otıEorP5?gØa'trcofsì_à<coa HOLGUIN RES. COUNTY RD 218 ADDRESS TBD SHEET: 1 .A STUDIO M TNGINTTRS, LLC 9TRUCTU RAL CO N9 U LTANT9 DRATTTD tsY: MJB DESIGNED BY; MJts DATEr 3.2.2O21 9CALE; A9 Sl-lOWN 25O TRIPP DRIVE RIFLE COLORADO BI650 970-366-8690 WOOD ?o91 PLAN lll lll 10'DlA. CONC. PIER CLR, W/ #4 VERT DWLg @ QUARTER POINTg T,A.F 5/8' DIA, EPOfr RD. (4 EY|BED TO CONC. 10' EÞI|øED 1O COL) BIÎCH àÊ?era¡ïON ll WOOD/ CONCRETE INTERFACE 3f4"= l'-O" ?AD ?ER, 9CHEDULÊ T.O.PIER 98|9" 7C'-1C 1/2" 23'-1/4" ¿ tn Â Y I# 96'*1" 29'-Q"8'-C" T.O.W :\t f- r- rl. 96'-7" 98'-9.7/8', aà\h\JI¡sþ(.f¡\fìxl'-'sôâ-,poo0 |*--+þþoIJa6t'wail,a\^Þ\d "ìtÞS çlcno tvç\/3