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HomeMy WebLinkAboutEngineer's OWTS Design Packet-Revised129 Cains Lane Carbondale, CO 81623 970.309.5259 carla.ostberg@gmail.com May 21, 2025 Project No. C1942 Drew Taylor drewmt22@gmail.com Onsite Wastewater Treatment System Design 3-Bedroom Residence + 2-Bedroom Accessory Dwelling Unit (ADU) 310 Flying Fish Road Garfield County, Colorado Drew, CBO Inc. completed a onsite wastewater treatment system (OWTS) design for the subject residence. The 2.0-acre property is located outside of Carbondale, in an area where OWTSs and wells are necessary. A design outlining replacement of the septic tank is dated March 20, 2025. This design should be used in conjunction with those design details. Legal Description: Section: 32 Township: 7 Range: 87 A TR IN LOT 19 2 ACRES Parcel ID: 2391-322-00-032 SITE CONDITIONS The property is currently developed with a 3-bedroom residence and Accessory Dwelling Unit (ADU). The residences are served by an existing OWTS. The permit (enclosed) was provided by Garfield County Community Development Department. The subject OWTS consists of one 1000-gallon, two- compartment concrete septic tank followed by a soil treatment area (STA) comprised of a 50’ x 50’ lined Evaporation Transpiration (ET) bed. Individual Sewage Disposal System (ISDS) Permit 1383 documents the system. The system was sized to accommodate 3 bedrooms. The permit received final approval on December 14, 1984. The residences are served by a private well located in the west central portion of the property. The proposed STA will parallel the property line to the south and road to the east. The infiltrative area must be at least 10-feet from the property line and the toe of the slope must extend at a minimum 3:1 (horizontal: vertical) so the layout must accommodate the toe of the slope not extending past the property line to the south. SUBSURFACE The subsurface was investigated on March 13, 2205 by digging one soil profile test pit excavations (Test Pits). A visual and tactile soil analysis was completed by Carla Ostberg.1 The materials encountered in Test Pit #1 consisted of moist, dark brown loamy topsoil to 3.0-feet, underlain 1 Carla Ostberg holds a Certificate of Attendance and Examination from the CPOW Visual and Tactile Evaluation of Soils Training. Page 2 by sand and cobbles to a maximum depth explored of 5.0-feet where groundwater was encountered. Mottling was observed at approximately 2.0-feet below grade. The proposed STA will be a pressure-dosed, mounded, unlined sand filter with a minimum 3-feet of sand filter material (Secondary Sand) placed no more than 2-feet below native grade. A long term acceptance rate (LTAR) of 0.8 gallons per square foot will be used to design the OWTS. Test Pit #1 Page 3 Groundwater at 5’ Mottling observed at 2’ DESIGN SPECIFICATIONS The existing septic tank will be abandoned by pumping the tank and removing it or crushing the top, bottom, and sides and filling in the voids with onsite materials. We recommend removal of the septic tank due to the presence of high seasonal groundwater on the property. Specifications for the septic tank replacement have been outlined in a previous design dated March 20, 2025, but are included in this design in case upgrade of the entire OWTS will happen at one time. The existing STA will also be abandoned. There may be a liner under the existing STA, and this must be removed in the area of the new, mounded STA. Design Calculations: Average Design Flow = 75 GPD x 2 people/bedroom x 3 Bedrooms + 300 GPD (2 Bedroom ADU) = 750 GPD LTAR = 0.8 GPD/SF 750 GPD / 0.8 GPD/SF = 937.5 SF The OWTS design is based on 3-bedrooms in the residence and 2-bedrooms ADU. An average daily wastewater flow of 750 GPD will be used. For the purposes of this OWTS design, Benchmark Elevation has been established as 100’ as the existing sewer lines on the north side of the residence. An additional sewer line exits the residence near the entry. A sewer line also exits the south side of the ADU. Elevations of the existing septic tank inlet and outlet should be match for proper tie into the existing sewer lines and STA. CBO Inc. should be notified of any discrepancies or problems with grade elevations of proposed components during installation of the OWTS. Page 4 OWTS Component Minimum Elevation Primary Tank Inlet Invert Approximate horizontal distance from northern- most sewer line exiting the residence 64’ / min. 2% fall / min. 16” fall Automatic Distributing Valve (ADV) Approximate horizontal distance 65’ / min. 1% rise / min. 8.125” rise Infiltrative Surface Approximate horizontal distance 6’ / min. 1% fall / min. 0.75” fall The 4-inch SDR-35 sewer lines exiting the residence must have a double-sweep clean out and a minimum 2% grade to the septic tank. The system installation will include a 1500-gallon, two-compartment Infiltrator® poly septic tank with an Orenco® Biotube Effluent Filter on the outlet tee of the septic tank followed by a 500-gallon, single- compartment Infiltrator® poly pump chamber with an Orenco® Biotube Pump Vault and Orenco® PF3005 pump. Any state-approved concrete or poly septic tank and pump chamber may be substituted. Anchoring the septic tank and/or pump chamber with Deadmen because of the high seasonal groundwater table may be necessary. Risers must bring access to all manhole lids to grade. The floats should be set to dose approximately 85 gallons each pump cycle, allowing approximately 7 gallons of drain back. The control panel for the pump must be located within line of sight of the pump chamber. An electrician will be responsible for wiring the pumping system and the contractor will be responsible for connecting the plumbing. This office should be contacted for start-up of the system to verify its functioning and to perform a squirt test prior to use of the system. Pump Table Dose Range Max = 194.5 gal. (750 GPD x 25% + 7 gal drain back) Min. 69 gal. (15.5 gal x 4) + 7 gal drain back Dose Setting 85 gallons/dose 7 gallons drain back (65’ / 1.5” diameter pump line) Float Separation 500 gallon single-compartment Infiltrator® poly pump chamber 6.5” on/off float separation Pump Criteria 32.6 gallons per minute (GPM) 28.8 feet total dynamic head (TDH) Effluent will be pumped through a 1.5-inch diameter pump line from the pump chamber 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. The STA will consist of two 10’ x 47’ mounded, unlined sand filters. The excavation for the sand filter will begin 2.0-foot below native grade. A minimum of 3-feet of sand filter material will be installed in the over- excavated footprint, resulting in 1-foot of sand filter material extending above native grade. 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 provided. Laterals must be 1.5-inches in diameter with 5/32-inch diameter orifices facing down, spaced 3-feet on center, installed on the GeoMat™ with the filter fabric over the laterals. Laterals should be placed 2-feet from the edges of the bed with 3.0-feet between the laterals. Laterals will be connected with 1.5-inch diameter level manifolds. Three 39” wide GeoMat™ sheets must be placed on the 10-foot wide bed. All Page 5 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 the gray 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. The mound must have a minimum 3:1 slope (horizontal:vertical); therefore, the basal area will extend approximately 7.5-feet beyond the sand filter on all sides (with a mound height of approximately 2.5-feet above native grade). Soils in the sloped perimeter areas of the mound must be well draining and able to support vegetative growth. This soil must be approved by this office prior to installation. The mound must be crowned in a manner to promote drainage off the STA. 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 Effluent Filter Pump Chamber Infiltrator® Orenco® Infiltrator® IM-1530-2CP 4-inch diameter IM-500-1CP-HH 1500-gallon, two- compartment septic tank Full size 500-gallon, single- compartment pump chamber with HH pump 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) ADV Orenco® V6402A 1.5” Inlet and Outlets ADV Riser and Lid Orenco® Double-walled PVC Risers and Lids (30” diameter) Flushing Assembly Orenco® 1.5” diameter (2) 45° or 90° long sweep only (6 total) GeoMat™ GeoMatrix Systems, LLC 39” wide sheets 282’ GeoMat™ and 84 orifice shields Construction must be according to the jurisdiction’s adopted On-Site Wastewater Treatment System Regulations, the OWTS Permit, and this design. Page 6 PERMIT APPLICATION INSTRUCTIONS An OWTS Permit Application must be submitted to Garfield County Environmental Health Department. https://www.garfield-county.com/environmental-health/filesgcco/sites/16/OWTS-Application-Complete- Packet-Dec.-2019.pdf. We encourage communication with Garfield County Environmental Health to determine proper permitting protocol to implement the near-term STA replacement. All questions regarding permit submission can be directed to Garfield County Environmental Health Department, 970-945-6614 x8150. 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. 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. Page 7 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 Pump Selection for a Pressurized System - Single Family Residence Project 130 Flying Fish 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 65 40 1.50 6402 6 40 1.50 4 6 40 1.50 6 45 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 48 32.6 3 1.2 5.2 5.2 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 7.4 3.9 7.8 0.4 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 6.9 0.6 0.6 14.3 6.9 15.5 gals gals gals gals gals gals 32.6 28.8 gpm feet 0 5 10 15 20 25 30 35 40 0 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: o Q. di . J GARFIELD COUNTY BUILDING AND SANIY'AYION DEPARTMENT 44' •2014 Blake Avenue Glenwood Springs, Colorado 81601 Phone (303) 945-8241 This does not constitute INDIVID /AL SEWAGE DISPOSAL PERMIT p."1383 a building or use permit. Owner Peter H. Obuhanick System Location Hwy 8? Gov 't lute 19 R 10 Scfa 3? T7S RR7W Licensed Installer Owner Conditional Construction approval is hereby granted for a 1 0 gallon a(.X- _ Septic Tank or Aerated treatment unit. Absorption area (or dispersal area) computed as follows: Perc rate of one inch in if/ /i¢ minutes requires a minimum of N.fJ- sq. ft'. of absorption area per bedroom. Therefore the no. of bedrooms 3 x sq. ft. minimum requirement = a total of sq. ft. of absorption area. 4L ^- i9-X/5 'fl-.O ... e # --fj e.51/41_4s. e.51/41_4s. 5 5 'C// 'in, 6 5 =7.%' May we suggest .9 .: oc-t a'rre -- V "" L 8- i97aaic'n ,)c e 7) r -f - _s , v-rte Date 2 ray Inspector f'. /J /yC v.-) FINAL APPROVAL OF SYSTEM: No system shall be deemed to be in compliance with the Sewage Disposal Laws until the assembled system is approved prior to cover-ing any part. rfSnc • j SepticlTank access for inspection and cleaning within 12" of ground surface or aerated access ports above grouIsurface. tQ Proper materials and assembly.4'a J c . • Oeilfitf to rein* ,/re es e- /414, - C/O/C Trade name of septic tank or aerated treatment unit,cr ov " - / e 7 O/Cyirgs/y/Cale Adequate absorption (or dispersal) area. j U / 0 `\ - Adequate compliance with permit requirements.Lea et- ran C7cf 7r-.. t n r , vg o v q 1 Adequate cornpliance with County and State regulations /requirements.72- i IYLI--t: s " - " --------- Other Date t/ 54 Inspector Vii Jai a„ -a RETAIN WITH RECEIPT RECORDS AONSTRUCTION SITE CONDITIONS: 1. All installation must comply with all requirements of the County Individual Sewage Disposal Regulations, adopted pursuant to au- thority granted in 66-44-4, CRS 1963, amended 66-3-14, CRS 1963. 2. This permit is valid only for connection to structures which have fully complied .with County zoning and building requirements. Connection to or use with any dwelling or structures not approved by the Building and Zoning office shall automatically be a viola- tion of a requirement of the permit and cause for both legal action and revocation of the permit. 3. Section 111, 3.24 requires any person who constructs, alters, or installs an individual sewage disposal system in a manner which in• voives a knowing and material variation from the terms or specifications contained in the application of permit commits a Class I, Petty Offense (5500.00 fine - 6 months in jail or both). Applicant: Green Copy Department: Pink Copy SOIL_PERCOLATION TEST RESULTS: (To be completed by Registered Professional Engineer.) r Minutes per inch in hole No. 1 Minutes per inch in hole No. 3 Minutes per inch in hole No. 2 Minutes per inch in hole No._ Nance, address and telephone of RPE who made soil absorption tests: Name, address and telephone of RPE responsible for design of the system: Applicant acknowledges that the completeness of the application is conditional upon such further mandatory and additional tests and reports as may be required by the local health department to be made and furnished by the applicant or by the local health department for purposes of the evaluation of the application; and the issuance of the permit is subject to such terms and conditions as deemed necessary to insure compliance with rules and regulations adopted under Article 10, Title 25, C.R.S. 1973, as amended. The undersigned hereby certifies that all statements made, information and reports submitted herewith and required to be submitted by the applicant are or will be represented to be true and correct to the best of my knowledge and belief and are designed to be relied on by the local department of health in evaluating the same for purposes of issuing the permit applied for herein. I further under- stand that any falsification or misrepresentation may result in the denial of the application or revocation of any permit granted based upon said application and in legal action for per- jury as provided by law. Date c/ey Signed 4` PLEASE DRAW AND ACCURATE MAP TO YOUR PROPERTY L to-40 p @ 33 e thr Lr a9% 772 0°5 r Page 3 Application INDIVIDUAL SEWAGE DISPOSAL SYSTEM APPLICATION Approval by 944NER 'Voter H.Obuhanick County Official: ADDIESSP.O.Box 229 Aspen, Colo. 81611 PHONE925 2861 CONTRACTOR Abnhnnick linnet. Cn. ADDRESS P.A.Anx 229 Aspen, Colo. 81611 PHONE 925 -2861 PERMIT REQUEST FOR: x ) New Installation Alteration Repair Attach separate sheets or report showing entire area with respect to surrounding areas, topography of area, habitable building, location of potable water wells, soil percolation test holes, soil profiles in test holes. See page 4.) LOCATION OF PROPOSED FACILITY: County Garfield Near what City of Town Carbondale Lot Size 2.00 Ao. Legal Description Gov't lots 19 $ 10, eec 32,T75,R87W of the 6th P.M. Garfield Co.,Colo. WASTES TYPE:X Dwelling Transient Use Commercial or Institutional Non - domestic Wastes Other - Describe BUILDING OR SERVICE TYPE: Residential Number of bedrooms 3 Number of persons 3 X ) Garbage grinder X) Automatic washer X ) Dishwasher SOURCE AND TYPE OF WATER SUPPLY: x well spring stream or creek Give depth of all wells within 180 feet of system: 60' If supplied by community water, give name or supplier: GROUND CONDITIONS: Depth to bedrock: 20 plus feet. Death to first Ground Water Table: 3'-6" Percent ground slope:4% DISTANCE TO NEAREST COMMUNITY SEWER SYSTEM: N/A Was an effort made to connect to community system? no TYPE OF INDIVIDUAL SEWAGE DISPOSAL SYSTEM PROPOSED: X) Septic Tank Aeration Plant Vault Vault Privy Composting Toilet Recycling, potable use Pit Privy Incineration Toilet Recycling, other use Chemical Toilet Other - Describe: FINAL DISPOSAL BY: Absorption Trench, Bed or Pit Evapotranspiration Underground Dispersal Sand Filter Above Ground Dispersal Wastewater Pond Other - Describe: WILL EFFLUENT BE DISCHARGED DIRECTLY INTO WATERS OF THE STATE? no Page 2 ENGINEERS & CONSTRUCTORS s ES 1• Air ASSOC /ATES November 21, 1984 Mr. Ed Feld Garfield County Sanitarian 109 8th Street Glenwood Springs, Colorado 81601 RE: Obuhanick ET System Dear Ed: The purpose of this letter is to clear up two items relative to the above system design. First of all there was a miscalculation in the size of the ET Bed. The correct size is 2500 ft. calculated as follows: 1) Flow = 450 gpd x .75 = 337.5 gpd 1) 25% Reduction for low water use fixtures Area = 337.5 x 237 = 2500 ft. 32 The size of the ET Bed may thus be reduced to 50' x 50'. The second item pertains to peak flows. We did not use the 1.5 peaking factor that code requires for leachfields in our ET Bed design. Our rationale is that "peaking factors" do not apply to ET Bed design because a short term intermittent peak flow will not have an adverse effect on an ET Bed. The basis of ET Bed design is average daily flow. Floras exceeding average daily flow are offset by flows less the average daily flow. This is not the case with leachfields which must be designed to leach the peak flows since they do not have the storage capability to average out high and low flow over a long time period. If you have any questions please feel free to contact me. Sincerely, SCHMUESER && ASSOCIATES Rick Kinshella, P.E.u 'T "fJ RK/jj GA, NOV2 G1984 j aElr SCHMUESER & ASSOCIATES, INC. 1512 GRAND AVENUE, SUITE 210 • GLENWOOD SPRINGS, COLORADO 81601 • (303) 945.5468 Gareld County, CO Developed by Account Number   R111409 Parcel Number   239132200032 Acres 2 Land SqFt 0 Tax Area 011 Mill Levy 74.4140 Physical Address   310 FLYING FISH RD   CARBONDALE 81623 Owner Address   TAYLOR, DREW MICHAEL & NATALIA C 310 FLYING FISH ROAD CARBONDALE CO 81623 Total Actual Value   $109,340 Last 2 Sales Date  Price   6/4/2024  $950,000   6/4/2024  $950,000   Date created: 3/9/2025 Last Data Uploaded: 3/7/2025 10:43:21 PM 228 ft Overview Legend Parcels Roads Parcel/Account Numbers Owner Name Lakes & Rivers County Boundary Line