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Home My WebLink AboutOWTS Design129 Cains Lane Carbondale, CO 81623 970.309.5259 carla.ostberg@gmail.com October 16, 2021 Project No. C1649 Matthew Ringer mmringer21@gmail.com Subsurface Investigation and Onsite Wastewater Treatment System Design 4-Bedroom Residence 7315 Garfield Creek Road Garfield County, Colorado Matthew, CBO Inc. performed a subsurface investigation and completed an onsite wastewater treatment system (OWTS) design for the subject residence. The 242.075-acre property is located outside of New Castle, in an area where OWTSs and wells are necessary. Legal Description: Section: 31 Township: 6 Range: 90 A TRACT OF LAND IN SECTIONS 31 AND 32 MORE PARTIULARLY DESCRIBED IN WD RECEPTION# 881149. 242.075 ACRES Parcel ID: 2183-322-00-011 SITE CONDITIONS The property is currently developed with a 2-bedroom cabin that is served by a separate OWTS. An additional 4-bedroom residence is proposed. The new residence will be located to the southwest of the existing cabin. A private well on the property is located to the northwest of both the existing cabin and proposed residence. The well is greater than 50-feet from the proposed septic tank and greater than 100-feet from the proposed soil treatment area (STA). The water line will come from the cabin to the northeast and will be at least 10-feet from the septic tank and at least 25-feet from the STA. The proposed STA location has an approximate ten percent slope to the north and northwest. The proposed area is 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. SUBSURFACE The subsurface was investigated on July 30, 2021 by digging three soil profile test pit excavations (Test Pits). A visual and tactile soil analysis was completed by Carla Ostberg at the time of excavation.1 1 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 #1 consisted of medium brown topsoil to 1.5-feet, underlain by reddish brown clay loam to a maximum depth explored of 6.0-feet. No bedrock or groundwater was encountered. The materials encountered in Test Pit #2 consisted of medium brown clay loam to a maximum depth explored of 6.0-feet. No bedrock or groundwater was encountered. The materials encountered in Test Pit #3 consisted of medium brown clay loam to a maximum depth explored of 6.0-feet. No bedrock or groundwater was encountered. A sample of the soils was taken from Test Pit #1 at 3-feet below grade. Soil structure grade was moderate. The soil formed a ball and a ribbon 1 to 2-inches in length before breaking. Soil structure shape was blocky, and consistence was firm. Soil texture was both gritty and smooth. STA sizing is based on Soil Type 3, Clay Loam with moderate structure grade. A long term acceptance rate (LTAR) of 0.35 gallons per square foot will be used to design the OWTS. Test Pit #1 Page 3 Sieved sample Ribbon length Test Pit #2 Page 4 Test Pit #2 View of Test Pits View of Test Pits DESIGN SPECIFICATIONS Design Calculations: Average Design Flow = 75 GPD x 2 people/bedroom x 3 Bedrooms + 75 GPD (4th Bedroom) = 525 GPD LTAR = 0.35 GPD/SF 525 GPD / 0.35 GPD/SF x 1.0 (gravity trenches) x 0.7 (GeoMat™) = 1050 SF The new OWTS design is based on 4-bedrooms. An average daily wastewater flow of 525 GPD will be used. Page 5 For the purposes of this OWTS design, Benchmark Elevation at grade 6832’ (Finished Floor Main Floor) has been established as 100’. The sewer line will exit the residence at approximately 98’. It should be noted there is a lower level in the residence with a Finished Floor elevation of approximately 6822’. An ejector pump(specifications will be utilized to raise wastewater from the lower level. Specifications and installation of the ejector will be provided by a plumbing contractor. 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 16’ / min. 2% fall / min. 4” fall Distribution Box Approximate horizontal distance 60’ / min. 1% fall / min. 7.5” fall Infiltrative Surface Approximate horizontal distance to furthest trench 40’ / min. 1% fall / min. 5” fall *Elevations are based upon standard OWTS installation practices. Component elevations may change during installation due to site conditions. The 4-inch diameter SDR-35 sewer line exiting the residence must have a double-sweep clean out and a minimum 2% grade to the septic tank. The system installation must include a minimum 1250-gallon, two-compartment concrete septic tank with an effluent filter on the outlet tee. Any state-approved poly septic tank may also be used. 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. Effluent will gravity flow to a distribution box, and then to six trenches, each 58.5-feet in length. 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 be 36-inches wide and a minimum of 6-inches of sand filter material placed in the trench. Sand filter material must be clean, coarse sand, all passing a screen having four meshes to the inch. The sand must have an effective size between 0.15 and 0.60 mm. The uniformity coefficient must be 7.0 or less. Material meeting ASTM 33, for concrete sand, with three percent or less fines passing 200 mesh sieve may be used. A gradation of the sand media must be submitted to this office prior to obtaining the sand. GeoMat™ will be placed on top of the sand filter material the entire length each trench. The GeoMat™ is 39-inches wide and may curl up the sides of the trenches slightly. A 4-inch diameter perforated pipe will be placed down the center of the GeoMat™, under the top layer of fabric. The STA will consist of a total of 351 linear feet of 39-inch wide GeoMat™. All material associated with the GeoMat™ installation must be proprietary products associated with the GeoMat™, including the geotextile fabric. Manufacturer instructions must be followed regarding installation of the GeoMat™. 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. The front inspection port will be placed to the side of the GeoMat™ and the end inspection port will be tied onto the end of the lateral. Ports may be cut to grade and placed in sprinkler boxes for access. There shall be no cobble-sized (<2.5”) or greater rock in final cover over the GeoMat™. 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 # 1250T-2CP 2-compartment concrete septic tank Effluent Filter Orenco® Full size 4-inch effluent filter Tank Risers and Lids Orenco® Double-walled PVC Risers and Lids (24” diameter) Distribution Box PolyLok D-Box 8C Poly distribution box, lids, risers, and flow equalizers GeoMat™ GeoMatrix Systems, LLC 351 ‘GeoMat™ (39”) 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 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. Carla Ostberg, MPH, REHS Garfield County, CO Developed by Account Number R017214 Par cel Number 218332200011 Acr es 242 Land SqFt 0 T ax Ar ea 017 2019 Mill Levy 56.1850 Physica l Addr ess 7315 C OUNTY 312 RD NEW C ASTLE 81647 Owner Addr ess RINGER, SYL VIA M & MATTHEW M 7315 C OUNTY ROAD 312 NEW C ASTLE C O 81647 2019 T otal Actual Value $285,640 Last 2 Sa les Date Pr ice 1/5/2021 $0 1/5/2021 $0 Date created: 10/16/2021 Last Data Uploa ded: 10/16/2021 2:04:03 AM 3,039 ft Overvi ew Legend Parcels Roa ds Parcel/Account Number s Highw ays Limited Access Highwa y Major Road Loca l Roa d Minor Road Other Road Ra mp Ferry Pedestria n Way Owner Na me Lakes & River s County Boundar y Line