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HomeMy WebLinkAboutEngineer's OWTS Design 5020 County Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email: kaglenwood@kumarusa.com www.kumarusa.com Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado ONSITE WASTEWATER TREATMENT SYSTEM DESIGN EXISTING WILLOW HOUSE OUT OF BOUNDS RANCH 860 COUNTY ROAD 112 (COULTER CREEK ROAD) GARFIELD COUNTY, COLORADO PROJECT NO. 24-7-380.02 AUGUST 14, 2024 PREPARED FOR: MIKE HUITT 2491 EAST MESA ROAD MOAB, UTAH 84532 mikehuitt71@gmail.com Kumar & Associates, Inc. Project No. 24-7-380.02 TABLE OF CONTENTS INTRODUCTION ...................................................................................................................... - 1 - PROPOSED CONSTRUCTION ................................................................................................ - 1 - SITE CONDITIONS ................................................................................................................... - 1 - SUBSURFACE CONDITIONS ................................................................................................. - 1 - OWTS ANALYSIS .................................................................................................................... - 2 - DESIGN RECOMMENDATIONS ............................................................................................ - 3 - SOIL TREATMENT AREA................................................................................................... - 3 - OWTS COMPONENTS ......................................................................................................... - 4 - OWTS OPERATION AND MAINTENANCE.......................................................................... - 6 - OWTS HOUSEHOLD OPERATION .................................................................................... - 6 - OWTS MAINTENANCE ....................................................................................................... - 7 - OWTS CONSTRUCTION OBSERVATION ............................................................................ - 7 - LIMITATIONS ........................................................................................................................... - 7 - FIGURES FIGURE 1 – OWTS SITE PLAN FIGURE 2 – USDA GRADATION TEST RESULTS FIGURE 3 – SOIL TREATMENT AREA CALCULATIONS FIGURE 4 – SOIL TREATMENT AREA PLAN VIEW FIGURE 5 – SOIL TREATMENT AREA CROSS SECTION ATTACHMENTS NORWESCO/SNYDER 1,500 GALLON, TWO-CHAMBER SEPTIC TANK DETAIL TUF-TITE 4-HOLE DISTRIBUTION BOX Kumar & Associates, Inc. Project No. 24-7-380.02 INTRODUCTION This report provides the results of a design for a new onsite wastewater treatment system (OWTS) for the existing Willow House located at the Out of Bounds Ranch, 860 County Road 112, Garfield County, Colorado. The project site is shown on Figure 1. The purpose of the report is to provide design details for the OWTS in accordance with Garfield County Environmental Health Department Onsite Wastewater Treatment System Regulations and the Colorado Department of Public Health and Environmental Regulation #43. The services are supplemental to our agreement for professional services to Mike Huitt dated June 26, 2024. PROPOSED CONSTRUCTION The Willow House is located in the near the southeast corner of the property as shown on Figure 1. The residence has three bedrooms. The OWTS will be designed for three bedrooms, see Figure 3. The current OWTS has failed and is backing up into the residence. The location and design of the existing STA are unknown. The proposed soil treatment area (STA) for the OWTS will be located southwest of the residence as shown on Figure 1. Water service is provided by an onsite well north of the residence. The route of the water supply line from the well to the structures is not known at the time of this report. If proposed construction is different than that described, we should be contacted to re-evaluate our design recommendations. SITE CONDITIONS The ranch site, shown on Figure 1, is developed with various residences, outbuildings and fields. The ranch mostly consists located north and east of County Road 115, and east of County Road 112. The ranch consists mostly of pastures. Coulter Creek trends toward the south about 500 feet west of the proposed STA. The terrain is gently to moderately sloping down to the west. Vegetation consists of pasture grass with various deciduous trees. SUBSURFACE CONDITIONS The field exploration for the OWTS was conducted on July 29, 2024. Two profile pits (Profile Pits 1 and 2) were excavated with a mini-excavator at the approximate locations shown on Figure 1 to evaluate the subsurface conditions at the new soil treatment area for the OWTS. The pits were logged by a representative of Kumar & Associates. Logs of the profile pits are provided below. - 2 - Kumar & Associates, Inc. Project No. 24-7-380.02 Log of Profile Pit 1 Depth USDA Classification 0-2’ TOPSOIL; organic Loam, strong blocky structure, firm, moist, dark brown. 2’-7’ CLAY LOAM; gravelly, strong blocky structure, very stiff, slightly moist, brown. • Disturbed bulk sample from 4 to 5 feet depth. • Bottom of pit @ 7 feet depth. • No groundwater or redoximorphic features observed at the time of pit excavation. Log of Profile Pit 2 Depth USDA Classification 0-1’ TOPSOIL; organic Loam, strong blocky structure, firm, moist, dark brown. 1’-7’ CLAY LOAM; strong blocky structure, very stiff, moist, brown. • Bottom of pit @ 7 feet depth. • No ground water or redoximorphic feature observed at the time of pit excavation. The soils encountered in profile pits, below about 1 to 2 feet of organic topsoil, consisted of Clay Loam that extended down to the pit depths of 7 feet. Hydrometer and gradation analyses were performed on a disturbed bulk sample of the soils from Profile Pit 1 from 4 to 5 feet depth with the results provided on Figure 2. The tested sample (minus No.10 size sieve fraction) classifies as Clay Loam per the USDA system. No free water was encountered in the pits nor indications of seasonal high groundwater were observed at the time of the pit excavations. Based on the subsurface conditions and laboratory testing, the design soils have been classified as Type 2 per State regulations, which equates to a long-term acceptance rate (LTAR) of 0.35 gallons per square foot per day. OWTS ANALYSIS Based on the site conditions and profile pit evaluations, the evaluated area should be suitable for a conventional infiltration disposal system. The STA will consist of chambers in a trench configuration based in the Clay Loam soils. The STA will be sized for 3 bedrooms and 6 persons with an average daily flow of 75 gallons per person, and an LTAR of 0.35 gallons per square foot per day in the natural soils. The effluent will gravity flow from the Willow House to a septic tank for primary treatment and then gravity flow to the STA for dispersal and final treatment. Any basement area facilities wastewater may need to be pumped to the septic tank and should designed by others. The STA will consist of three trenches with Infiltrator Arc 36 chambers. Equal distribution will be provided to the chambers and trenches by a distribution box. The existing septic tank is inadequate for the proposed OWTS. It should be removed or abandoned per County regulations. The location of the existing STA is unknown. We should - 3 - Kumar & Associates, Inc. Project No. 24-7-380.02 be notified for further recommendations if the STA is encountered during construction of the new STA. The route of the water supply line is not known but appears to be outside of any setback. The required setback of the water line from the septic tank is 10 feet, 5 feet for sewer and effluent lines, and 25 feet from the STA. We should be notified for additional recommendations if any of the setbacks cannot be met. DESIGN RECOMMENDATIONS The design recommendations presented below are based on the proposed construction, the site and subsurface conditions encountered, and our experience in the area. A layout of the proposed OWTS components is provided on Figure 1. If conditions encountered during construction are different than those that are described in this report, we should be contacted to re-evaluate our design recommendations. SOIL TREATMENT AREA • The STA will consist of three trenches with 20 Infiltrator Arc 36 chambers placed in each trench (60 chambers total) in the natural soils. Equal distribution will be provided to the trenches by a distribution box. • The STA was sized based on an LTAR of 0.35 gallons per square feet per day. • Each chamber was allowed 12 square feet of area. A 30% reduction for use of Infiltrator chambers in a trench configuration were applied to the size of the STA. The total STA design size is 900 square feet. Soil treatment area calculations are shown on Figure 3. • Trenches should be a maximum of 48 inches deep. • A minimum of four feet of undisturbed soil between the trenches is required. • The trenches should be oriented along ground contours to minimize soil cut and cover. • The base and sidewalls of the trench excavations should be scarified prior to the chamber placement. • A minimum of 12 inches and a maximum of 24 inches of cover soil should be placed over the chambers. • Backfill should be graded to deflect surface water away from the STA and should be sloped at 3 horizontal to 1 vertical or flatter. A swale to divert surface water flow away from the STA may be needed upslope of the STA. • Disturbed soil should be re-vegetated as soon as possible with a native grass mix. No trees, shrubs or other plants with deep roots should be planted on or near the STA as this may damage the system piping. • Four-inch diameter inspection ports should be installed vertically into the knockouts provided in the first and last chambers in each trench. The inspection port piping should be screwed into the top to the chambers and should not extend down to the ground - 4 - Kumar & Associates, Inc. Project No. 24-7-380.02 surface inside the chambers. The inspection ports should extend at least 8 inches above the finished ground surface or be protected in a valve box at finished grade. • The STA must be a minimum of 25 feet from any potable water supply lines. • A plan view of the STA is presented on Figure 4 and a cross section of the STA is presented on Figure 5. OWTS COMPONENTS Recommended OWTS components provided below are based on our design details and our experience with the specific component manufacturers. Equivalent components may be feasible but need to be approved by us prior to construction. Septic Tank • The septic tank must be at minimum a 1,000 gallon, two-chamber tank. • A Norwesco/Snyder 1,500-gallon, two-chamber septic tank should be used for primary treatment is available and is suitable. A detail of the tank is provided as an attachment to the report. • The tank must be a minimum of 10 feet from any potable water supply lines. • The tank must be set level. The excavation bottoms must be free of large rocks or other objects that could damage the tanks during placement. A road base or gravel bedding material may be needed to prevent tank damage during placement and act as a leveling course. • The tank lids must extend to final surface grade and made to be easily located. • Install the tanks with 2 feet minimum cover soil for frost protection. Maximum tank soil cover is 4 feet. Sewer Pipe • The sewer line to the septic tank should not be less than the diameter of the building or other drains and not less than 4 inches in diameter. • The existing sewer line should be removed and replaced. • The sewer pipes should have a rating of SDR35 or stronger. Schedule 40 PVC pipe is required beneath any driveway or gravel surfaces. • The sewer pipes should be sloped between 2% to 4% to help limit disturbance of solids in the tank and potential sewage bypass of the first chamber of the tank. If a steeper slope is needed, this can be accomplished with vertical step-downs in the sewer line. • A minimum 36 inches of cover soil should be provided over the sewer pipes. Paved or graveled areas, patios or other areas without vegetative cover may be more susceptible to frost and we recommend 48 inches of soil cover over the sewer pipes in these areas, and the pipes be insulated on top and sides with 2-inch-thick blue foam insulation board. If - 5 - Kumar & Associates, Inc. Project No. 24-7-380.02 adequate soil cover is not possible, we should be contacted for re-evaluation prior to installation. • The sewer pipe should be bedded in compacted ¾-inch road base or native soils provided that the native soils contain no angular rocks or rocks larger than 2½ inches in diameter to help prevent settlement of the pipe. Sags in the pipe could cause standing effluent to freeze and damage the piping. • Install cleanout pipes within 5 feet of the building foundation, where the sewer pipe bends 90 degrees or more and every 100 feet of sewer pipes. • All 90-degree bends should be installed using a 90-degree long-sweep or by using two 45-degree elbows. • The sewer line location shown on Figure 1 is considered conceptual. We assume that there will be only one sewer line exiting the structure. It is the responsibility of the owner/contractors to locate all sewer line exit locations and connections to the septic tank. We should be notified if there are other sewer lines exiting the building. Effluent Transport Piping • The effluent transport pipe should be 4-inch diameter SDR35 piping sloped at a 2% minimum to flow from the septic tank to the distribution box and from the distribution box to each trench. Piping should extend at least 6 inches into the top knockout provided in the Infiltrator end caps and be screwed in place. Splash plates should be installed beneath the inlet piping to help limit scouring of the infiltrative soil surface in the chambers. • The effluent transport pipe should be bedded in compacted ¾-inch road base or native soils provided that the native soils contain no angular rocks or rocks larger than 2½ inches in diameter to help prevent settlement of the pipe. Sags could cause standing effluent to freeze and damage to the piping. • A minimum 18 inches of cover soil should be provided over the effluent transport pipe. Paved areas, patios or other areas without vegetative cover may be more susceptible to frost. We recommend 48 inches of soil cover over the effluent pipe and insulation with at least 2 inches of rigid foam insulation in these areas. If adequate cover soil is not possible, we should re-evaluate the condition prior to installation. • Schedule 40 PVC pipe is required underneath driveway surfaces and should be provided with at least 48 inches of soil cover and be insulated on top and sides with 2-inch-thick rigid foam insulation board. • All 90-degree bends should be installed using a 90 degree long-sweep or by using two 45-degree elbows. - 6 - Kumar & Associates, Inc. Project No. 24-7-380.02 Distribution Box • The distribution box will be used to equally divide effluent flow between the trenches. We recommend the Tuf-Tite 4-Hole Distribution Box since it is easily accessible from ground surface for maintenance. A copy of the distribution box detail is provided as an attachment to this report. • The distribution box outlet pipes should be equipped with Tuf-Tite speed levelers for ease of initial setup and adjustment over time. • The distribution box should be a minimum of 18 inches below grade with risers and an access lid at or above grade. • The distribution box must be accessible from ground surface for inspection and maintenance per the State guidelines. • The effluent line from the septic tank should be directed downward into the distribution box with a 90-degree elbow inside the box. • The distribution box must be installed level on a compacted road base subgrade to ensure equal effluent distribution. If settlement of the distribution box occurs, unequal effluent distribution may take place which could cause hydraulic overload of one of the trenches and potential failure. The distribution box should be monitored periodically, and the speed levelers should be adjusted as necessary for levelling. • The ground surface above and around the distribution box should be graded to drain away surface water to prevent standing water near the distribution box which could freeze or cause settlement. OWTS OPERATION AND MAINTENANCE The OWTS will require periodic inspection and maintenance to function properly. A properly designed, installed and maintained system can greatly increase its lifespan. The level of maintenance will vary depending on the complexity of the system and water use habits of the residents. We recommend that an OWTS Operation and Maintenance (O&M) Manual be developed. Below are some basic recommendations for the OWTS O&M. OWTS HOUSEHOLD OPERATION • Use of high efficiency water fixtures is recommended to decrease the hydraulic load on the OWTS system. • Fix plumbing leaks immediately as this may cause a hydraulic overload of the soil absorption system. • Do not irrigate the area on top of or directly upgradient of the soil absorption field as this may cause a hydraulic overload. • Do not dispose of household waste down drains as this may clog or damage OWTS components. Examples of household waste includes: dental floss, cotton swabs, coffee grounds, paper towels, feminine products and many other kitchen and bath items. - 7 - Kumar & Associates, Inc. Project No. 24-7-380.02 • Use of kitchen garbage disposals is not recommended. If a garbage disposal is utilized, kitchen wastewater should be screened thoroughly. Many kitchen solids are not decomposed in the septic tank and may cause increased tank pumping frequency. • Do not dispose of household chemicals, greases, oils, paints, hot tub water or water softener backwash in household drains. A separate drywell, if feasible, may be necessary for hot tub water or water softener backwash disposal. • Limit the use of bleach as this may harm useful bacteria in the septic tank and soil absorption system. • Liquid dishwasher and clothes washer detergent is recommended for households served by an OWTS. Clay substances used as fillers in powder detergents may result in clogging of the soils absorption system. OWTS MAINTENANCE • Inspect the septic tank, distribution box and STA at least annually for problems or signs of failure. • The filter should be cleaned at least annually by spray washing solids into the first chamber of the septic tanks. • The septic tanks should be pumped and cleaned every 3 to 5 years depending on use. Longer pumping intervals may increase the amount of solids that reach the STA, which may shorten its life span. • Pumping of the septic tanks should take place when the level of the sludge and scum layers combined take up 25 to 33% of the capacity of the first chamber of the tank. OWTS CONSTRUCTION OBSERVATION The Garfield County Environmental Health Department requires that the designer of the system provide a record drawing and certification of the OWTS construction (As-Built inspection). We should be provided with at least 48-hour notice prior to the installer needing the inspections. Prior to issuance of our certification letter, we require observation of all system components prior to backfill. The number of site visits required for the inspection will depend on the installer’s construction schedule. LIMITATIONS We have conducted this design in accordance with generally accepted engineering principles and practices in this area at this time. We make no warranty either expressed or implied. The recommendations provided in this report are based on the site conditions, profile pit evaluations and soil texture analysis, the proposed construction and our experience in the area. Variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered during construction appear different from those described in this report, we should be notified so that re-evaluation of the recommendations may be made. Kumar & Associates SILT COBBLES COARSE GRAVEL MEDIUMMEDIUMV. FINE SAND CLAY FINE CO.FINEV. CO.CO.FINE Kumar & Associates Kumar & Associates Kumar & Associates Notes: &KDPEeUssKoXOGEeLQstDOOeGOeYeOoQDsFDULILeGJUoXQGsXUIDFe&oQFUetesDQGPD\EeXseGDsDOeYeOLQJFoXUseLI QeFessDU\ &DUesKoXOGEetDNeQE\tKeFoQtUDFtoUtoDYoLGFoPSDFtLoQoItKeQDtLYesoLOsLQtKetUeQFKDUeDs7KeEDseDQGsLGeZDOOsoI tUeQFKe[FDYDtLoQssKoXOGEesFDULILeGSULoUtoFKDPEeULQstDOODtLoQ $OOSLSLQJsKoXOGKDYeDUDtLQJoI6'5oUstUoQJeU &KDQJestotKLsGesLJQsKoXOGQotEePDGeZLtKoXtFoQsXOtDtLoQDQGDSSUoYDOE\.XPDU $ssoFLDtes 5eIeUtotKe*DUILeOG&oXQt\2QsLte:DsteZDteU6\steP5eJXODtLoQsIoUotKeUDSSOLFDEOesSeFLILFDtLoQs Kumar & Associates Notes: &KDPEeUssKoXOGEeLQstDOOeGOeYeOoQDsFDULILeGJUoXQGsXUIDFe&oQFUete sDQGPD\EeXseGDsDOeYeOLQJFoXUseLIQeFessDU\ &DUesKoXOGEetDNeQE\tKeFoQtUDFtoUtoDYoLGFoPSDFtLoQoItKeQDtLYesoLOsLQ tKetUeQFKDUeDs7KeEDseDQGsLGeZDOOsoItUeQFKe[FDYDtLoQssKoXOGEe sFDULILeGSULoUtoFKDPEeULQstDOODtLoQ &KDQJestotKLsGesLJQsKoXOGQotEePDGeZLtKoXtFoQsXOtDtLoQDQGDSSUoYDO E\.XPDU $ssoFLDtes SHEET 1 OF 1 DRAWN CHECKED QA MFG APPROVED Todd Bolzer 5/8/2012 DWG NO TITLE 1500 GALLON LOW PROFILE SEPTIC TANK - IAPMO SIZE B SCALE: 1/16 NORWESCO, INC., ST. BONIFACIUS, MN REV REVISION HISTORY ZONE REV DESCRIPTION DATE APPROVED 40 6 MATERIAL: HIGH-DENSITY POLYETHYLENE WALL THICKNESS: TANK WALL - .250" DIVIDER WALL - .19" LIQUID LEVEL 971 4 481 2 20" LID DIVIDER WALL OUTLET INLET 69 NORWESCO, INC. ST. BONIFACIUS, MN 1500 GALLON CAPACITY MAX. EARTH COVER 3.0 FT SERIAL NUMBER EMBOSSED HERE CAN BE REFERENCED TO THE DATE OF MANUFACTURE 4" INLET1 11 20 3 81 2 4" DIAMETER PASS-THROUGH HOLE IN PARTITION 233 4 1571 4 (external dimension) 1563 4 (internal dimension) 11 14 2 26 OPERATING VOLUME: PRIMARY COMPARTMENT: 1006 GALLONS OPERATING VOLUME: SECONADARY COMPARTMENT: 498 GALLONS CT APPROVED EFFLUENT FILTER 4043 Tough Problem Providing a simple, reliable, and permanent means for dividing septic tank effluent flow. TUF-TITE Solution A strong, stable, permanent, non-corrosive Tuf-Tite Distribution Box, with a Tuf-Tite Speed Leveler in each outlet. Snap-in pipe seals They’re patented. Simply insert your PVC pipe and push it through the flexible, polyethylene Tuf-Tite seal. Pipes fit watertight. Installation couldn’t be easier. Tuf-Tite® Distribution Box. THE TOUGH ONE! n Injection molded HDPE n Non-corrosive n Simple to install n Easy to level In a septic environment, no other material can match High Density Polyethylene in delivering a lifetime of trouble-free service. Tuf-Tite Distribution Boxes are injection molded, using only premium HDPE which contains no fillers or foam. They’re permanent Unlike cement-based pipe grout, Tuf-Tite seals will not crack or corrode in septic conditions. They stay pliable and watertight permanently. 4-Hole Distribution Box 4-Hole Dist Cat Sheet 11/8/01 8:09 AM Page 1 nInjection molded. Exceptionally strong. nHDPE is non- corrosive in a septic environment. nPatented snap-in pipe seals simplify installation. Interlocking Lid. Heavy-duty HDPE Lid is ribbed for added strength and rigidity. Slotted sides interlock on the Distribution Box to assure a tight fit. The 4HD2 Distribution Box comes complete with a Regular Lid or an Inspection Port Lid, and 5 snap-in fittings of your choice. Model B1 Riser. For series B1 Box. Stackable HDPE Risers extend to grade in 6” increments. Accept 11” x 11” lids and grates. 11” S-35 S-40 P-10 11” 11” 11” 11” 151/2” 2” Drop INSTALLATION IS JUST THIS SIMPLE 1.Position the Distribution Box on level virgin soil. Do not place box on a concrete slab. 2.Install the inlet pipe and outlet pipes. Be sure the bottoms of all pipes rest on virgin soil. 3.Level the Distribution Box and all pipes as needed. 4.Backfill the pipes to within two feet of the Distribution Box. Recheck the level of the box, then backfill up to the top lid ridge. 5.Install and adjust Tuf-Tite Speed Levelers. 6.Place lid on the Distribution Box and finish backfilling. Choice of Fittings S-35 Pipe Seal, for: n Sewer and Drain n SDR 35 n ASTM 3034 n Thin Wall n 1500 Lb. Crush S-40 Pipe Seal, for: n Schedule 40 n 4” Corrugated P-10 Plug, for unused holes Choice of Lids Regular Lid. Molded of rugged HDPE. Inspection Port Lid. For easy access and inspection. Models available to accept either 4” or 6” extension pipes. Tuf-Tite Speed Levelers™ Control the flow of effluent from the Distribution Box. Simply insert a Speed Leveler into each outlet pipe. Rotate each Speed Leveler so the flow is distributed as desired. Available for 3” or 4” PVC pipe. ©1999 Tuf-Tite® Corporation Form 4HD2-3. Printed in USA A full line of innovations for better septic systems 11” 6” 7” 14” Drainage and Septic Products Tuf-Tite®Corporation 1200 Flex Court Lake Zurich, Illinois 60047 4-Hole Distribution Box 4HD2 4-Hole Dist Cat Sheet 11/8/01 8:09 AM Page 2