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HomeMy WebLinkAboutDesign Report 09.07.2019ALL SIRVIfI 33 Four Wheel Drive Rd Carbondale, CO 81623 970-309-5259 September 7, 2019 Project No. C1355 Roger Giard rgiard(a7rof.net Subsurface Investigation and Onsite Wastewater Treatment System Design 7 -Bedroom Residence Big Mountain Ranch TBD CR 230 Garfield County, Colorado Roger, ALL SERVICE septic, LLC performed a subsurface investigation and completed an onsite wastewater treatment system (OWTS) design for the subject residence. The 1000+ acre property is located outside of Rifle, in an area where OWTSs and wells are necessary. The original OWTS design dated February 19, 2018 was installed and inspected. The residence was still under construction. A change to the house plans includes an additional bedroom. There will be a total of 7 -bedrooms in the residence and therefore capacity must be added to the system to accommodate the additional bedroom. This design addressed the necessary addition to the OWTS. Legal Description: Section: 19 Township: 3 Range: 93 LOTS 1, 2, 3 AND 4, E1/2W1/2, W1/2E1/2, E1/2NE, SESE. SECTION 30: LOTS 1 & 2, E1/2NW, N1/2NE. TOWNSHIP 3: RANGE 94: SECTION 24: S1/2SW LYING EAST OF COUNTY ROAD 252, S1/2SE. SECTION 25: E1/2NW LYING EAST OF COUNTY ROAD 252, N1/2NE, SWNE. ALSO A TR. OF LAND CONT. 27 AC.+/- AS DESCRIBED IN RECEPTION #555469. EXCEPT A TR. OF LAND CONT. 27 AC.+/- AS DESCRIBED IN RECEPTION # 555470. EXCEPT A TR. OF LAND CONT. 40 AC.+/- AS DESCRIBED IN RECEPTION # 610789. PARCEL CAN NOT BE SOLD SEPARATELY FROM SIBLING ACCOUNT 1877-253-00-032. Parcel ID: 1877-251-00-029 SITE CONDITIONS A 7 -bedroom, single-family residence is presently under construction. There is a private well located north of the residence greater than 50 -feet from the proposed septic tank and greater than 100 -feet from the proposed soil treatment area (STA). The proposed STA location has an approximate 15% slope to the southwest. The proposed area is covered with native grasses. SUBSURFACE The subsurface was investigated on January 24, 2018 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.' ' 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 the Test Pit #1 consisted of dark brown clay loam with moderate structure grade and some cobbles to 6 -feet, underlain by medium to light brown clay loam with weak structure grade to a maximum depth explored of 8.0 -feet. No bedrock or groundwater was encountered. The materials encountered in the Test Pit #2 consisted of dark brown clay loam with moderate structure grade and some cobbles to 4 -feet, underlain by medium to light brown clay loam with weak structure grade to a maximum depth explored of 8.0 -feet. No bedrock or groundwater was encountered. A tactile analysis of the soils was taken from Test Pit #1 at 3 -feet below grade. The soil formed a ball and a ribbon approximately 1 to 2 -inches in diameter before breaking. The texture of the soil was both gritty and smooth. Soil structure shape was blocky, soil structure grade was moderate, and consistence was firm. Structure grade of the soil below 6 -feet in Test Pit #1 and below 4 -feet in Test Pit #2 was weak. STA sizing is based on Soil Type 3A, Clay Loam with weak structure grade. A long term acceptance rate (LTAR) of 0.3 gallons per square foot will be used to design the OWTS, in accordance with Table 10-1 Soil Type 3A presented in the Garfield County On -Site Wastewater Treatment System Regulations, adopted April 14, 2014. Weak Structure Grade below 6 -feet Sieved sample Page 3 Weak structure grade begins at 4 -feet in Test Pit #2 Backfill DESIGN SPECIFICATIONS Design Calculations: Average Design Flow = 75 GPD x 2 people/bedroom x 3 Bedrooms + 300 GPD (4th -7th bedrooms) = 750 GPD LTAR = 0.3 GPD/SF 750 GPD / 0.3 GPD/SF x 0.8 (pressure dosed trenches) x 0.7 (chambers) = 1400 SF The OWTS design is based on 7 -bedrooms. An average daily wastewater flow of 750 GPD will be used. A 4 -inch diameter SDR -35 sewer pipe with a double -sweep cleanout will be installed with a minimum 2% fall from the house to the septic tank. The system installation will include a 2000 -gallon, two-compartment Valley Precast concrete septic tank followed by a 500 -gallon, concrete pump chamber with an Orenco® ProPak pumping system and PF3005 pump. The floats must be set to dose approximately 80 gallons each pump cycle. Risers must be installed on the septic tank manholes to bring access to grade. Handle extensions on both the effluent filter and float tree must be installed if the riser height exceeds 1 -foot. The control panel must be located within line of sight of the septic tank. We recommend Valley Precast out of Buena Vista perform start up on the pumping system. A 1.5 -inch diameter Schedule 40 pump line must be installed from the pump to an Orenco® automatic distributing valve (ADV), model 6606. This pump line must have a minimum 1% grade for proper drain back into the tank after each pump cycle. The ADV must be placed a high point in the system and be placed in an insulated riser with access from grade. Screened rock must be placed below the ADV to support the ADV and to assure the clear pipes existing the ADV remain visible for future inspection and maintenance. Effluent will be pressure dosed through 1.5 -inch diameter pipes to six trenches, each with 20 `Quick 4' Low Profile Infiltrator® chambers, for a total of 120 chambers and 1440 square feet of infiltrative area. There must be at least 6 -feet of undisturbed soil between each trench. Shallow installation (between 1 and 3 -feet below grade) will allow the infiltrative area to be placed in the more moderate structure grade of the soil. Effluent will be pressure dosed to 1.5 -inch diameter laterals, which must be hung with zip ties from the underside of the chambers. Laterals will have 5/32 -inch diameter orifices facing up, with the exception of the first and last holes facing down for drainage. Orenco® Orifice Shields may be placed under each downward -facing orifice. The orifices must be drilled 3 -feet on center. Each lateral must end in a 90 Page 4 degree ell facing up with a ball valve for flushing. Valves may be placed in a valve box, accessible from grade, for access. Inspection ports must be placed at the beginning and end of each trench. Ports may be cut to grade and covered with a valve 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 STA. 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. 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. Page 5 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 ft Ccs.. Cs -f atA1-8 Carla Ostberg, MPH, REHS Reviewed By: 1