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HomeMy WebLinkAboutOWTS Design Report 10.19.2022October 19,2022 Lyndsay and Garret Jammaron 4909Highway 82 GlenwoodSprings, Colorado 8 1601 RE:Design Report-Onsite Wastewater Treatment System (OWTS), Jammaron Residence, TBD, Deer Park Court Glenwood Springs, Sunlight Parkway, Remainder Parcel, M/8, Garfield County, Colorado SE, Job No. 302105.01 Parcel No: 218534400021, Garfield County Permit:- Dear Lyndsay and Garuet: This letter report presents the applicable findings in regard to the design and construction of a new Onsite Wastewater Treatment System (OV/TS) at the above referenced Site, in support of a OWTS construction permit application to Garfîeld County. The OWTS design is based on recent site assessment observations by Sopris Engineering of existing physical site features, conditions and geotechnical soils evaluation with respect to the proposed residential usage and applicable regulatory design criteria in accordance with State and County OWTS Regulations. The design recommendations, specifications and construction details are delineated on the attached OWTS permit/construction plan that was prepared with GIS, Lidar, Survey Plat information and aerial mapping. The design criteria and system sizing information is summarized below. Summarv Desiqn Criteria The new OWTS is designed for a treatment capacity of 600 gallons per day based on the design wastewater flow to serve a 5-bedroom residence in accordance with Table 6-2 values, Section 43.6, A.4. The OWTS will utilize a new 1,500 gallon 2- compartment and a new 500 gallon 1-compartment, reinforced plastic septic tanks installed in series adjacent to the proposed driveway within a graded landscape area south of the garagelshop dwelling structure. The new 1,500 gallon septic tank will be installed with ribbed PVC risers with fiber lids at the surface, inlet sanitary tee, and an outlet effluent filter sanitary tee. The new 500 gallon septic/dosing tank will be installed with an Orenco biotube high head effluent pump assembly. A 1.S-inch schedule-4O effluent transport pipe from the discharge assembly in the septic/dosing tank will be installed to an automatic distribution valve (ADV) up gradient near the new STA absorption field with individual 1.5-inch schedule-4O distribution pipes installed to a common manifold pipe at the head of 2 paired chamber trenches. The soil treatment Area (STA) will consist of leaching chamber trenches that provide 630 S.F. of total absorption area to be installed at shallow depths not to exceed 30" below existing surface grades. The septic tank effluent will be pressure discharged through the ADV for alternative dosing of two pairs of the 4 full pressure dosed trenches. The effluent will be equally distributed along the length of each trench via a custom perforated 1.5-inch schedule-4O distribution lateral installed on the absorptive surface from the head to the terminal end cap of each trench. Observation ports with caps will be installed on each end chamber unit. Each terminal end of the distribution lateral will be capped with a 1.5-inch ball valve centered under the inspection port. 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 onsite well, serving the residence, (DWR Permit No. 268839) is located over 175 feet southwest of the proposed field area. Our design is outlined below and delineated on the attached C-6.0 OWTS plan. 502 Main Street a Suite A3 a Carbondale, C0 81623 a 970 704-031 1 Fax (970) 704-031 3 SoPRrs tttcmttnIlG o 11G civil consultants L1'ndsay And Garret Jammaron Residence OV/TS, TBD, Deer Park Court Glenwood Springs SE Job No. 32105.01 October 19,2022 Page2 Desisn FIow The design flow is calculated as follows for the total curent and design waste flows of the existing single family dwelling. The OWTS is designed for a treatment capacity of 600 gallons per day based on the design wastewater flow to serve a 5-bedroom capacity residence in accordance with Table 6-2 values, Section 43.6, A.4. Regulation 43: Minimurn population based on 2 person per bedroom for the first 3 bedrooms : 6 persons and 1 person per bedroom for each additional bedroom : 2 persons for a total of 8 persons at 7 5 gallperson/day. Design flow (Qd)gallons/day: (# of people) x (avg. flow)gallperson/day. Design flow Qd:8*75:600 gpd Septic Tank Desisn The septic tank capacity required for a minimum 48 hour retention time is calculated as follows: V:600 gallday * 2= 1200 gallons.lnstall a 1,5OO-gallon,2-compartmentand a 5OO-gallon l-compartment reinforced plastic septic tanks installed in series for a total tank capacity of 2,000 gallons. The 5OO-gallon septic/dosing tank will be equipped with a biotube effluent pump vault. Sub Surface Conditions and Observation A subsurface soil investigation and site assessment was performed by Sopris Engineering on April 14,2022.The soils in the proposed field envelope area were sampled and characterized by application of the USDA visual/tactile soil texture method analysis. The subsurface conditions were evaluated by excavation of two exploratory pits in the building envelope and one profile pit in the proposed OWTS field area. The soils below 6 to 9 inches of topsoil consist of medium dense sandy silt loam soil with less than 2%o scattered gravel or rock content to 7 feet below the surface grades. The soils appear to be consistent across the site from observations in the excavated profile pits. The native soils sampled from 2-3 feet below the surface are characterized as a soil type 2 consisting of sandy silt loam texture with blocþ granular structure. This soil has an effective loading rate for conventional soil treatment of 0.6 Gal/S.F.iday for a level I conventional treatment system. The equivalent percolation rate is assumed to be 20-30 minutes per inch. No free water was encountered in excavations on site. Seasonal high Groundwater levels are expected to be below 20 feetfrom the existing surface grades. The soils are suitable for a conventional shallow absorption field consisting of pressure dosed gravelless infiltration chamber units in a trench configuration. Additional observations and soil evaluation will be performed during construction, by Sopris Engineering in the area of the proposed absorption fîeld to confirm the previous soil evaluation. Sopris Engineering will observe new profile pits in the area of the proposed absorption field to veri$ the in-situ native soil's characteristics. If soil conditions encountered require adjustments to design criteria or the design plan, notice will be made to County EHD and applicable revisions to design/construction plans and report will be submitted. The results of the additional soil evaluation and soil characterizationwill be included in the As-Constructed documentation. Treatment-Soil Treatment Unit/ Absorption Svstem 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 area system utilizing pressure distribution to full pressure dosed gravelless chamber trenches. The new treatment system and absorption field will consist of pressure dosed distribution of septic tank effluent from a biotube high head pump assembly vault to an automatic distributing valve with individual distribution pipes routed to each paired chamber trench installed with custom perforated distribution laterals. Each of the paired trenches will be alternately dosed with equal distribution across the native soil absorptive surface. Lyndsay And Garret Jammaron Residence OWTS, TBD, Deer Park Court Glenwood Springs SE Job No. 32105.01 October 19,2022 Page3 The shallow STU trenches shall be 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 over the trenches placed to allow positive drainage away from the surface. Chambers shall be installed level in native soil over the scarified absorptive surface at the bottom of each trench excavation. Each trench will be constructed level with minimum exaction depths. A minimum separation distance of 4 feet will be maintained between the individual trench sidewalls. The engineer, prior to installation shall inspect the trench excavation to confirm soil conditions and installation procedures. For colder weather installation, all excavation, component placement and initial backfill should be performed in dry weather conditions and any segments of trenching should be substantially completed prior to any precipitation event. It is recommended that exposed chambers be backfilled as soon as possible to prevent any rainlsnow from accumulating in the open trenches. Terminal ends should be left exposed for final inspection by engineer. The installer shall photo document the installation of trench components prior to backfill of any trench segment. All septic system components and trench installations are to be approved by the Engineer prior to backfilling. Field Sizing: Receiving Wastewater Treatment Level 1; Soil type 2loading rate for a sandy silt loam is (0.6 gal./S.F./day).; Loading factors; (Table 10-2, pressured dosed trenches:0.8 ) and (Table 10-3, Chambers Category 3 = 0.7) A(sÐ Qd x L.F.l x L.F.2 . LTAR A: Area; LTAR: 0.6 Gal/S.F.lday for silt loam Qd: flow (gal/day):600 gpd L.F.1:0.8 full pressure dosed trenches Distribution L.F.2:0.7 Chambers Category 3 A(sÐ:600 epd x 0.8 x 0.7:560 S.F 0.6 Gal/S.F.iday Nurnber of Quick-4 Infi ltrator chambers 4' x3' x7 2" chambers : 560 S.F : 47 Infiltrator Quick-4 chambers; Use 52 chambers 12 S.F./Chamber Number of 5'x3' Bio-Diffuser chambers: 560 S.F :37 chambers; Use 42 chambers 15 S.F./Chamber STU Layout Use 72 Quick-4 Infiltrator chambers in four trenches 74'longby 3'wide with 18 chamber units per trench plus two end caps as delineated on the plan or equivalent Arc/Bio-Diffuser chamber trenches. The septic tank effluent will be pressure distributed to the head of each chamber trench via individual distribution pipes from an automatic distribution valve. Use 52 -Diffuser chambers in four trenches 54' long by 3'wide with 13 chambers units per trench plus two end caps as delineated on the plan or equivalent Bio-Diffuser chamber trenches. The septic tank effluent will be Lyndsay And Garret Jammaron Residence OWTS, TBD, Deer Park Court Glenwood Springs SE Job No. 32105.01 October 19,2022 Page4 pressure distributed to the head of each chamber row via individual distribution pipes from an ADU pressurized by a high head pump biotube discharge assembly in a the 500 gallon dosing tank. Effluent Distribution System The OWTS field shall be fully pressure dosed along the entire length of each trench. An Orenco Systems Bio Tube pump vault system will be installed with an effluent screen in the septic/dosing tank. The pump systern shall incorporate a single high head pump. The simplex pump assembly will demand dose effluent through a single 1.5- inch diameter PVC transport pipe frorn the pump assembly and connect to a two outlet ADU (Model 6402) valve housed in a ribbed PVC riser. The ADU must be installed with the inlet pipe at a high point relative to the discharge assembly outlet and the individual distribution pipe connections to the manifold pipe at the head of each zone set of paired trenches. The 1.5" discharge transpot't pipe shall be installed with a minimum 2.5Yo continuous slope to allow for drainage of the pipe back to the pump vault. The effluent will be alternately equally pressure dosed through each 1.S-inch custom perforated distribution lateral running the length of the trench installed on the absorptive surface centered below the chambers. The distribution laterals will have 5/16-inch orifices drilled every 2.0 feet oriented upward to spray against the interior chamber units. The first and last orifice will be drilled and oriented downward with an orifice shield to allow drainage of the line. Individual 1.5-inch ball valves will be installed at the end of each perforated distribution lateral centered below one of the end cap vertical inspection port penetratiorrs at tlte terntitral end of the field. A vertical 4-inch inspection port will be installed from an end cap inspection port penetration at the terminal end of each trench and one 4-inch inspection port will be installed from a end cap penetration at the head of each trench. All inspection ports shall extend a minimum 2-inches above the finish grade and be topped with a pipe cap. Pump operations shall be controlled by a pedestal mounted exterior control panel in close proximity with tlirect line of site with the tank. Automatic float switches for on, off and high water with alarm activation shall be installed on a dedicated PVC float tree. Two separate circuits from the electrical circuit panel and/or junction box shall be routed to the control panel for separate power to the controls and pump. Construction and Inspections Prior to construction of the permitted system, the engineer should be contacted by the contractor and owner to discuss the system components with the contractor, answer questions, resolve any conflict issues and schedule inspection site visits based on construction progress. A pre-OWTS construction meeting is essential and required prior to installation of the OWTS. All septic system components shall be staked in the field for approval by the Engineer prior to excavation. During construction the engineer will consult with installer regarding installation procedures and schedules, review photographs and attempt to perform timely inspections daily to allow for backfilling during cold weather conditions. All septic system componcnts and trench installations are to be approved by the Engineer prior to backfilling. All installation will be inspected, fîeld measured, reported and delineated in the Certification lcttcr and rccord drawing. The contractor nccds to photo document all OWTS construction phases and supply photos to the Engineer on a daily basis. County Regulations require that the Engineers of record perform site inspections of the permitted system during construction and provide "As-Builf' documentation of the installed system to the County after construction is complete. With respect to r":oltl weaúrer ancl/or winter cr:nditious efforts to allow county inspection of installed component prior to final backfill shall be coordinated to the extent possible. Lyndsay And Garret Jammaron Residence OWTS, TBD, Deer Park Court Glenwood Springs SE Job No. 32105.01 October 19,2022 Page5 OWS Oneration and Illaintenance Ownership of the system and responsibility for maintenance and repair will rernain with the property Owner. The Owner is encouraged to retain the servicçs of qualified personnel to inspect the OWTS dosing and distribution systems atrd to perform all maintenance and repairs necessary to ensure that the system components are maintained in good operating condition. The tanks and freld system should be inspected and maintained as needed. Suitable vegetative cover should be re-estabtished in the freld area, The components of the OWTS system should be inspected within 14 days of being placed into operation, again in early spring and thereafter should be inspected and maintained bi-annually. The tank, absorption field and other system components should be visually inspected bi- annually for debris, damage, leaks, or other potential problerns. In general, for a properly utilized system, septic tanks should be pumped every 3 - Syears. The effluent fìlter and pump fìoats should be cleaned every six months and at the tirne of tank pumping. Absorption fields should be maintained with suitable vegetative cover and kept free of root invasive plants. Positive surface drainage away from the absorption freld should be maintained. If you have any question or need any additional information, please call. Sincerely, SOPzuS ENGINEERING, LLC PaulË. Rutledge Design Engineer Principal '&t q7 2t¿? 28377