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Home My WebLink AboutOWTS Design 02.15.2022I29 CAINS LANE CARBoNDALE, CO 41623 970.309.5259 CARLA. OSTBERG@GMAIL. C OM RECE|VED Ê,fAy û + ZtZz ,r#il,i,iFifl.3?#il,i,Y lJl::I"l' I(: (,'ON 5( ! f-tl N (l February 15,2022 Project No. C1693 Mike Chmura mike@korultd.com Subsurface lnvestigation and Onsite Wastewater Treatment System Design 3-Bedroom Main Residence + 2-Bedroom Accessory Dwelling Unit (ADU) 12750 Hwy 82 Garfield County, Colorado Mike, CBO lnc. performed a subsurface investigation and completed an onsite wastewater treatment system (OWTS) design for the subject property. The 3.42-acre property is located outside of Carbondale, in an area where OWTSs and wells are necessary. Legal Description: Section: 27 Township: 7 Range: 88 A TR lN LOT 6 CONT. 3.12 AC ALSO A TR coNT. .34 AC 3.42 ACRES Parcel lD: 2393-27 1 -00-021 SITE CONDITIONS A 3-bedroom, single-family residence presently exists on the property. The residence is served by an existing OWTS. No records on the existing OWTS were available from Garfield County Land Explorer program. An inspection conducted by Altitude Septic included several recommendations including replacement of the existing septic tank serving the main residence. The existing STA is located within an easement on the adjoining property to the south. The soiltreatment area (STA) will remain in use. A new 2-bedroom accessory dwelling unit (ADU) is proposed in the area of an existing Barn to the southwest of the Main Residence. A new OWTS is proposed to serve this dwelling. An existing well on the property will serve both residences potable water. The well is located to the east of the proposed ADU. The well must be at least SO-feet from any proposed septic tank and at least 100-feet from the proposed STA. The proposed STA location has an approximate 27o/o slope to the southwest, with two flatter benches where the proposed beds will be placed. The proposed area is sparsely vegetated. 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. It appears the depiction of the property lines from Garfield County GIS is not correct. The actual southern property line extends approximately 7O-feet further south than shown on GIS per the survey. Page2 SUBSURFACE The subsurface was investigated on February 3,2022 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.l The materials encountered in Test Pit #1 consisted of reddish brown sandy loam to 1.S-feet where practical digging refusal was encountered. No groundwater was encountered. The materials encountered in Test Pit #2 consisted of reddish brown sandy loam to 2.O-feet where practical digging refusal was encountered. No groundwater was encountered. It is possible that additional depth for over-excavation can be achieved with larger equipment and/or rock- hammering. Native soils are classified as Soil Type 2, Sandy Loam. Rock content exceeds 65%. A pressure-dosed, over-excavated (with possible partial mounding) sand filter consisting of at least 3-feet of sand filter material (Secondary Sand) is proposed. A long term acceptance rate (LTAR) of 0.8 gallons per square foot will be used to design the OWTS, in accordance Garfield Gounty On-Site Wastewater Treatment System Reg ulations. Test Pit Backfill ' Carla Ostberg holds a Certificate of Attendance and Examination from the CPOWVisualand Tactile Evaluation of Soils Training. Page 3 Þ h Test Pit #1 View of Test Pit #1 View of proposed STA with two benches that will accommodate both beds Page 4 View of both Test Pits Test Pit #2 Test Pit #2 slightly deeper than Test Pit #1 Page 5 DESIGN SPECIFICATIONS 3-Bedroom Main Residence The Main Residence is served by an existing OWTS. Altitude Septic's September 28,2021 inspection report (enclosed) includes the following recommendations:. Replace septic tank.. Replace the line from the house to the tank so that the bulge is removed and the cast iron pipe is replaced with plastic.. Jet the outlet line all the way to the leach field to make sure it is clear. The new 4-inch diameter SDR-35 sewer line from the residence must include a double-sweep clean out and a minimum2o/o grade to the septic tank. The system installation must include a minimum 1000- gallon, two-compartment lnfiltrator@ poly septic tank with an effluent filter on the outlet tee. Other state- approved septic tanks may be substituted. Risers must bring the manhole lids to grade for access. lf more than one riser is added to the septic tank, an extension handle must be installed on the effluent filter. Both the inlet and outlet of the new septic tank must match èlevations of the existing sewer.lines. The existing STA will remain in use. 2-Bedroom ADU Desiqn Calculations: Average Design Flow = 75 GPD x 2 people/bedroom x 2 Bedrooms = 300 GPD LTAR = 0.8 GPD/SF 300 GPD / 0.8 GPD/SF = 375 SF The new OWTS design is based on 2-bedrooms. An average daily wastewater flow of 300 GPD will be used. For the purposes of this OWTS design, Benchmark Elevation has been established as the Finished Floor elevation of the ADU as 100'. CBO lnc. should be notified of any discrepancies or problems with grade elevations of proposed components during installation of the OWTS. *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 4-inch diameter SDR-35 sewer line exiting the ADU must have a double-sweep clean out and a minimum 2o/o grade to the septic tank. The system installation will include a 1OOO-gallon, two-compartment concrete Valley Precast septic tank with an Orenco@ Biotube Pump Vault and an Orenco@ PF3005 pump in the second compaftment of the septic tank. The floats should be set to dose approximately 65 gallons each pump cycle, allowing approximately B gallons of drain back after each pump cycle. A pump curue is enclosed. We recommend Valley Precast out of Buena Vista be contracted for start-up of the pumping system. OWTS Gomponent Minimum Elevation Primary Tank lnlet lnvert Approximate horizontal distance 20' I min.2o/o fall I min. 5" fall Automatic Distributing Valve Approximate horizontal distance 76' I min. 1o/o rise for drain back / min. 9.5" rise lnfiltrative Surface Approximate horizontal distance 16'l min. 1o/o fall I min.2" fall Page 6 Table 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 1o/o 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 to through 1.5-inch diameter distribution lines to two beds, eaehT' x31.25'. The over-excavation is expected to extend 2.S-feet below native grade, so partial mounding will be necessary, and height above native grade will depend on the depth of the over-excavation. A minimum of 3- feet of sand filter material will be installed in the over-excavated footprint. 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 .S-inches in diameter with 5/32-inch diameter orifices facing down, spaced 2-feet on center, installed on the center of each GeoMatrM with the filter fabric over the laterals. Two 39" wide GeoMatrM sheets must be placed on the 7-foot wide bed. All material associated with the GeoMatrM installation must be proprietary products associated with the GeoMatrM, including orifice shields and geotextile fabric. Manufacturer instructions must be followed regarding installation of the GeoMatrM. Each 1.S-inch diameter lateral must end in a sweeping ell facing up with a ball valve for flushing. Valves should be placed in a 1O-inch sprinkler box for access. Laterals must be covered by a soil separation fabric and at least 'l-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 GeoMatrM. lnspection 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 mounded portions of the beds must have a minimum 3:1 slope (horizontal:vertical). Fill over the beds may tie into grade on the uphill side and must extend to match grade on the downhill side with a minimum 3:1 slope. 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. Max = 83 gal. (300 GPD x25o/o + 8 oal drain back) Min. 40 gal. (B gal x 4) + B gal drain back Dose Range Dose Setting 65 gallons/dose B gallons drain back (76' I 1.5" diameter oump line) Float Separation 1000 gallon 2-compartmet Valley Precast concrete septic tank 9.5" on/off float separation 20.3 gallons per minute (GPM)32.7 feettotal dynamic head fiDH) Pump Criteria PageT COMPONENT SPECIFICATIONS The component manufacturers are typical of applications used by contractors and engineers in this area. GBO lnc. 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. 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 lnc. 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 th roughout the installation. INSTALLAT¡ON OBSERVATIONS CBO lnc. 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 lnc. should be notified 48 hours in advance to observe the installation. ln 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 COMPONENT MANUFACTURER MODEL NO.COMMENTS Septic Tank lnfiltrator@ M 1060-2CP 1OOO-gallon,2- :ompartment poly septic :ank Effluent Filter Orenco@ 4-inch diameter effluent filter (Full Size) Septic Tank Valley Precast tem # 1000T-2CP-HH 100O-gallon,2- compartment concrete septic tank with HH pump in second compartment Pump Orenco@ PF300511%HP 120 Volt Biotube ProPak Pump Packaqe Orenco@ BPP30DL)Vault, F¡lter, Control Panel ldemand dose) Tank Risers and Lids Orenco@ Double-walled PVC Risers and Lids (24" diameter) ADV Orenco@ v6402A{1.5" lnlet and Outlets ADV R¡ser and L¡d Orenco@ Double-walled PVC Risers and Lids (30" diameter) orir¡ce sh¡elds GeoMatrix Systems, LLC 56 orifice shields Flushing Assembly Orenco@ 1.5" drameter '12) Á 45" or 90" long sweep only total) GeoMatrM GeoMatrix Systems, LLC 12b, GeoMapu (39,, sheets) Page 8 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 additionalwater 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. lf an effluent filter or screen has been installed in the OWTS, we recommend this filter or screen be cleaned annually, or as needed. lf 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 lf 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 9 LIMITS: The design is based on information submitted. lf soil conditions encountered are different from conditions described in report, CBO lnc. 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 lnc.Reviewed By (ø"nb tstú","/,E Carla Ostberg, MPH, REHS Romeo A. Baylosis, PE 3-4-2022 t I h rr}a38823 Pump Selection for a Pressurized System - Single Family Residence Project 12750 Hwy 82 Parameters 300Discharge Assembly Size Transport Length Before Valve Transport Pipe Class Transport Line Size Distr¡buting Valve Model Transport Length After Valve Transpo¡t Pipe Class Transport Pipe Size Max Elevation Lift Man¡fold Length Manifold Pipe Clâss Manifold Pipe Size Number of Laterals per Cell Lateral Length Laterãl Pipe Class Lateral Pipe Size Orifice Size Orifice Spacing Residual Head Flow Meter 'Add-on' Fr¡ct¡on Losses Calculations 1.25 7A 40 1.50 6402 16 40 1.50 l8 J 40 1.50 4 29.5 40 1.50 5132 2 5 None 0 feet inches inches feet ¡nches feet feet inches feet inches inches feet feet inches feet oo1! Eo ït Gg¡ .9 E a! o tú Ê 250 200 150 100 50 PumpData 15 20 25 Net Discharge (gpm) 30 35 40 M¡n¡mum Flow Rate per Or¡fice Number of Orifices per Zone Total Flow Rate per Zone Number of Laterals per Zone % Flow Differential lsvlast Or¡fice Transport Velocity Before Valve Transport Velocity After Valve Frictional Head Losses 0.68 20.3 2 0.7 gpm gpm o/o fps fps Loss through Discharge Loss in Transport Before Valve Loss through Vâlve Loss in Transport after Valve Loss in Manifold Loss in Laterals Loss through Flowmeter 'Add-on' Frict¡on Losses Pipe Volumes 2.9 1.9 4.3 0.4 0.0 0.1 0.0 0.0 feet feet feet feet feet feet feet feet 0 0 5 10 Vol of Transport Line Before Valve 8.0 Vol of Transport Line After Valve 1.7 Vol of Manifold 0.3 Vol of Laterals per Zone 6.2 Total Vol Before Valve 8.0 Total Vol After Valve 8.2 !quirements gals gals gals gals gals gals PF3005 High Head Effluent Pump 30 GPM, ,1/2HP 1151230V 1Ø 60H2,200V 3Ø 60Hz PF3007 High Head Eff¡uent Pump 30 GPM,3/4HP 230V 1Ø 60H2,20O1460Y 3Ø 60Hz PF3010 High Head Effluent Pump 30 GPM, lHP 230V 1Ø 60H2,2001460V 3Ø 60Hz PF3015 High Head Effluent Pump 30 GPM, r-1l2HP 230V 1Ø 60Hz'20012301460V 3Ø 60Hz gpm SY*TËMS @ I \\ System Curve: - Pump Curve:* PUmp (Jptrmal Kange: Operating Po¡nt:O o Des¡gn Point: 20.3 32.7 feet