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Home My WebLink AboutOWTS Design 09.25.2022129 Cains Lane Carbondale, CO 81623 970.309.5259 carla.ostberg@gmail.com September 25, 2022 Project No. C1735 Stig Svedberg ssvedberg@comcast.net Subsurface Investigation and Onsite Wastewater Treatment System Design 1-Bedroom Cabin 277 JB Court Garfield County, Colorado Stig, CBO Inc. performed a subsurface investigation and completed an onsite wastewater treatment system (OWTS) design for the subject residence. The 2.766-acre property is located outside of Glenwood Springs, in an area where OWTSs and wells are necessary. Legal Description: Quarter: SW Section: 25 Township: 5 Range: 90 A TR CONT 2.50 AC, ALSO A TR CONT. .22 AC. ALSO A TRACT OF LAND CONT. .046 AC.+/- AS DESC. IN RECEPTION # 858415. Parcel ID: 2123-253-00-046 SITE CONDITIONS There are two residences developed on the property: a 2-bedroom residence and a 1-bedroom cabin. Garfield County Assessor’s website notes the 2-bedroom residence was built in 1969 and the 1-bedroom cabin in 1971. Both are served by separate existing OWTSs. The OWTS serving the 2-bedroom residence was recently replaced under Garfield County Permit SEPT-7541. The subject OWTS serving the 1-bedroom cabin consists of an ejector pump in a chamber near the cabin which pumps wastewater to a single-compartment Roth® poly septic tank and gravity flows to a soil treatment area (STA). This system will be replaced. Potable water on the property is served by an existing well. The well is located to the south of the 2- bedroom residence. Canyon Creek runs to the west of the residences within the western property boundary. The proposed septic tank location will be within the 50-foot setback to the creek, but not closer than the existing ejector chamber 1. There is also an irrigation and ditch and pond to the east of the proposed STA that is filled with irrigation water during the summer months. The proposed STA will be located at least 50-feet from the irrigation 1 Garfield County On-Site Wastewater Treatment System Regulations, Table 7-1, Note: states “For repair or upgrading of existing OWTS where the size of lot precludes adherence to these distances, a repaired OWTS must not be closer to setback features than the existing OWTS, as reviewed and approved by the local public health agency.” Page 2 ditch and pond. It should be noted that the pond may require mitigation to assure there is no over- flow when it is full as the proposed STA is downgradient of the pond and there is evidence that over-flow has occurred in the past. Photo of pond The proposed STA location has an approximate five percent slope to the west toward Canyon Creek. The proposed area is vegetated with native grasses and is in the same approximate location as the existing STA, west of the recently replaced STA serving the 2-bedroom residence. 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 March 16, 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.2 The materials encountered in Test Pit #1 consisted of dark brown topsoil to 2.5-feet, underlain by medium brown to silty clay loam a maximum depth explored of 6.0-feet with increasing density below 5.5-feet. No bedrock or groundwater was encountered. The materials encountered in Test Pit #2 consisted of dark brown topsoil to 2.5-feet, underlain by medium brown to silty clay loam a maximum depth explored of 7.0-feet with increasing density below 6.5-feet. No bedrock or groundwater was encountered. A sample of the soil 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 firm to extremely firm. Soil texture was more smooth than gritty. Soil structure grade was moderate, becoming more dense with depth. A shallow (approx. 2-feet below native grade) installation of the STA is proposed. STA sizing is based on Soil Type 3, Silty 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. 2 Carla Ostberg holds a Certificate of Attendance and Examination from the CPOW Visual and Tactile Evaluation of Soils Training. Page 3 Test Pit #1 Sieved sample Ribbon length Page 4 Test Pit #2 View of Test Pit #2 looking toward Test Pit #1 (looking south) DESIGN SPECIFICATIONS The existing ejector chamber will be removed. The existing septic tank will also be abandoned by pumping and either removing or filling the void with onsite material. The existing STA will be abandoned in place. Design Calculations: Average Design Flow = 75 GPD x 1 people/bedroom x 2 Bedrooms = 150 GPD LTAR = 0.35 GPD/SF 150 GPD / 0.35 GPD/SF x 1.0 (pressured dosed bed) x 0.7 (chambers) = 300 SF Page 5 The OWTS design is based on 1-bedroom 3. An average daily wastewater flow of 150 GPD will be used. For the purposes of this OWTS design, Benchmark Elevation has been established as 100’ as the elevation of the existing sewer line exiting the cabin. 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 15’ / min. 2% fall / min. 3.75” fall Infiltrative Surface Approximate horizontal distance 114’ / min. 1% rise / min. 14.25” rise *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 sewer line exiting the cabin must be replaced with minimum 4-inch diameter SDR-35 sewer line with a double-sweep clean out and minimum 2% grade to the septic tank. The system installation will include a 1000-gallon, two-compartment Infiltrator® poly septic tank with an Orenco® Biotube Effluent Filter followed by a 500-gallon, Infiltrator® poly single-compartment with an Orenco® Biotube Pump Vault and an Orenco® PF3005 pump. The floats should be set to dose approximately 60 gallons each pump cycle, allowing approximately 12 gallons of drain back after each pump cycle. A pump curve is enclosed. The control panel for the pump must be located within line of sight of the septic tank. We recommend Valley Precast out of Buena Vista be contracted for start-up of the pumping system. Pump Table Dose Setting 60 gallons/dose 12 gallons drain back (114’ / 1.5” diameter pump line) Float Separation 500-gallon single-compartment Infiltrator® poly pump chamber 4.5” on/off float separation Pump Criteria 24.4 gallons per minute (GPM) 28.5 feet total dynamic head (TDH) A 1.5-inch diameter Schedule 40 pump line must be installed from the pump to the manifold connecting the laterals in the STA. This pump line must have a minimum 1% grade for proper drain back into the tank after each pump cycle. The pump line should connect to the manifold at a high point of the system to assure proper drain back after each pump cycle. Effluent will be pressure dosed to a gravelless chamber bed with two rows of 13 ‘Quick 4’ Standard Plus Low Profile Infiltrator® chambers, for a total of 26 chambers and 312 square feet of infiltrative area. A level 1.5-inch diameter manifold will connect 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 placed 3-feet on center. Each lateral must end in a 90 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. 3 Garfield County On-Site Wastewater Treatment System Regulations 43.6 A. 2. c. “…The minimum design flow for the repair or replacement of an OWTS of an existing one-bedroom home must be for one- bedroom unless bedrooms are added.” Page 6 The STA must be shallow, with burial depth of the chambers not to exceed 2-feet below native grade. 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 Infiltrator® IM 1060-2CP 1000-gallon, 2- compartment poly septic tank Effluent Filter Orenco® 4-inch diameter effluent filter (Full Size) Pump Chamber Infiltrator® IM 540-HH 500-gallon, single- compartment poly pump chamber Pump Orenco® PF300511 ½ HP 120 Volt Biotube ProPak Pump Package Orenco® BPP30DD Vault, Filter, Control Panel (demand dose) Tank Risers and Lids Orenco® Double-walled PVC Risers and Lids (24” diameter) Chambers Infiltrator® Plus Standard Low Profile 26 chambers Orifice Shields Orenco® 4 orifice shields Flushing Assembly Orenco® 1.5” diameter (2) 45° or 90° long sweep only (2 total) 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 Page 7 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. 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. Page 8 10-9__-__- 2022 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 R040303 Par cel Number 212325300046 Acr es 3 Land SqFt 0 T ax Ar ea 123 2019 Mill Levy 79.4730 Physical Addr ess 277 JB C T GL ENWOOD SPRINGS 81601 Owner Addr ess SVEDBERG, DAWN L INDA & STIG L ENNART 218 C O NTESSA C OURT L AFAYETTE C A 94549 2019 T ota l Actual Value $688,170 L ast 2 Sales Date Pr ice 9/7/2021 $0 9/2/2021 $853,000 Date created: 3/7/2022 Last Data Uploa ded: 3/7/2022 2:03:27 AM 460 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