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Home My WebLink AboutOWTS Installation Observations 11.29.2021November 29, 2021 502 Main Street • Suite A3 • Carbonda le, CO 81623 • (970) 704 -0311 • Fax (970) 704 -0313 S OPRIS E NGINEERING • LLC civil consultants Devon & Craig Spaulding 10441 CR 311, Silt, CO 81652 dspaulding@mountainfamily.org cspaulding19@gmail.com RE: Design Report–Onsite Wastewater Treatment System (OWTS), Spaulding Residence, 10441 CR 311, Silt CO, AKA Record Ranch Subdivision Exemption Lot 2, Garfield County, Colorado SEJob No. 31094.01 Parcel No: 240124200275. Dear Devon and Craig: Pursuant to County requirements, this letter provides documentation that the Onsite Wastewater Treatment System (OWTS) recently installed at the above referenced site is in compliance with the permitted design. The newly constructed absorption field and tank installations were designed and constructed to serve a new 3-bedroom residence. Sopris Engineering performed site visits to inspect and document the as-constructed conditions of the OWTS. Inspections were coordinated with the property owner that installed the system components. The as-built conditions and installation of the new OWTS components are in compliance with Garfield County Regulations; the recommendations and specifications delineated on the civil C1 OWTS plan drawing dated 05-25-2021 and the OWTS design Report dated 05-25 -2020 by Sopris Engineering. The design criteria and system sizing information is summarized below. Summary Design Criteria The constructed OWTS was designed for a treatment capacity of 450 gallons per day based on the design wastewater flow to serve a 3-bedroom residence in accordance with Table 6 -2 values, Section 43.6, A.4. The new OWTS utilizes a new 1,060-gallon two compartment reinforced plastic septic tank within the lawn area west of the replacement dwelling structure. The tank was installed with sealed risers and lids to the finish grade surface, an inlet sanitary tee and an effluent filter outlet sanitary tee in the second compartment.. The new soil treatment unit (STU) consists of leaching chamber trenches that provide 525 S.F. of total absorption area. The septic tank effluent is gravity discharged through a new 4-inch SDR-35 gravity sewer pipe installed at a minimum 1% slope, to the STU via a distribution box. The effluent is equally distributed from the distribution box via 4” distribution pipes connected to the head end cap of each chamber trench. Observation ports with caps were installed on the distal end chamber unit on each trench. The design is in compliance with the current County regulations with design calculations based on the soil type, texture and structure with an appropriate long term acceptance rate (LTAR). The installed system meets all required setbacks and was installed within the general location indicated on the plan. The existing well serving the residence, (Permit No. 158487) is located over 100 feet east of the proposed field area. Our design is outlined below and delineated on the attached C-1 As- Constructed OWTS Record drawing. Design Flow The new OWTS is designed for a treatment capacity of 450 gallons per day based on the minimum design wastewater flow to serve an equivalent 3-bedroom single family dwelling in accordance with Table 6-2 values, Section 43.6, A.4. Regulation 43: Minimum population based on 2 person per bedroom for the minimum 3 bedroom capacity = 4 persons. Gallons per day per person =75 gal/person/day, No peaking factor Max. Design flow (Qd)gallons/day = (# of people) x (avg. flow)gal/person/day. Design flow Qd = 6*75=450 gpd Spaulding Residence AC-OWTS, 10441 C.R. 311 SE Job No. 31094.01 November 29, 2021 Page2 Septic Tank Design The septic tank capacity required for a minimum 48 hour retention time is calculated as follows: V = 450 gal/day * 2 = 900 gallons. Installed a minimum 1,060 gallon, two compartment reinforced plastic septic tank with an inlet sanitary tee and effluent filter outlet sanitary tee in the second chamber. Tank was installed with sealed risers and lids to the finish grade surface. Sub Surface Conditions and Observation A subsurface soil investigation and site assessment was performed by Sopris Engineering in on May 17, 2021. The soils in the proposed field envelope area were sampled and characterized by application of the USDA visual/tactile soil texture method analysis from samples in two profile pits. The soils below 6 inches of topsoil consist of medium dense slightly sandy silt loam texture soil with slightly blocky to granular structure to a depth of 8 feet. The soil profile contains less than 2% scattered gravel or rock content to the 8-feet depth below the surface grades. No free water was encountered in the pit excavations. Seasonal high Groundwater levels are expected to be below 10 feet from the existing surface grades on the relatively flat terrain. The native soils sampled from 2-3 feet below the surface, in the vicinity of the proposed field, are characterized as a soil type 2 consisting of silt loam texture with granular structure. This soil has an effective loading rate for conventional soil treatment of 0.6 Gal/S.F./day for a level 1 conventional treatment system. The equivalent percolation rate is assumed to be 20-30 minutes per inch. The soils are suitable for a shallow conventional shallow absorption field consisting of gravelless infiltration chamber units. Treatment-Soil Treatment Unit/ Absorption System Design The treatment/absorption field was designed based on utilizing the effective Long Term Acceptance Rate (LTAR) for the native soils and the application of appropriate loading factors for a soil treatment unit system utilizing gravity distribution to gravelless chamber trenches. The new treatment system and absorption field consists of gravity distribution of septic tank effluent via a distribution box to individual chamber trenches with treatment across the native soil absorptive surface. The shallow STU trenches were installed with a maximum depth to the absorptive surface of 30 inches from finish surface grades and backfilled with at least 4-inches of final grading topsoil mounded over the trenches placed to allow positive drainage away from the surface. Chambers were installed level in native soil. Each trench was constructed level along the contours with successive trenches installed following natural contour grades accordingly. A minimum separation distance of 4 feet was maintained between the individual trench sidewalls. Long Term Acceptance Rate (LTAR) Receiving Wastewater Treatment Level 1; Soil type 2 loading rate for a clay loam is (0.6 gal./S.F./day).; Loading factors; (Table 10-2, Gravity application trenches = 1.0 ) and (Table 10-3, gravelless chambers = 0.7) A(sf) = Qd x L.F.1 x L.F.2 .: A = Area; LTAR LTAR = 0.6 Gal/S.F./day for clay loam Qd = flow (gal/day) = 45 0 gpd L.F.1=1.0 Gravity Distribution L.F.2=0.7 Chambers A (sf) = 450 gpd x 1.0 x 0 . 7 = 525 S.F. 0.6 Gal/S .F ./day Number of Quick-4 Infi ltrator chambers 4'x3'x l 2"chambers: 525 S.F = 44 c hambers; Install ed 44 chambers 12 S .F ./Chambe r Spau lding Residence AC-OWTS, 1044 1 C.R. 31 I SE Job No. 31094.0 I November 29, 2021 Page3 44 Quick -4 Infil trator c hambers we re installed in four trenches 46' long by 3' wide w ith 11 chamber units per trench. All 4 trenches were installed wi t h end caps as delineated on t he p la n . The septic tank effluent is g ravity d istri buted to t he head of each chamber trench via individual d ist ri bution p ipes from a distrib ution box. O WTS Operati on a nd Maint e nance Ownershi p of t he system and responsibility fo r maintena nce and repair will remain wi t h the property Owner. The Owner is encouraged to retain the services of qua lified personnel to inspect the OWTS and to perfor m all maintenance an d rep airs necessary to ensure t hat t he syste m components are mainta ined in good operating condi t ion and suitable vegetat ive cover is establ ished on t he fields . The compone nts of the OWTS system should be in spected wi thin 30 days o f being p laced into operation and shou ld be inspected and mai ntained bi-annua ll y . T he tank, absorption fie ld and other system components should be visually inspected bi-annually for debris, damage, leaks, or other potential problems. In gene ra l, for a properl y uti l ized syst em, sep t ic tanks should be pumped every three -five years. Th e effluent filte r should be cleaned every six months and at the time of pumping . Absorption fie lds shou ld be maintained wit h su itab le vegeta tive cover and kept fr ee o f root invasive pla nts . Posit ive surface d rainage away fr om the absorption fie ld should be maintai ned . If you have a ny quest ion or need any a dditional informat io n, please c al l. Sincerely, SOPRIS ENGINEERING, LLC Paul E . Rutledge Design Engin eer 283 -~u-29, 2 ~] ... ~~ .. :· ........ . ,.,._ ,.~ <>, -~~,10NA Yanc Princip al