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Home My WebLink AboutOWTS Design ReportJohn and Robert Parrington TaJly Ho Construction 0145 County Road 225 Rifle, CO 81650 tallyhoconstl@.sopris .net July 25, 20161 RE: AS-BUILT, Onsite Wastewater Treatment System (OWTS). IRMW TI LLC-MRI Waste Management Facility, 1058 C.R. 100, Garfield County, Colorado SE Job No. 16094.01 Parcel Number: Parcel Number: 2393-363-00-063 Dear Gentleman: Pursuant to County requirements, this letter provides documentation that the new Onsite Wastewater Treatment ..Systems .(OWTS.) recently installed at the above referenced site is in comp1iance with the permitted design. Sopris Engineering inspected the excavations, soils, materials and the installation of the system components at various times during construction, prior to final backfill and after all installations was completed. 111e system constructed on site was designed and built to serve the needs of a commercial facility currently under construction. The installed system wos designed with a maximum treatment capacity of240 gallons per day based on usage with population of 14 employees and 6 person transients. Sopris Engineering performed site visits to inspect and document the as-built conditions of the constructed system. Inspections were coordinated with Tally Ho Construction. The as-built conditions and installation of the new OWTS components is in compliance with Garfield County Regulations; the recommendations and specifications delineated on the civil OWTS design plan, Cl-OWTS Plan , dated 5-4-2016, by Sopris Engineering. The design criteria and system sizing info1mation is summarized below. An As-built OWTS record drawing is attached delineating the As- built descriptions and location of the components . Design Criteria a1td As-built System Comnonent Installation The system was designed based on the design criteria approved for use of Soil Treatment Unit (STU) systems . The OWTS includes the installation of n 1000 gallon 2-compartment concrete septic tank with concrete risers and lids installed at the surface. The tank was installed with an inlet sanitary tee and an outlet effluent filter sanitary tee . A grav ity schedule-40 sewer pipe with a cleanout is installed from the maintenance facility structure to the tank. The soil treatment unit (STU) consists of2 leaching chamber trenches that provide 280 S.F. of total absorption area with treatment across the scarified native soil absorptive surface finished with a 311 leve1ing course of ASTM-33 sand. The septic tank effiuent is equally distributed by gravity, via a distribution box, to the STU. The effiuent is distributed through a concrete distribution box installed with risers and lid at the surface and individual distribution pipes connected to the head end cap of each chamber trench. Observation ports with caps were 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 Jong term acceptance rate (LTAR). j 502 Main Street • Suite A3 • Carbondale, co 81623 • (970) 704-0311 • Fax (970) 704-0313 I SOPRIS ENGINEERING • llC civ i l consultants Sub Surface Conditions and observation AS-BUILT, OWTS lRMW ll LLC-MRI WMF SE Job No. 16094.01 July 25, 2016 Subsurface soil investigations and USDA soil texture method tests were performed by Sopris Engineering on May 3, 2016. The soils were tested to determine the hydraulic loading rate and to confirm the approptiate absorptive surface suitable for conventional absorption systems in native soils. A shallow and deep excavated pit was observed in the North central portion of the site adjacent to the proposed field location. The soils below 6 to 9 inches of mixed surface fill & topsoil consist of medium dense sandy silt loam with moderate granular to slightly blocky structure with some cobbles and gravels. The percentage of cobbles and grnvels below 24 inches was less than 20% in the sandy silt loam to the 7 foot depth explored. The native soils sampled from 2-3 feet below the surface are characterized as a soil type 2 consisting of silt loam texture with moderate granular structure. This soil has an effective loading rate for conventional soil treatment of0.60 gal/S.F./day for a level 1 conventional treatment system. The equivalent percolation rate is assumed to be approximately 16-25 minutes pet• inch. No free water was encountered in excavations on site. No excessive boulders or cobbles were encountered dul'ing excavation. Observations of the soils, in the excavation during construction, appeared to be consistent with the previous subsurface soil investigation . Design Flow The design flow is calculated as follows: The new OWTS shall be based on a minimum 4-bedroom capacity for single family residence. From the Garfield County OWTS Regulation 43; Minimum population based on 2 persons per bedroom for first 3 bedrooms & 1 person per bedroom for each additional bedroom 3 bedrooms @ 2 person /bedroom = 6 persons. l bedrooms @ 1 person /bedroom = 1 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 = 7*75=525 gpd Treatment-Soil Treatment Unit/ Absorption System Design The treatment/absorption field was designed based on utilizing the effective Long Term Acceptance Rate (LT AR) for the native soils and the application of appropriate loading factors for a soil treatment unit system utilizing gravity disldbution to gravelless chamber trenches. The new 11·eatment system and absorption field consist of gravity distribution of septic tank effluent via a distribution box lo individual chamber trenches with treatment across the scarified native .soil absorptive surface with a 3" Jcvcling cow·se of ASTM-33 sand. Long Tenn Acceptance Rate (LTAR) Considering the application of the new state regulation 43: Receiving Wastewater Treatment Level 1; loading rate for silt loam is (0.60 gal./S .F./day) for soil type 2.; Loading factors; (Table 10-2, Gravity application trenches = 1.0) and (fable l0-3, gravelless chambers= 0.7) A(st) = Qd .: A =Area; LT AR= 0.60 Gal/S.F./day for silt loam Qd = flow (gal/day) : 240 gpd L.F. l "" 1.0 Gravity Distribution L.F.2=0. 7 Chambers A(sf) = 240 gpd x 1.0 x 0. 7 = 280 S.F. 0.60 Gal/S.F./day Nwnber of quick-4 chambers: 240 S.F = 24 chambers Used 24 chambers 12 S.F./Chamber AS-BUILT, OWTS IRMW fl LLC-MRI WMF SE Job No. 16094.0 I July 25, 2016 24 Quick-4 chambers in two trenches 50' long by 3' wide with 12 chambers units per trench plus two end caps was installed as delineated on the attached As-Built Record drawing. OWS Operation and Maintenance Ownership of the system and responsibility for mnintenance and repair will remain with the property Owner. The Owne1· is encouraged to retain the services of qualified personnel to inspect the OWTS and to perform all maintenance and repairs necessary to ensure that the system components are maintained in good operating condition and suitable vegetative cover is established on the fields. The components of the OWTS system should inspected within 30 days of being placed into operation and should been inspected and maintained bi- annually. The tank, abso1ption field and other system components shouJd be visually inspected bi~annually for debris, damage, leaks, or other potential probJems. In general, for a properly utilized system, septic tanks should be pumped every 3 -5years. The effiuent filler should be cleaned every six months and at the time of pumping. Absorption fields should be maintained with suitable vegetative cover and kept free of root invasive plants. Positive surface drainage away from the absorption field should be maintained. 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