The URL can be used to link to this page

Home My WebLink AboutOWTS Design Report 10.01.2025October 1 ,2025 Heathcote West LLC 5798 Sweetwater Road Gypsum, CO 81637 c/o Chris Bendon RE: OWTS Design Report, On-site Wastewater Treatment System (OWTS), Guest according to the Healthcote West tracts SB35 subdivision exemption plat rec. #1006809, 4894 Sweetwater Ranch, Garfield County, CO SE, Job No. 34008.01, Parcel No: 186335300028 G-8, New Garfield County Permit # Dear Chris: This letter report presents the applicable findings regarding the design and construction of a new Onsite Wastewater Treatment System (OWTS) at the above-mentioned site, in support of a building permit application to Garfield County. A new OWTS construction permit is required for the proposed usage on the subject property. The OWTS design is based on our evaluation of the site conditions for use in obtaining a Garfield County OWTS construction permit. We have evaluated the existing and proposed site conditions with respect to the operation and installation of a new OWTS in accordance with County OWTS Regulations and State of Colorado Regulation 43. The new system meets all required setback requirements and operational demands for the proposed usage. Based on the physical site features, soils, and proposed building layout, we have prepared a civil OWTS design plan with construction details for permit approval. The design drawing is based on a recent Survey performed by True North Colorado. The design and construction recommendations with specifications were prepared by Sopris EngineeringLLC andare delineated on civil design plans titled Cl-OWTS Site Plan dated 0912612025, included within the complete Building Permit Plan set. nditions and Des Proposed site improvements and expected usage for Guest House-2 result in a design flow of 500 gpd. The system will be constructed to provide for demand dosing of septic tank effluent to an engineered soil treatment area (STA), pursuant to Regulati on 43 design criteria. The OWTS will include a gravity service pipe from the new dwelling to a new 1250-gallon concrete septic tank equipped with a high head effluent pump assembly. The system is designed based on the current design criteria for the use of a pressure dosed chamber trench system. The STA area calculations are based on the design flow, LTAR loading rate for the in-situ soils utilizing applicable multiplier loading rates per Table 10.2 and 3, Category,3 distribution media consisting of shallow pressure dosed chamber trenches installed over native soil. The system will include the installation of an Orenco System bio tube effluent pump assembly for pressure distribution of septic tank effluent to a new pressure dosed chamber trench system. The effluent discharge piping will be installed to connect to a common pressurized manifold with connections to the head of each 512 li{ain $i:eet, Suila A3, earbcnci:le, e0 Bi6:3 97A-7*4-0311 OWTS Design and Construction Sweetwater #t"ii."t-*ilff Oct. 1,2025 Page2 chamber trench with custom perforated distribution laterals. Each chamber trench will have appropriate inspection poft cleanouts and appurtenances. Desien Calculations OWTS The proposed residential facility design includes a 3-bedroom single family residence. The 3'd bedroom is a bunk room with extra bed for up to 2 adults withl child or 3 children. The design flow is based on a total residential population of6 persons. Per County adopted State Regulalion 43, Design Flow Criteria: Minimum population is based on 2 persons per bedroom for the first 3 bedrooms. Design capacity : 2 x 3 : 6 persons @ 75 gallperson/day plus 50 gpd extra bed, Max. Design flow (Qd) gallonslday: (# of people) x (avg. flow) gallperson/day + 50 gpd extra bed. Design flow Qd : 6 * 75 : 450 + 50 :500 gpd Septic Tank Design:2-Day detention time : 500 x 2 : 1000 gallons required plus 250 gal for dosing. Use a 1250 gallon, two-compartment concrete septic tank with a high head pump assembly Sub Surface Conditions and Testing: A Subsurface soil investigation was performed by CTL on December 17, 2024 to develop recommendations for the foundation, floor slab, below grade walls and subsurface drainage design. The subsoil conditions around the proposed dwelling structure were evaluated from soil samples obtained from two excavated profile pits. Samples of.the subsoils obtained during the field exploration were tested in the laboratory to determini their classification, compressibility, natural moisture content, and finer than sand size gradation analyses and other engineering characteristics. The subsurface profile encountered in the pits generally consists of sandy clay loam. A subsurface soil investigation and site assessment was performed by Sopris Engineering in on November 18,2024, to evaluate the soils conditions and determine the effective Long Term Acceptance Rate (LTAR) for onsite Wastewater Treatment System (OWTS) Soil treatment area (STA), The soils in the several development envelopes explored were sampled and characterized by application of the USDA visual/tactile soil texture method analysis from samplesin2 profile pits per building site. Two profile pits were observed within the guest cabin 3 building envelope. 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 moderately sloped to flat terrain. r:. t; ,t ii:: iri;:-:il :1:: ,ir l, : ! ,. 5il2 lt:lain 51ree!, Suit* A3, Cari:cr:dale, CC 81f]-3 970-7t*,-*3a1 OWTS Design and Construction Sweetwater Ranch Guest Cabin 4 Garfield County SE Job No. 34008.01 OcL.1,2025 Page 3 Profile Pit-GC-4 A The soils below approximately 6 inches of topsoil consists of brown silty clay loam texture soil with slightly blocky to granular structure of moderate structural grade to a depth of 2 feet containing no scattered gravel or rock content. The underlying Soils to a depth of 7' consist of tan silty clay loam with fine granular structure of moderate structural grade with gravelly rock fragments <30oA, underlain by light brown clay loam to the 12' depth explored. No free water or evidence of seasonal high groundwater was encountered in the pit excavation. Profile Pit-GC-4 B The soils below approximately 6 inches of topsoil consists of brown silty clay loam texture soil with slightly blocky to granular structure of moderate structural grade to a depth of 3 feet containing no scattered gravel or rock content. The underlying Soils at 3' consist of silty clay loam with fine granular structure of moderate structural grade with gravelly rock fragments <30olo, underlain by weathered bedrock to the refusal 8' depth explored. No free water or evidence of seasonal high groundwater was encountered in the pit excavation. The native soils sampled from 2'-4' below the surface, in both profile pits, are charucterized as a soil type 3 consisting of silty clay loam texture of moderate grade with granular structure. The tactile soil test ribbons were over | 314-inch long. The Soil Type-3 has an effective loading rate (LTAR)of 0.35 Gal/S.F./day for a level I conventional treatment system. Based on the testing results, existing topography, vegetation and observation of site features the soils appear and are assumed to be relatively consistent across the site. The soils are suitable forthe installation of an STA consisting of multiple gravelless chambertrenches that will be fully pressure dosed meeting the requirements under sections (43.10.C,D,E,F&H and43.1l.C.). Additional soil evaluations will be performed by the engineer during construction to verifu the soils in the entire STA field excavation prior to installation of the OWTS components. Chamber Treatment Unit/ Abso rnfion Svsfem T)esipn The treatment/absorption trenches are designed based on utilizing the effective Long Term Acceptance Rate (LTAR) for native soils and the application of appropriate loading factors for a treatment level-l system utilizing pressure dosed chamber trenches. The new treatment system will consist of pressure dosed chamber trenches with custom perforated distribution laterals, in accordance with Regulation 43 sections (43.10(C), 43.13.8..1.d, Table l0-2 and Table 10-3 as approved by CDPHE for this technology. Long Term Acceptance Rate (LTAR) Receiving septic tank effluent, a treatment level-l system for chambers requires the infiltrative surface being at least A-feet above a limiting layer (43.8, Table 7-2.D; Maximum hydraulic loading rate for TLI effluent is 0.35 gal./S.F./day) (Table 10-l) being the long-term acceptance rate of the Type 3 receiving soil. 502 \iain Sl:'e*i, Suite A3, ea:'bcnilale, eO 816:3 97C-714-03i I OWTS Design and Construction Sweetwater Ranch Guest Cabin 4 Garfield County SE Job No. 34008.01 OcL.1,2025 Page 4 A(sO: Od x L.F.l x L.F.2.: LTAR A: Area; LTAR: 0.35 gallS.F./day for silt loam Qd: flow (gaVday) for OWTS :675 gpd L.F.1:0.8 pressure dosed trench application L.F .2:0.7 Gravelless chambers OWTS: A(s| :300 gpd x 0.8 x 0.7: 800 S.F. 0.35 Gal/S.F.lday Number of Quick-4 Infiltrator chambers 4'x3'x8"chambers: 800 S.F : 66.8 Infiltrator Quick-4 chambers; Use 68 chambers l2 S.F./Chamber Number of Equivalent Arc-36 chambers 5'x3'xl2"chambers 800 s.F 53.4 chambers; Use 54 chambers 15 S.F./Chamber Install 68 Quick-4 Infiltrator chambers in 4 trenches 70' long by 3'wide with l0 chamber units per trench plus two end caps as delineated on the plan. Alternative use 54 Arc-36 chambers in 4 trenches 70' long by 3'wide with 14 chambers units per trench with ends caps. A 4" veftical inspection port riser to be installed from the molded penetration port on each chamber end cap or each end chamber in the trench. Effluent Distribution System The septic tank effluent will be pressure discharged to a common manifold pipe, installed at the head of the trenches, via a 1.5" transport pipe from the high head pump discharge assembly in a biotube filter vault set in the second compartment of the 1,250 gallon tank The minimum slope of the transport pipe from the tank's dosing compartment to the manifold shall be installed at a minimum 2%o slope to allow for drain back to the tank. The distribution system will be installed for effluent to be equally distributed across the absorptive surface in each trench via individual custom perforated pressure distribution laterals connected to the manifold pipe. The distribution laterals will be installed on the infiltrative surface, under the chambers, along the entire length of each trench. The 5132-inch orifices will be drilled on 2,5' centers oriented upward along the length of the distribution lateral. A ball valve will be installed on the terminal end of each distribution lateral centered below the 4" inspection port, housed in a 6" valve box with lid set 2" aboye surface grades. :.r :: :r_- | : l :rir :r: :i r:. .i - : : i 5Cl Main 6ireet, Suii* A3, earbondale, CC $,]6?3 970-7C4-0311 OWTS Design and Construction Sweetwater Ranch Guest Cabin 4 Garfield County SE Job No. 34008.01o"';l!31 Construction and Inspections prior to construction of the permitted system, the engineer should be contacted by the contractor and construction project manager well in advance to provide adequate time to discuss the system components with the contractor, answer questions, resolve any confliet issues and schedule inspection site visits based on construction progress. A pre-OWTS construction meeting and calls are essential and required prior to installation of the OWTS. The engineer, prior to excavation shall inspect the staked location, of the proposed treatmentlabsorption bed and tank. All septic system components shall be staked in the field for approval by the Engineer prior to excavation. During initial construction the engineer will evaluate the soils in the location of the absorption treatment field to confirm design assumptions made and existing conditions. The engineer will provide construction recommendations and adjust the field layout and sizing if needed with discussion of construction procedures. As necessary a revised Construction document drawing will be submitted to the County as needed if changes are iequired. All installations shall be inspected, surveyed, documented and reported/delineated in the Certification letter and As-Constructed drawing. County Regulations require that the Design Engineer of record perform site inspections of the permitted system during construction and provide "As-Built" documentation of the installed system to the County after construction is complete. photo documentation during construction and site system inspections is required to be performed by the contractor and Engineer. System component installation inspection and r.ui"* of photo documentation is required of the exposed system components prior to backfilling. Photo documentation will be included with the As-Built Record drawing submittal package to finalize the OWTS permit. Therefore, the Engineer should be contacted as needed and notified of the construction progress and scheduling to allow time to schedule specific inspection times. The county environmental health department needs to be contacted at least 48 hours prior t-o $31 backfill of components to provide advanced notice of construction schedule in order to perform a final inspection of the in place components. The Garfield County environmental health contact number is 970-945-6614 x 8106 (main office). ..ii lt! - i::1 tlii:: :i::.-l ::.i. 50t lvlaln Sl:eei, Suile A3, ea*r:nd*lc, CC Bl6?3 97t'-7il4-Ay1 OWTS Design and Construction Sweetwater Ranch Guest Cabin 4 Garfield County SE Job No. 34008.01 Oct. 1,2025 Page 6 OWTS Oneration and Maintenance All components of the engineered OWTS shall be inspected on a regular basis and be properly maintained. The responsibility for repair and maintenance of the system will remain with the property Owner. The owner shall retain the services of qualified personnel to inspect the OWTS and to perform all maintenance and repairs necessary to ensure that the system is in good operating condition and follows the manufacturer's performance requirements. The operating components of the OWTS shall be inspected by the engineer within 30 days of being placed into operation and thereafter every six months by the owner or qualified service provider. In general, for a properly utilized system, septic tanks should be pumped every 3-5 years. The effluent filter should be cleaned every six months andat 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. If you have any questions or need any additional information, please call. Sincerely, SOPRIS ENGINEERING, LLC PaulE. Rutledge Design Engineer Yancy Nichol, PE Principal fi/, 28377 20;5{.Uc ':; :i :tr: i:r.,r':i_: ;i ..i:, :.! : 5ili Main $lraei, Suite A3. C*$r:nd*le, i* Bl6?3 970-704-03Ji