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Home My WebLink AboutOWTS Design129 Cains Lane Carbondale, CO 81623 970.309.5259 carla.ostberg@gmail.com September 7, 2021 Project No. C1652 Gary Manchester gmanchester@lastridgedev.com Subsurface Investigation and Onsite Wastewater Treatment System Design 5-Bedroom Residence Lot 26, Stirling Ranch Garfield County, Colorado Gary, CBO Inc. performed a subsurface investigation and completed an onsite wastewater treatment system (OWTS) design for the subject residence. The 9.642-acre property is located outside of Carbondale, in an area where OWTSs are necessary. Legal Description: Section: 29 Township: 7 Range: 87 Subdivision: STIRLING RANCH PUD Lot: 26 Parcel ID: 2391-293-05-026 SITE CONDITIONS The property is currently undeveloped. A 5-bedroom single-family residence is proposed. Potable water will be provided by a community water system. The water line will enter the property from the north and will not come within 25-feet of any OWTS component. The proposed STA location has an approximate 8% slope to the south. The proposed area is vegetated with native grasses, sage, pinion trees, and scrub oak. 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 September 2, 2021 by digging two soil profile test pit excavation (Test Pit). 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 topsoil to 18-inches, underlain by dense, light brown to tan calcareous clay matrix a maximum depth explored of 6.5-feet. No bedrock or groundwater was encountered. The materials encountered in Test Pit #2 consisted of dark brown topsoil to 18-inches, underlain by dense, light brown to tan calcareous clay matrix a maximum depth explored of 6.5-feet. No bedrock or groundwater was encountered. 1 Carla Ostberg holds a Certificate of Attendance and Examination from the CPOW Visual and Tactile Evaluation of Soils Training. Page 2 A sample of the soils was taken from Test Pit #1 at 3-feet below grade. Soil structure grade was weak (dense). The soil formed a ball and a ribbon less than 1-inch in length before breaking. Soil structure shape was blocky and consistence was friable to firm. Soil texture was both gritty and smooth. STA sizing is based on Soil Type 2A. A long term acceptance rate (LTAR) of 0.5 gallons per square foot will be used to design the OWTS. Test Pit #1 Backfill Sieved sample Ribbon less than 1-inch Page 3 Sidewall Test Pit #2 Backfill Digging Test Pit #2 DESIGN SPECIFICATIONS Design Calculations: Average Design Flow = 75 GPD x 2 people/bedroom x 3 Bedrooms + 150 GPD (4th and 5th bedrooms) = 600 GPD LTAR = 0.5 GPD/SF 600 GPD / 0.5 GPD/SF x 1.0 (gravity trenches) x 0.7 (GeoMat™) = 840 SF Page 4 The new OWTS design is based on 5-bedrooms in a single-family residence. An average daily wastewater flow of 600 GPD will be used. For the purposes of this OWTS design, Benchmark Elevation at grade 982’ has been established as 100’ at the main level finished floor. There will also be a lower level with finished floor at 970’ (88’). 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 47’ from LL FF / min 2% fall to septic tank / min. 11.75” fall Distribution Box Approximate horizontal distance 28’ / min. 1% fall to distribution box / min. 3.5” fall Infiltrative Surface Approximate horizontal distance to lowest trench 45’ / min. 1% fall / min. 5.625” *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 double-sweep clean out and a minimum 2% grade to the septic tank. There will be an additional sewer line serving the Master Bedroom Wing. This 4-inch diameter SDR-35 sewer line must also have a minimum 2% fall and tie into the residence sewer line with a “wye” fitting prior to the septic tank. The system installation must include a 1500-gallon, two-compartment septic tank (either concrete or poly) 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. Effluent will gravity flow to a distribution box, and then to five GeoMat™ 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 be 36-inches wide with 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. 39-inch wide GeoMat™ will be placed on top of the sand filter material the entire length of the 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 5 trenches, each with 56 linear feet of 39-inch wide GeoMat™ for a total of 280 linear feet and 840 sqaure feet. 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 5 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 # 1500T-2CP 1500-gallon, two-compartment concrete septic tank Biotube Effluent Filter Orenco® (2) Full Size Effluent Filters and housings Distribution Box PolyLok Distribution box, risers, lid, and flow equalizers (4) GeoMat™ GeoMatrix Systems, LLC 280 ‘GeoMat™ (39” wide sheets) 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 6 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 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 R008801 Par cel Number 239129305026 Acr es 10 Land SqFt 0 T ax Ar ea 011 2019 Mill Levy 75.5380 Physical Addr ess 0 SC HO O NER LN C ARBONDALE 81623 Owner Addr ess MANC HESTER, GARY P & JEANE M 1720 WAZEE #5D DENVER C O 80202 2019 T otal Actual Value $275,000 Last 2 Sa les Date Pr ice 8/19/2016 $275,000 4/30/2014 $225,000 Date created: 9/7/2021 Last Data Uploa ded: 9/7/2021 2:13:39 AM 921 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 9/7/2021 qPublic.net - Garfield County, CO - Property Record Card: R008801 https://qpublic.schneidercorp.com/Application.aspx?AppID=1038&LayerID=22381&PageTypeID=4&PageID=9447&KeyValue=R008801 1/2 Gareld County, CO View Map MANCHESTER, GARY P & JEANE M 1720 WAZEE #5D DENVER CO 80202 Assessed Year 2021 2020 2019 Land Actual $275,000.00 $275,000.00 $275,000.00 Improvement Actual $0.00 $0.00 $0.00 Total Actual $275,000.00 $275,000.00 $275,000.00 Assessed Year 2021 2020 2019 Land Assessed $79,750.00 $79,750.00 $79,750.00 Improvement Assessed $0.00 $0.00 $0.00 Total Assessed $79,750.00 $79,750.00 $79,750.00 Tax Year 2020 2019 2018 2017 Taxes Billed $6,024.16 $6,077.68 $5,482.96 $5,241.04 Click here to view the tax information for this parcel on the Gareld County Treasurer's website. Sale Date Deed Type Reception Number Book - Page Sale Price 8/19/2016 WARRANTY DEED 881301 $275,000 4/30/2014 WARRANTY DEED 848739 $225,000 6/15/2009 QUIT CLAIM DEED 769991 $0 7/31/2006 QUIT CLAIM DEED 705103 1835-0160 $0 5/14/2002 DECLARATION 603327 1354-672 $0 Summary Account R008801 Parcel 239129305026 Property Address 0 SCHOONER LN, CARBONDALE, CO 81623 Legal Description Section: 29 Township: 7 Range: 87 Subdivision: STIRLING RANCH PUD Lot: 26 Acres 9.642 Land SqFt 0 Tax Area 11 Mill Levy 75.5380 Subdivision STIRLING RANCH PUD Owner Land Unit Type VACANT RES LOTS - 0100 (VACANT LAND) Square Feet 0 Actual Values Assessed Values Tax History Transfers 9/7/2021 qPublic.net - Garfield County, CO - Property Record Card: R008801 https://qpublic.schneidercorp.com/Application.aspx?AppID=1038&LayerID=22381&PageTypeID=4&PageID=9447&KeyValue=R008801 2/2 5/13/2002 AGREEMENT 603326 1354-662 $0 1/15/2002 SPECIAL WARRANTY DEED 596038 1322-402 $0 1/15/2002 WARRANTY DEED 596037 1322-401 $0 7/3/2001 PERSONAL REP DEED 584536 1269-478 $0 7/7/2000 ARTICLES 609487 1380-289 $0 11/26/1999 LETTERS 558189 1169-631 $0 12/2/1985 Deeds 679-804 $0 1/1/1900 AFFIDAVIT 810-609 $0 1/1/1900 AFFIDAVIT 810-607 $0 1/1/1900 AFFIDAVIT 810-606 $0 1/1/1900 Deeds 635-813 $0 1/1/1900 Deeds 634-219-220 $0 1/1/1900 Deeds 574-304 $0 1/1/1900 Deeds 416-75 $0 1/1/1900 Deeds 307-380 $0 1/1/1900 PERSONAL REP DEED 1169-257 $0 1/1/1900 GENERAL WARRANTY DEED 1103-213 $0 No data available for the following modules: Buildings, Sketches. 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