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Home My WebLink AboutOWTS Designstìt¡'l.r(' <'( )¡¡saf 't.'t' f :\i(; June 27,2021 i 29 CAINS LANE CARBONDALE,CO 4I623 970.309.5259 CARLA. oSTBERG@GMAIL. COM RHÜËIVED , FFB ilg 2A2? "'îtri,i,ilf,fi?#il,HProject No. C1614 MichaelRitter mcritter@live.com Subsurface lnvestigation and Onsite Wastewater Treatment System Design 2-Bedroom Residence 2053 Grass Mesa Road Garfield County, Golorado Michael, CBO lnc. performed a subsurface investigation and completed an onsite wastewater treatment system (OWTS) design for the subject residence. The 39.9-acre property is located outside of Rifle, in an area where OWTSs are necessary. Legal Description: Section:26 Township:6 Range:93 SWSW Subdivision: GRASS MESA RANGH Lot: 2239.9 ACRES Parcel lD: 2177 -263-00-324 SITE CONDITIONS The property is currently undeveloped. A 2-bedroom residence is proposed near the southwest corner of the property. The residence will be served potable water from a cistern that, initially, will not be directly connected to a well. The water line will come from the south and will not come within 5-feet of any sewer line, 1O-feet of the septic tank, and 2S-feet of the soil treatment area (STA). Any future well must be at least SO-feet from the septic tank and 100-feet from the STA. The proposed STA location is relatively flat, with less than a 5% slope to the north. The proposed area is vegetated with native grasses and sage. Mature pinyon trees are present to the east of the proposed area. There should be no traffic or staging of material over the future STA site to avoid compaction of soils priorto construction of the STA. SUBSURFACE The subsurface was investigated on June 10,202'l by dígging two soil profile test pit excavations ffest Pits) A visual and tactile soil analysis was completed by Carla Ostberg at the time of excavation.l ' Carla Ostberg holds a Certificate of Attendance and Examination from the CPOW Visual and Tactile Evaluation of Soils Training. Page 2 The materials encountered in Test Pit #1 consisted of dark brown topsoil to 1.S-feet, underlain by tan calcareous clay matrix to a maximum depth explored of 7.O-feet where digging became difficult. No bedrock or groundwater was encountered. The materials encountered in Test Pit #2 were similar to those in Test P¡t #1. Test Pit #2 was explored to a maximum depth of 7.O-feet. No bedrock or groundwater was encountered. A sample of the soils 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 firm. Soil texture was both gritty and smooth. Soils were consistent with Soil Type 2 with moderate structure grade. A long term acceptance rate (LTAR) of 0.6 gallons per square foot will be used to design the OWTS. Test Pit #1 Sieved sample Page 3 Test Pit Test Pit #2 View of Test Pit 1 looking toward Ê!W{?¡.s.gl¡qe:ær*ìryi::i:''r 1: -'- :' Ì, Backfill \, * Page 4 Test Pit #2 DESIGN SPECIFICATIONS Desiqn Calculations: Average Design Flow = 75 GPD x 2 people/bedroom x 2 Bedrooms = 300 GPD LTAR = 0.6 GPD/SF 300 GPD / 0.6 GPD/SF x 1.0 (gravity trenches) x 0.7 (chambers) = 359 t- 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 100' (finished floor). The sewer line should exit the residence at approximate 98'. 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 OWTS Minimum Elevation Primary Tank lnlet lnvert Approx. horizontal distance '13' / min. 2% fall to seotic tank / min. 3.25" tall Distribution Box Approx. horizontal distance 12' I min. 1Yo fall I min. '1.625" fall to distribution box lnfiltrative Surface Approx. horizontal distance 15' to farthest trench / min. 1o/o fall / min. '1.875" fall to farthest trench installation due to site conditions Page 5 The 4-inch diameter SDR-35 sewer line exiting the residence must have a double-sweep clean out and a minimum 2o/o grade to the septic tank. The system installation must include a 1O00-gallon, two-compartment poly lnfiltrator@ septic tank with an efflueñt filter on the outlet tee. A concrete septic tank may be substituted, if desired. 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. Effluent will gravity flow to a distribution box, and then to three gravelless chamber 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 trench. Each trench will consist of 10 'Quick 4' Standard Plus lnfiltrator@ chambers for a total of 30 chambers and 360 square feet of infiltrative area. There must be at least 4-feet of undisturbed soil between each trench. lnspection ports must be installed at the beginning and end of each trench. Ports may be cut to grade and placed in sprinkler boxes for access. 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 throughout 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. COMPONENT IMANUFACTURER MODEL NO.COMMENTS Septic Tank llnfiltrator@ tM-1060-2CP 1 000-9allon, 2-compartment oolv seotic tank 3iotube Effluent Filter lorenco@ Full Size Effluent Filter and housinq Iank Risers and Lids lorencoo Double-walled PVC Risers and Lids (24" diameter) Distribution Box lPolvLok Distribution box, flow equalizers, risers, lid Shambers ilnfiltrator@ Standard Plus 30 'Quick 4' Standard Plus Chambers Page 6 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 |ine 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 paôt<et. Photographs of the installation and final cover are also requested to supplement our installation documentation. REVEGETATION REQUIREMENTS An adequate layer of good qualiÇ topsoil capable of supporting revegetiation 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 inigation 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 propertyr. The property owner is responsible for maintaining service contracts for manufactured units, altemating 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. 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 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. PageT 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. (,r"r,üy }S+buE Carla Ostberg, MPH, REHS