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Home My WebLink AboutOWTS Design129 Cains Lane Carbondale, CO 81623 970.309.5259 carla.ostberg@gmail.com May 28, 2022 Project No. C1725 Travis Vickroy tvick78@icloud.com Subsurface Investigation and Onsite Wastewater Treatment System Design Barn 1708 CR 121 Garfield County, Colorado Travis, CBO Inc. performed a subsurface investigation and completed an onsite wastewater treatment system (OWTS) design for the subject residence. The 960.01-acre property is located outside of Glenwood Springs, in an area where OWTSs and wells are necessary. Legal Description: Section: 32 Township: 6 Range: 87 A PARCEL OF LAND SITUATE IN SECTIONS 28, 29, 32 & 33, SAID PARCEL BEING MORE PARTICULARLY DESCRIBED PER WARRANTY DEED RECEPTION NO. 944306 960.01 ACRES Parcel ID: 2189-322-00-033 SITE CONDITIONS A Barn is currently under construction on this portion of the property. There is a desire to add plumbing to the structure and size the OWTS to accommodate 2-bedrooms. The Barn will be served by a well located to the west of the structure. The well is greater than 50-feet from the proposed septic tank and greater than 100-feet from the proposed soil treatment area (STA). A ditch runs to the south of the Barn. The ditch is greater than 50-feet from the proposed STA. The proposed STA location has an approximate 14-15 percent slope to the south. The proposed area is in an open field, vegetated with native grasses. There should be no traffic or staging of material over the future STA site to avoid compaction of soils prior to construction of the STA. Page 2 SUBSURFACE The subsurface was investigated on May 19, 2022 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.1 The materials encountered in Test Pit #1 consisted of dark brown clay loam with moderate structure grade to 2.0-feet, underlain by reddish 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 Test Pit #2 consisted of dark brown clay loam with moderate structure grade to 4.0-feet, underlain by reddish brown clay loam with weak structure grade to a maximum depth explored of 8.0-feet. No bedrock or groundwater was encountered. A sample of the soils was taken from Test Pit #1 at 3-feet below grade. The soil formed a ball and a ribbon 1 to 2-inches in length before breaking. Soil structure shape was blocky and consistence was friable. Soil texture was both gritty and smooth. 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. View of Test Pit #1 location, looking north Test Pit #1 1 Carla Ostberg holds a Certificate of Attendance and Examination from the CPOW Visual and Tactile Evaluation of Soils Training. Page 3 Backfill Sieved sample Blocky peds Ribbon 1 to 2-inches in length Looking east Test Pit #2 Page 4 Backfill Weaker structure is deeper in Test Pit #2 Page 5 DESIGN SPECIFICATIONS Design Calculations: Average Design Flow = 75 GPD x 2 people/bedroom x 2 Bedrooms = 300 GPD LTAR = 0.3 GPD/SF 300 GPD / 0.3 GPD/SF x 1.0 (gravity trenches) x 0.7 (chambers) = 700 SF The new OWTS design is based on 2-bedrooms. An average daily wastewater flow of 300 GPD will be used. For the purposes of this OWTS design, Benchmark Elevation has been established as 100’ as the Finished Floor elevation of the Barn. CBO Inc. should be notified of any discrepancies or problems with grade elevations of proposed components during installation of the OWTS. OWTS Component Minimum Elevation Primary Tank Inlet Invert Approximate horizontal distance 45’ / min. 2% fall / min. 11.25” fall Distribution Box Approximate horizontal distance 80’ / min. 1% fall / min. 10” fall Infiltrative Surface Approximate horizontal distance to furthest trench 29’ / min. 1% fall / min. 3.625” fall *Elevations are based upon standard OWTS installation practices. Component elevations may change during installation due to site conditions. Minimum grade refers to piping between components. The 4-inch diameter Schedule 40 sewer line exiting the Barn must have a double-sweep clean out and a minimum 2% grade to the septic tank. The system installation must include a 1000-gallon, two-compartment Valley Precast concrete septic tank with an effluent filter on the outlet tee. Risers must bring the manhole lids to grade for access. If more than one riser is added to the septic tank, an extension handle must be installed on the effluent filter. The area to the east of the barn may be subject to traffic and we are recommending minimum Schedule 40 sewer line. If the septic tank will be subject to traffic, it must be traffic rated with cast iron manhole lids. Effluent will gravity flow to a distribution box, and then to three gravelless chamber trenches. The distribution box must be accessible from grade and must have flow equalizers, or similar product, installed on each outlet pipe in the distribution box to assure equal flow to each bed. Each trench will consist of 20 ‘Quick 4’ Standard Plus Infiltrator® chambers for a total of 720 square feet of infiltrative area. There must be at least 4-feet of undisturbed soil between each trench. Inspection ports must be installed at the beginning and end of each trench. Ports may be cut to grade and placed in sprinkler boxes for access. Page 6 COMPONENT SPECIFICATIONS The component manufacturers are typical of applications used by contractors and engineers in this area. CBO Inc. must approve alternative components prior to installation of the OWTS. Requests must be submitted, in writing, to our office for approval prior to installation. Component technical data sheets are available upon request. COMPONENT MANUFACTURER MODEL NO. COMMENTS Septic Tank Valley Precast Item # 1000T-2CP 1000-gallon, 2- compartment concrete septic tank Risers and Lids Orenco® Double-walled PVC risers and lids Effluent Filter Orenco® 4-inch diameter Full size Distribution Box Polylok Distribution box, lids, rises, and (3) flow equalizers Chambers Infiltrator® Standard Plus 60 ‘Quick 4’ chambers 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. INSTALLATION CONTRACTOR CBO Inc. expects that the installer be experienced and qualified to perform the scope of work outlined in this design. The installer must review this design thoroughly and coordinate with our office in advance of installation. Any additional conditions in this design or county permit must be completed and documented prior to final approval of the OWTS installation. Communication between the installer and this office is expected throughout the installation. INSTALLATION OBSERVATIONS CBO Inc. 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. CBO Inc. should be notified 48 hours in advance to observe the installation. In an effort to improve the accuracy of the record drawing, we request that the installer provide a sketch of the installation, including path of the sewer lines, water line installation (if applicable), septic tank location, STA location, and measurements from building corners or another fixed objects on the property. This sketch is most easily provided on Sheet W2.0 of the OWTS Design Packet. Photographs of the installation and final cover are also requested to supplement our installation documentation. 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 irrigation 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. Page 7 6-22-2022 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 the backfilled STA. Machines with tracks (not wheels) should be used during construction of the STA for better weight distribution. 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 the 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. LIMITS: The design is based on information submitted. If soil conditions encountered are different from conditions described in report, CBO Inc. 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, CBO Inc. Reviewed By: Carla Ostberg, MPH, REHS Romeo A. Baylosis, PE Garfield County, CO Developed by Account Number R084548 Par cel Number 218932200033 Acr es 960 Land SqFt 0 T ax Ar ea 011 2019 Mill Levy 79.7760 Physical Addr ess 0 GLENWOOD SPRINGS 81601 Ow ner Address SGJD L LC 75 ONEIDA DRIVE GREENWIC H C T 06830 2019 T otal Actua l Value $51,580 Last 2 Sales Date Price 6/7/2021 $0 5/20/2021 $0 Date created: 6/22/2022 Last Data Uploa ded: 6/22/2022 2:12:18 AM 6,078 ft Overvi ew Legend Parcels Roa ds Highw ays Limited Access Highwa y Major Road Loca l Roa d Minor Road Other Road Ra mp Ferry Pedestria n Way Lakes & River s County Boundar y Line