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Home My WebLink AboutOWTS Design Report 01.27.2021January 27, 2021 Michael puller Architects C/O Ms. Kelleigh Condon 23400 Two Rivers Road, Suite 41 Basalt, CO 81621 MOUNTAIN CROSS ENGINEERING, INC. Civil and Environmental Consulting and Design RE: Anderson Residence, 278 Ronce Lane, Garfield County, CO — OWTS Report Dear Kelleigh: The purpose of this correspondence is to inform you about the onsite wastewater treatment system (OWTS) designed for the reconstruction project of the Anderson Residence. The project proposes to raze and construct a new residence. The project is located in Garfield County, just to the west of the Eagle County line near Carbondale, CO at 278 Ronce Lane. The main floor of the residence will be a gravity system to a conventional septic tank where a pump will pressure dose to a leach field comprised of a bed of infiltration chambers. The plumbing of the lower level will need a sewer ejector pump to lift into the gravity system. The residence will be :served by an existing well. The OWTS is not within a 100 -year :flood plain boundary. There are practical constraints that you should be aware of when considering the proper design, construction, and operation. Subsurface The soil was determined to be R2A soils with an LTAR value approximated as 0.50 gallons per day per square foot (GPD/sq.ft.) from soil. evaluations performed by CTL Thompson. A profile hole was excavated and an inspection revealed that no bedrock or high groundwater table is within an 8' depth of the leaching area. Design Calculations The residence is proposed to be 4 bedrooms with a 1 bedroom caretaker unit above the garage. Using Garfield County Table 6-1 for a 5 -bedroom residence; this yields 600 gallons per day (GPD) total. The design calculations for sizing of the septic system and the leach field follow: • Anderson Residence: 5 bedrooms = 600 GPD • Based on soil evaluation and percolation tests results, LTAR = 0.50 GPD/sq.ft. • Minimum absorption area = 600 GPD / 0.50 = 1,200 sq. ft. • Reductions in soil treatment areas for bed treatment with pressure dosing =1,200 sq. ft. * 0.7 * 1.0 = 840 sq.ft leach area • Required chambers = (840 sq.ft)/(12.34 sq.ft/chamber) = 68 chambers, Use four rows of 17 chambers, 68 chambers • Required septic tank volume = 1,500 gallons per Garfield County Table 9-1 • Dosing frequency = 4 doses per day; dose volume = 600 GPD / 4 doses = 150 gal./dose Pump(s) should provide 70 gpm at 25' of Total Dynamic Head 826142 Grand Avenue, Glenwood Springs, CO 51601 9: 970,945.5544 F: 970.945.5558 www.mountaincross-eng.com Ansderson Residence January, 2021 Page 2 of 3 • PVC lateral distribution pipes should be Schedule 40, 1-1/2" in diameter. • PVC supply and manifold pipes should be Schedule 40, 2" in diameter. • Each lateral pipe should have seventeen 4" diameter holes drilled in the lateral at 5' spacing with the first hole located at 2.5' from the start of the bed. The components manufacturers are typical for the area. Alternatives may be considered by contacting this office. Construction must be in accordance with the specifications of Garfield County Environmental Health, the OWTS permit, and this design, Topsoil should be placed over the OWTS and planted with native grasses. No large vegetation and/or plants with taproots should be planted over the :absorption. area nor grasses that require excessive irrigation. Setbacks The location for the septic and dosing tanks are limited by setback requirements per Garfield County and the State of Colorado, These include: • 50' FROM WELL ■ 10' FROM WATER SUPPLY LINE • 5' FROM BUILDING WITH BASEMENT • 10' FROM PROPERTY LINE • 10' FROM. LINED POND, DITCH, OR .STREAM • 50' FROM WATER BODY • 10' FROM CREST OF BANK • 5' FROM LEACH FIELD The leach field setback requirements are: • 100' FROM WELL • 25' FROM WATER SUPPLY LINE • 20' FROM BUILDING WITH BASEMENT • 10' FROM PROPERTY LINE • 10' FROM LINED POND, DITCH; OR STREAM • 50' FROM WATER BODY • 25' FROM CREST OF BANK • 5' FROM SEPTIC TANK The setback requirements deal primarily with buildings and potential contamination from the septic tank, dosing tank, and leach field to either culinary water or surface water. These setbacks have been included on the plans for reference. There is an existing pond that is lined and must remain lined to conform to the required setbacks. The leach field will need to be located out of the required setback distance from the top of bank. Mountain Cross Engineering, Inc. Civil and Environmental Consulting and Design 826 'h. Grand Avenue, Glenwood Springs, CO 81601 P: 970,945.5541 F: 970.945.5558 www.mountaincross-enq.com Ansderson Residence January, 2021 Page 3 of 3 Operation Information and Maintenance The Owner will need to be responsible for the operation and management of the OWTS. Geo - fabrics or plastics should not be used over the absorption area. No heavy equipment, parking of machinery, or materials should be placed on the absorption area. Livestock should not graze on the absorption area. Plumbing fixtures should be checked to ensure that no additional water is being discharged to OWTS; for example, running toilets or leaky faucets can discharge hundreds of gallons of water a day and harm the absorption area. Garbage disposal use should be minimized, and non -biodegradable materials should not be placed into the OWTS. Grease should not be placed in drains and grease traps should be installed upstream of the septic tank but downstream from any kitchen. Loading from a water softener should not be discharged into the OWTS. No hazardous wastes should be directed into the OWTS. The OWTS is engineered for domestic waste only. The Owner will likely need to contract with a septic system cleaner to clean the septic tank every two years, or as needed gauged by measurement of solids in the tank: The standards of performance for the septic system cleaner are recommended to he the following, at a minimum: 1. The Systems Cleaner shall be licensed. 2. The Systems Cleaner, when cleaning a septic tank, shall remove the liquid, sludge, and scum, leaving no more than three (3) inches depth of sewage in a septic tank. 3. The Systems Cleaner shall maintain his equipment so as to ensure that no spillage of sewage will occur during transportation, and that its employees are not subject to undue health hazards. 4. The Systems Cleaner shall dispose of the collected sewage only at a designated site recognized by the Board of Health. Construction Observation Prior to being backfilled, the construction of the OWTS and all of the components will need to be observed by representatives of Mountain Cross Engineering, Inc. The conclusions and opinions that are expressed above are based on the information available at the time of preparation of this report. Any additional information presented afterward may require that these opinions and the design be modified. Thank you for the opportunity to provide this report. Feel free to call if you have any questions, concerns, or comments. _ Sincerely, u Jai.' Cross En in ering, Inc. is Hale, PE - r . .r • f _ 4 , y',r.'C�'fr7 r) `r J.V27t f f Mountjin Cross Engineering, Inc. ci rE ,` t E iron r4i7,:o ili:' Consulting and Design 826 ',< Grav :r u. • Springs, CO 81601 P; 970.945.554,1 E; : 0.1,4 .d v:w.rnountaincrlass -eng.corn