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HomeMy WebLinkAboutEngineer's Design Report 02.28.2017ALL SIHYICE" epti ti February 28, 2017 Mike Patch mkpatch@outlook.com 33 Four Wheel drive Rd Carbondale, CO 81623 970-309-5259 Subsurface Investigation and Onsite Wastewater Treatment System Design Masonry Barn Renovation 531 CR 153 Garfield County, Colorado Mike, Project No. C1262 ALL SERVICE septic, LLC performed a subsurface investigation and completed an onsite wastewater treatment system (OWTS) design for the subject 732 -acre property located outside of Carbondale, in an area where OWTSs and wells are necessary. Legal Description: Section: 12 Township: 8 Range: 88 A TR IN SEC 2, 11 & 12 Parcel ID: 2463-122-00-027 SITE CONDITIONS A masonry barn presently exists on the property. A remodel is planned for the structure which will result in a "country kitchen" with bathrooms, storage, and cooler space for family gatherings and fall canning of jams and jellies. Food preparation in the "country kitchen" is intended for family gatherings and is not anticipated to generate significant amounts of grease. There is currently no plumbing in the existing structure. The structure will be served by a private well located to the west of the subject structure. The well will be located at least 50 -feet from the proposed septic tank and at least 100 -feet from the proposed soil treatment area (STA). The proposed STA location slopes at approximately 7% to the south. The proposed trenches will run north and south; therefore, this area will be regraded in a way to promote proper drainage and accommodate appropriate cover over the trenches. The existing road to the north and east of the proposed STA will be realigned. The proposed STA is currently vegetated with native grasses. SUBSURFACE The subsurface was investigated on November 16, 2016 by digging two soil profile test pit excavations (Test Pits). A visual and tactile soil analysis was completed by Carla Ostberg at the time of excavation.' The materials encountered in Test Pit #1 consisted of medium brown, moist topsoil to 2 -feet, underlain by medium brown loamy sand with greater than 35% rock to 6 -feet, underlain by medium brown, loamy sand with less than 35% rock to a maximum depth explored of 10 -feet. No bedrock or groundwater was encountered. ' Carla Ostberg holds a Certificate of Attendance and Examination from the CPOW Visual and Tactile Evaluation of Soils Training. Page 2 The materials encountered in Test Pit #2 consisted of tan, dense caliche to 2 -feet, underlain by medium brown loamy sand with greater than 35% rock to 6 -feet, underlain by medium brown, loamy sand with less than 35% rock to a maximum depth explored of 8 -feet. No bedrock or groundwater was encountered. While the infiltrative area will be placed in what is classified as Soil Type 0 due to the percentage of rock content, the material below 6 -feet consists of the minimum required 4 -feet of suitable soil (Soil Type 1, Loamy Sand). Installation in the Soil Type 0 horizon is required in order to maintain shallow burial depth. Additionally, grade in the proposed STA may be changed to reduce the depth to the suitable soil horizon. A sample of the soils was taken from Test Pit #1 at 8 -feet below grade. The soil formed a ball but did not form a ribbon. Soil structure shape was single -grain to blocky, soil structure grade was loose to moderate, and consistence was loose. The soil texture was gritty. STA sizing is based on Soil Type 1, Loamy Sand. A long term acceptance rate (LTAR) of 0.8 gallons per square foot will be used to design the OWTS, in accordance with Table 10-1 Soil Type 1 presented in the Garfield County On -Site Wastewater Treatment System Regulations, adopted April 14, 2014. Topsoil to 2 -feet Rocky material from 2 to 6 -feet Sieved sample from 8 -feet below grade Test Pit #2 Page 3 Caliche in the first 2 -feet Similar rocky material from 2 to 6 -feet Material below 6 -feet is loamy sand with minimal rock (<35%) DESIGN SPECIFICATIONS The system was designed to accommodate an average daily wastewater flow of 300 gallons per day (GPD). We recommend metering water usage in the structure to assure future flows do not exceed 300 GPD. Additionally, the septic tank must be monitored for signs of grease during routine maintenance. If evidence of excessive amounts of grease is observed, actions should be taken to minimize grease from entering the OWTS, such as a change of practices in the kitchen and/or installation of a grease interceptor. This design is not intended to accommodate a commercial kitchen. Design Calculations: Average Design Flow = 300 GPD LTAR = 0.8 GPD/SF 300 GPD / 0.8 GPD/SF x 1.0 (gravity trenches) x 0.7 (chambers) = 263 SF 263 SF / 12 SF/ `Quick 4' chamber = min. 22 `Quick 4' Infiltrator® chambers A new 4 -inch diameter sewer line with a double -sweep clean out must be installed within 5 -feet of the structure. The sewer line must have a minimum 2% fall from the structure to the septic tank. Page 4 The system installation will include a new 1000 -gallon, two-compartment concrete septic tank with an Orenco® Biotube Effluent Filter on the outlet tee. The sewer line exiting the septic tank must be a 4 -inch diameter sewer line (minimum Schedule 40 if any portion runs under a driveway). This sewer line must have a minimum 1% fall. A distribution box, accessible from grade, must be installed. Flow equalizers, or similar product, must be installed to assure equal distribution to each trench. The new STA will consist of two rows of 11 `Quick 4' Infiltrator® chambers, for a total of 264 square feet of infiltrative area. The infiltrative area must be installed no less than 2 -feet and may not exceed 4 -feet below final grade. Trenches must be separated by at least 6 -feet of undisturbed soil. Inspection ports must be installed at both the beginning and end of each trench. Inspection ports may be cut to grade and covered with a sprinkler box for access. The component manufacturers are typical of applications used by contractors and engineers in this area. Alternatives may be considered or recommended by contacting our office. Construction must be according to Garfield County On -Site Wastewater Treatment System Regulations, the OWTS Permit provided by Garfield County Building Department, and this design. REVEGETATION REQUIREMENTS An adequate layer of good quality topsoil capable of supporting revegetation shall be placed over the entire disturbed area of the OWTS installation. A mixture of native grass seed that has good soil stabilizing characteristics (but without taproots), provides a maximum transpiration rate, and competes well with successional species. No trees or shrubs, or any vegetation requiring regular irritation shall be placed over the STA. Until vegetation is reestablished, erosion and sediment control measures shall be implemented and maintained on site. The owner of the OWTS shall be responsible for maintaining proper vegetation cover. OPERATION INFORMATION AND MAINTENANCE The property owner shall be responsible for the operation and maintenance of each OWTS servicing the property. The property owner is responsible for maintaining service contracts for manufactured units, alternating STAs, and any other components needing maintenance. Geo -fabrics or plastics should not be used over the absorption area. No heavy equipment, machinery, or materials should be placed on backfilled STAs. Livestock should not graze on the STA. Plumbing fixtures should be checked to ensure that no additional water is being discharged to OWTS. For example, a running toilet or leaky faucet can discharge hundreds of gallons of water a day and harm a STA. If an effluent filter or screen has been installed in the OWTS, we recommend this filter or screen be cleaned annually, or as needed. If the OWTS consists of a pressurized pump system, we recommend the laterals be flushed annually, or as needed. The homeowner should pump the septic tank every two years, or as needed gauged by measurement of solids in the tank. Garbage disposal use should be minimized, and non -biodegradable materials should not be placed into the OWTS. Grease should not be placed in household drains. Loading from a water softener should not be discharged into the OWTS. No hazardous wastes should be directed into the OWTS. Mechanical room drains should not discharge into the OWTS. The OWTS is engineered for domestic waste only. Page 5 ADDITIONAL CONSTRUCTION NOTES If design includes a pump, weep holes must be installed to allow pump lines to drain to minimize risk of freezing. The pump shall have an audible and visual alarm notification in the event of excessively high water conditions and shall be connected to a control breaker separate from the high water alarm breaker and from any other control system circuits. The pump system shall have a switch so the pump can be manually operated. Excavation equipment must not drive in excavation of the STA due to the potential to compact soil. Extensions should be placed on all septic tank components to allow access to them from existing grade. Backfill over the STA must be uniform and granular with no material greater than minus 3 -inch. INSTALLATION OBSERVATIONS ALL SERVICE septic, LLC must view the OWTS during construction. The OWTS observation should be performed before backfill, after placement of OWTS components. Septic tanks, distribution devices, pumps, dosing siphons, and other plumbing, as applicable, must also be observed. ALL SERVICE septic, LLC should be notified 48 hours in advance to observe the installation. LIMITS: The design is based on information submitted. If soil conditions encountered are different from conditions described in report, ALL SERVICE septic, LLC should be notified. All OWTS construction must be according to the county regulations. Requirements not specified in this report must follow applicable county regulations. The contractor should have documented and demonstrated knowledge of the requirements and regulations of the county in which they are working. Licensing of Systems Contractors may be required by county regulation. Please call with questions. Sincerely, ALL SERVICE septic, LLC Oak (E),_ Ov-ilukL8 Carla Ostberg, MPH, REHS Reviewed By: