The URL can be used to link to this page

Home My WebLink AboutOWTS Final Installation Observations 05.06.2022May 6, 2022 502 Main Street • Suite A3 • Carbondale, CO 81623 • (970) 704 -0311 • Fax (970) 704 -0313 S OPRIS E NGINEERING • LLC civil consultants Jeffrey K & Worthen, Angela F, Huber 524 County Rd 259 Silt, CO "Jeff Huber" <jklineman44@yahoo.com> RE: As-Constructed–Onsite Wastewater Treatment System (OWTS), Huber Residence, 524 County Rd 259, AKA Rolling Meadows Lot: Tr G, Section 34 T5S R92W 6th PM, Garfield County, Colorado SE Job No. 31260.01 Parcel No: 212734200159, Previous Garfield County ISDS Permit: 1892, 9-9-91 Current Garfield County ISDS Permit: SEPT-7421, Issue Date 04-25-22 Dear Steven: 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 general 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 replacement soil treatment area (STA) absorption field, septic tank and dosing siphon/basin and distribution component installations were designed and constructed to serve the proposed usage on the subject 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 Contractor (Sacred Ground Excavation, LLC) that installed the 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 and the OWTS design Report dated 6-23-21, by Sopris Engineering. The design criteria and system sizing information is summarized below. OWTS Design Criteria and Sizing The replacement OWTS is designed for a treatment capacity of 525 gallons per day based on the design wastewater flow to serve a 4-bedroom residence in accordance with Table 6-2 values, Section 43.6, A.4. This design provides for an upgrade to the existing 1250 gallon septic tank, however the tank was compromised and was replaced with a 1,500 gallon two compartment plastic septic tank. The upgraded included the installation of a 500-gallon plastic dosing tank with dosing siphon in series with the septic tank placed within the landscape lawn embankment. The dosing siphon automatically discharges septic tank effluent to a distribution box. All tank risers extend to 3” above finish surface grades. A new outlet effluent filter was installed on the new septic tank along with appropriate pipe connection to the new dosing tank in series. A gravity schedule-40 or SDR-35 effluent pipe from the new dosing tank/siphon discharge assembly was installed to the new replacement STU absorption field with appropriate stepped fittings and cleanouts to a new distribution box at the head of the STU chamber trench field. The new replacement soil treatment unit (STU) consists of leaching chamber trenches that provide 662 S.F. of total absorption area. The septic tank effluent will be gravity discharged through a new 4-inch schedule-40 or SDR-35, installed 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 of 6 chamber trenches. Observation ports with caps are installed on each end chamber unit. 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. The existing well serving the residence, (Permit No. 39336-F) is located over 200 feet South Southeast of the proposed field area. Our design is outlined below and delineated on the attached C-1 OWTS plan. Design Calculations OWTS Huber Residence As-Constructed OWTS 524 CR 259 SE Job No. 31260.01 May 6, 2022 Page2 Design population is 3 bedrooms x 2 persons + 1 bedroom x 1 person = 7 persons total. Gallons per day per person =75 gal/person/day, No peaking factor Design capacity = Max. Design flow (Qd)gallons/day = (# of people) x (avg. flow)gal/person/day. Design flow Qd = 7 + 75 = 525 gpd Septic Tank Design: 2-Day detention time = 525 x 2 = 1,050 gallons required. A 1,500 gallon plastic two-compartment primary septic tank is installed in series with a 500 gallon pump basin with a simplex dosing siphon assembly. Sub Surface Conditions and Testing A site specific subsurface soil evaluation was performed by Sopris Engineering, March 23, 2022, in the vicinity of the proposed OWTS field. Two profile pits were excavated, by backhoe, to a depth of 7-8 feet in the vicinity of the proposed soil treatment area (STA). The soils encountered in open pit excavations were sampled and characterized by application of the USDA soil texture method test. The soils were tested to determine the presence of any limiting soil or hydrological conditions, assess appropriate hydraulic loading rate, range of absorptive surface levels and to assess appropriate treatment level design alternatives for installation of treatment/absorption systems the in-situ native soils. The soils below 12 inches of topsoil consist of medium dense silt loam from 1.0 to 7 feet below the surface. The native soils from 2 to 3 feet below the surface are characterized as a soil type 2 consisting of sandy silt loam texture of granular with rock content less than 35%. The tactile soil test ribbons were approximately 1 inch long. the soils below 4 feet contained increased fine sand and were denser with slightly granular to massive weak structure to depths of 7-8 feet. The type 2 soil has an effective loading rate for conventional soil treatment of 0.5 to 0.6 Gal/S.F./day for a level 1 conventional treatment system. The equivalent percolation rate is 26-40 minutes per inch. No free water or other limiting conditions were encountered or observed in the profile pit excavations on site. Groundwater levels are expected to be below 12 feet from the existing surface grades. Treatment-Soil Treatment Unit/ Absorption System Design The treatment/absorption field is 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 dosed effluent via a dosing siphon (Fluid Dynamic 200 Series, Model 207) to a distribution box to equally disperse approximately 90 gallons per cycle to the six gravelless chamber trenches. The new gravity dosed volumetric distribution of septic tank effluent to the individual chamber trenches insures treatment across the native soil absorptive surface and adequate recovery time between dosing cycles. Based on design flow the system will be dosed 5 times per day. Realistically the system will be dosed 2-3 times per day. The shallow STU trenches were installed with a maximum depth to the absorptive surface of 36 inches from finish surface grades and backfilled with approximately 3-inches of final grading topsoil mounded over the trench rows placed to allow positive drainage away across the surface. Chambers were installed level in each individual trench overlying the 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 is maintained between the individual trench sidewalls. Field Sizing: Long Term Acceptance Rate (LTAR) Receiving Wastewater Treatment Level 1; Soil type 2A loading rate for silt loam with granular to weak massive structure at depth is (0.5 gal./S.F./day). Loading factors; (Table 10-2, Dosed Siphon trenches = 0.9) and (Table 10-3, gravelless chambers = 0.7)