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Home My WebLink AboutOWTS Engineer's Design129 Cains Lane Carbondale, CO 81623 970.309.5259 carla.ostberg@gmail.com June 20, 2022 Project No. C1729 Kurt Carruth kurt@hinge-architects.com Subsurface Investigation and Onsite Wastewater Treatment System Design 4-Bedroom Residence + 1-Bedroom ADU 5011 CR 154 Garfield County, Colorado Kurt, CBO Inc. performed a subsurface investigation and completed an onsite wastewater treatment system (OWTS) design for the subject residence. The 1.35-acre property is located outside of Glenwood Springs, in an area where OWTSs and wells are necessary. Legal Description: Section: 1 Township: 7 Range: 89 Subdivision: ICE MINOR SUBDIVISION-AMENDED Lot: 3 1.35 ACRES Parcel ID: 2395-012-01-003 SITE CONDITIONS A 3-bedroom residence presently exists on the property. The residence is served by an existing OWTS. The existing OWTS consists of one 1250-gallon concrete septic tank followed by a soil treatment area (STA) comprised of a pipe and gravel seepage bed measuring 18’ x 45’ with 3’ of gravel under the perforated pipe. Individual Sewage Disposal System (ISDS) Permit 1348 documents this system. The permit received final approval on November 23, 1983. This system will be abandoned. A remodel to the residence is proposed which will result in 4-bedrooms in the residence and an attached 1-bedroom additional dwelling unit (ADU). The residence is served by a private well on the property. The well is greater than 50-feet from the proposed septic tank and greater than 100-feet from the proposed soil treatment area (STA). There is also a well on the neighboring property to the northwest. This well has been verified to be greater than 100-feet to the proposed OWTS components. The Roaring Fork River runs to the southwest of the residence. The OWTS components will be located greater than 50-feet from the edge of the river. The proposed STA location has an approximate five percent slope to the southwest toward the river. The area is 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 April 29, 2022 by digging one soil profile test pit excavation (Test Pit). A visual and tactile soil analysis was completed by Carla Ostberg at the time of excavation.1 Only one test pit was excavated in an effort not to disturb the existing STA. The materials encountered in Test Pit #1 consisted of reddish brown topsoil sandy loam to a maximum depth explored of 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. Soil structure grade was moderate. 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. Soil texture was gritty. STA sizing is based on Soil Type 2, Sandy Loam with moderate structure grade. Pressure-dosed, over- excavated, unlined sand filters with a minimum of 2-feet of sand filter material (Secondary Sand) are proposed. A long term acceptance rate (LTAR) of 0.8 gallons per square foot will be used to design the OWTS. DESIGN SPECIFICATIONS The existing septic tank will be abandoned by pumping the contents and crushing the top, bottom, and sides and filling the void with onsite material. If the existing STA is encountered during excavation for the new STA, any saturated soils will be over-excavated and staged for drying prior to disposal. Design Calculations: Average Design Flow = 75 GPD x 2 people/bedroom x 3 Bedrooms + 75 GPD (4th bedroom) + 150 GPD (1- Bedroom ADU) = 675 GPD LTAR = 0.8 GPD/SF (Base Soil Type 2, over-excavated sand filter) 675 GPD / 0.8 GPD/SF = 843.75 SF The new OWTS design is based on 4-bedrooms in the Main House and a 1-bedroom ADU. An average daily wastewater flow of 675 GPD will be used. For the purposes of this OWTS design, Benchmark Elevation has been established as 100’ as the existing sewer line that enters the existing septic tank. 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 6’ / min. 2% fall to septic tank / min. 1.5” fall Automatic Distributing Valve Approximate horizontal distance 40’ / min. 1% rise for drain back / min. 5” rise Infiltrative Surface Approximate horizontal distance 20’ / min. 1% fall to furthest bed / min. 2.5” 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 existing sewer line from the house to the existing septic tank will remain in use. We explored the sewer line with a camera, and it was found to be in good condition. 1 Carla Ostberg holds a Certificate of Attendance and Examination from the CPOW Visual and Tactile Evaluation of Soils Training. Page 3 A clean out should be installed in the existing sewer line and a new section of 4-inch diameter SDR-35 sewer line run to the new septic tank. The system installation will include a 1500-gallon, two-compartment Infiltrator® poly septic tank with an effluent filter on the outlet tee followed by a 500-gallon, single compartment Infiltrator® poly pump chamber with an Orenco® Biotube Pump Vault and an Orenco® PF3005 pump. 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 floats should be set to dose approximately 80 gallons each pump cycle, allowing approximately 4 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 Range Max = 172.75 gal. (675 GPD x 25% + 4 gal drain back) Min. 64 gal. (15 gal x 4) + 4 gal drain back Dose Setting 80 gallons/dose 4 gallons drain back (40’ / 1.5” diameter pump line) Float Separation 500 gallon single-compartment Infiltrator® poly pump chamber 6” on/off float separation Pump Criteria 28.5 gallons per minute (GPM) 25.2 feet total dynamic head (TDH) Effluent will be pumped through a 1.5-inch diameter pump line to an Orenco® automatic distributing valve (ADV), model 6402. 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 at a high point in the system 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 exiting the ADV remain visible for future inspection and maintenance. Effluent will be pressure dosed through 1.5-inch diameter distribution lines to two 10’ x 42.5’ beds. A minimum of 2-feet of sand filter material will be installed in the over-excavated footprints. 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. Laterals must be 1.5-inches in diameter with 5/32-inch diameter orifices facing down, spaced 3-feet on center, installed on the center of each GeoMat™ with the filter fabric over the laterals. Three 39” wide GeoMat™ sheets must be placed on each 10-foot wide bed. All material associated with the GeoMat™ installation must be proprietary products associated with the GeoMat™, including orifice shields and geotextile fabric. Manufacturer instructions must be followed regarding installation of the GeoMat™. Each 1.5-inch diameter lateral must end in a sweeping ell facing up with a ball valve for flushing. Valves should be placed in a 10-inch sprinkler box for access. Laterals must be covered by a soil separation fabric and at least 1-foot of topsoil or other suitable soil able to support vegetative growth. There shall be no cobble-sized (<2.5”) or greater rock in final cover over the GeoMat™. Inspection ports must be placed at each corner of each bed. Ports may be cut to grade and covered with a valve box for access. 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. Page 4 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 Tanks Infiltrator® 1530T-2CP 1500-gallon, two- compartment poly septic Effluent Filter Orenco® 4-inch full size filter Risers and Lids Orenco® Risers and Lids Pump Orenco® PF300511 ½ HP 120 Volt pump Biotube ProPak Pump Package Orenco® BPP30DD Vault, Filter, Panel (demand dose) Tank Risers and Lids Orenco® Double-walled PVC Risers and Lids (24” diameter) ADV Orenco® V6402A 1.5” Inlet and Outlets ADV Riser and Lid Orenco® Double-walled PVC Risers and Lids (30” diameter) GeoMat™ GeoMatrix Systems, LLC 243’ GeoMat™ (39” sheets) 78 orifice shields Flushing Assembly Orenco® 1.5” diameter (2) 45° or 90° long sweep only (6 total) 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. Page 5 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. 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. Page 6 7-18-2022 Please call with questions. Sincerely, CBO Inc. Reviewed By: Carla Ostberg, MPH, REHS Romeo A. Baylosis, PE Pump Selection for a Pressurized System - Single Family Residence Project Parameters Discharge Assembly Size Transport Length Before Valve Transport Pipe Class Transport Line Size Distributing Valve Model Transport Length After Valve Transport Pipe Class Transport Pipe Size Max Elevation Lift Manifold Length Manifold Pipe Class Manifold Pipe Size Number of Laterals per Cell Lateral Length Lateral Pipe Class Lateral Pipe Size Orifice Size Orifice Spacing Residual Head Flow Meter 'Add-on' Friction Losses 1.25 40 40 1.50 6402 20 40 1.50 5 6 40 1.50 6 40.5 40 1.50 5/32 3 5 None 0 inches feet inches feet inches feet feet inches feet inches inches feet feet inches feet Calculations Minimum Flow Rate per Orifice Number of Orifices per Zone Total Flow Rate per Zone Number of Laterals per Zone % Flow Differential 1st/Last Orifice Transport Velocity Before Valve Transport Velocity After Valve 0.68 42 28.5 3 0.8 4.5 4.5 gpm gpm % fps fps Frictional Head Losses Loss through Discharge Loss in Transport Before Valve Loss through Valve Loss in Transport after Valve Loss in Manifold Loss in Laterals Loss through Flowmeter 'Add-on' Friction Losses 5.7 1.9 6.5 0.9 0.1 0.1 0.0 0.0 feet feet feet feet feet feet feet feet Pipe Volumes Vol of Transport Line Before Valve Vol of Transport Line After Valve Vol of Manifold Vol of Laterals per Zone Total Vol Before Valve Total Vol After Valve 4.2 2.1 0.6 12.8 4.2 15.6 gals gals gals gals gals gals 28.5 25.2 gpm feet 0 5 10 15 20 25 30 35 400 50 100 150 200 250 300 Net Discharge (gpm) PumpData PF3005 High Head Effluent Pump 30 GPM, 1/2HP 115/230V 1Ø 60Hz, 200V 3Ø 60Hz PF3007 High Head Effluent Pump 30 GPM, 3/4HP 230V 1Ø 60Hz, 200/460V 3Ø 60Hz PF3010 High Head Effluent Pump 30 GPM, 1HP 230V 1Ø 60Hz, 200/460V 3Ø 60Hz PF3015 High Head Effluent Pump 30 GPM, 1-1/2HP 230V 1Ø 60Hz, 200/230/460V 3Ø 60Hz Legend System Curve: Pump Curve: Pump Optimal Range: Operating Point: Design Point: 5011 CR 154 Legend 5011 Co Rd 154 100 ft N ➤➤ N Garfield County, CO Developed by Account Number R011607 Par cel Number 239501201003 Acr es 1 Land SqFt 0 T ax Ar ea 011 2019 Mill Levy 79.7760 Physical Addr ess 5011 154 C OUNTY RD GLENWO O D SP RINGS 81601 Ow ner Address NIC KOL AY, C L IVE & NAO ISE 15818 RO SEVIEW LANE C YPRESS TX 774296703 2019 T otal A ctual Va lue $1,083,320 L ast 2 Sales Date Pr ice 1/2/2020 $1,074,000 6/4/1993 $0 Date created: 6/2/2022 Last Data Uploa ded: 6/2/2022 2:18:50 AM 230 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