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Home My WebLink AboutOWTS Installation Observations 09.05.2024September 5, 2024 502 Main Street • Suite A3 • Carbondale, CO 81623 • (970) 704-0311 • Fax (970) 704-0313 S OPRIS E NGINEERING • LLC civil consultants Pena, Mario D PO Box 1904, Rifle, CO 81650 "Mario Pena" <mario@madiganco.co> RE: As-Constructed Report–Onsite Wastewater Treatment System (OWTS), Pena Residence, 403 Rodeo Drive, Rifle, CO, Lot 43 Grass Mesa Ranch, Garfield County, Colorado SE Job No. 34065.01 Parcel No: 217734300375. Garfield County OWTS Permit No. SEPT-8459 Dear Mario: Pursuant to County requirements, this letter provides documentation that the Onsite Wastewater Treatment System (OWTS) upgraded components recently installed at the above referenced site is in compliance with the permitted design. Sopris Engineering inspected the excavations, soils, materials and the installation of the system components during construction, prior to final backfill and after all installations were completed. The installed absorption field and tank was designed and constructed to serve the 3-bedroom residential property. Sopris Engineering performed site visits to inspect and document the as-constructed conditions of the OWTS. Inspections were coordinated with the property owner and the Contractor, which installed the new system components. The as-constructed conditions and installation of the new OWTS components is in compliance with Garfield County Regulations; the recommendations and specifications delineated on the civil design plans, C1- OWTS Plan, dated 06-05-2024, prepared by Sopris Engineering with previously submitted survey plat information, architectural site plan, GIS and aerial mapping. The design criteria and system sizing information is summarized below. Summary Design Criteria The OWTS was designed for a treatment capacity of 450 gallons per day based on the design wastewater flow to serve a minimum 3-bedroom residence in accordance with Table 6-2 values, Section 43.6, A.4. A new 1,060 gallon two-compartment reinforced plastic septic tank was installed off the northwesterly corner of the structure. Sealed plastic risers with lids were installed on the new septic tank along with appropriate pipe connections to the new tank utilizing the appropriate fitting adaptor rings for the tank and riser. The gallon 2-compartment septic tank was installed with appropriate sanitary tees, outlet effluent filter with risers and lids at the surface. A gravity SDR-35 PVC sewer pipe section with two-way cleanout was installed between the tank inlet on the gravity sewer line and the residential structure. The STA consists of leaching chamber trenches that provide 900 S.F. of total absorption area in a trench configuration. The septic tank effluent is gravity discharged through a 4-inch SDR-35 PVC pipe, installed at minimum 1.5% slope, to the STA via a plastic 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 are installed on the proximal and distal ends of each chamber trench and housed in valve boxes set just above finish surface grade. 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 designed system meets all required setbacks and will be installed within the general location indicated on the plan. AC-OWTS, Pena Residence 402 Rodeo Drive CR 228, Rifle, CO SE Job No. 34065.01 September 5, 2024 Page2 Design Flow The design flow is calculated as follows for the minimum design capacity of an equivalent 3-bedroom residential dwelling. The OWTS is designed for a treatment capacity of 450 gallons per day based on the design wastewater flow in accordance with Table 10-1 values, Section 43.6, A.4. Regulation 43: Minimum population based on 3 bedrooms at 2 persons per bedroom equating to 6 persons. The Design flow is calculated based on residential usage of 75 gal/person/day, Max. Design flow (Qd) gallons/day = (# of people) x (avg. flow)gal/person/day. Design flow Qd = 6*75=450 gpd Septic Tank Design The septic tank capacity required for a minimum 48 hour retention time is calculated as follows: V = 300 gal/day * 2 = 600 gallons. Use a minimum 1,000 gallon 2-compartment septic tank. The tank to be installed with risers and access lids set a minimum 3 inches above finish grade surface. Sub Surface Conditions and Testing A subsurface soil investigation and site assessment was performed by Sopris Engineering in on June 2, 2024. 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. No evidence of seasonal high ground water, redox conditions or any other limiting condition was observed in the profile pits. Groundwater levels are expected to be below 20 feet from the existing surface grades on the relatively flat terrain. The soils are suitable for a shallow conventional absorption field consisting of gravelless infiltration chamber units. Profile Pit-1 The soils below approximately 3 inches of topsoil consist of moderately dense clay loam texture soil with slightly blocky to granular shape of moderate structural grade to a depth of 4 feet containing less than 5% scattered gravel or rock content. Evidence of thin scattered lenses of very friable calcareous deposits at variable depths was encountered in Profile pit-1. Soils below 4 feet underlying the calcareous deposits are slightly rocky consisting of up to 25% scattered basaltic gravel, rock and small boulder content in the Clay loam soil matrix to the profile pit depth of 8- feet. No free water was encountered in the pit excavation. Profile Pit-2 The soils below approximately 6 inches of topsoil consist of moderately dense silt loam texture soil with slightly blocky to granular shape of moderate structural grade to a depth of 5 feet containing less than 5% scattered gravel or rock content. An 18 to 30 inch layer of calcareous deposits at variable pitched depth from 24 to 54 inches below surface grade was encountered in Profile pit-2. Soils below 5 feet and/or underlying the 30 degree pitched calcareous layer are slightly rocky consisting of up to 20% scattered basaltic gravel, rock and small boulder content in the Clay loam soil matrix to the profile pit depth of 8-feet. No free water was encountered in the pit excavation. The native soils sampled from 2-3 feet below the surface, in the vicinity of the proposed field, are characterized as a soil type 3 consisting of slightly blocky to granular brown clay loam texture with moderate structural grade. The brown clay loam soil tactile test ribbons were 1-inch to 1 ¾-inch long. Soil types 3 has an effective loading rate for conventional soil treatment of 0.35 Gal/S.F./day for a level 1 conventional treatment system. The interspersed calcareous soil material, at variable depths has granular shape, weak friable structural grade and exhibits tactile test ribbons approximately 1-inch long being consistent with a Type 2 soil however is considered Type 3 due to the clayey fines present. The equivalent percolation rate of these soils is assumed to be 41-60 minutes per inch.