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Home My WebLink AboutOWTS Report 01.02.2026500 Sweetwater Road, Garfield County, Colorado January 2, 2026 OWTS Report 1 Onsite Wastewater Treatment System Report 500 Sweetwater Road Garfield County, CO January 2, 2026 Prepared by Drew Wharton, P.E. drewdwharton@gmail.com (404) 643-8509 500 Sweetwater Road Gypsum, CO 81637 500 Sweetwater Road, Garfield County, Colorado January 2, 2026 OWTS Report 1 Table of Contents 1.0 Existing Conditions ........................................................................................................3 2.0 OWTS Overview ..............................................................................................................4 3.0 Maintenance....................................................................................................................6 500 Sweetwater Road, Garfield County, Colorado January 2, 2026 OWTS Report 3 1.0 Existing Conditions 1.1 General The site is located at 500 Sweetwater Road in Garfield County, Parcel # 186323100032. The site currently has a 2-bedroom residence onsite and an existing OWTS. A 1,250 2-chamber septic tank was installed in 2018 to county standards but tied into the houses’ original “drywell.” The property has an existing well for potable water at the northeastern corner of the property. An existing irrigation ditch runs along the middle of the property from west to east and Sweetwater Creek runs along the south property line. The original “drywell” leach field was discovered at the time of regular pumping of the septic tank. The existing gravel trench is currently less than nine feet and upslope of the irrigation ditch. 1.2 Soil Conditions Figure 1 – Vicinity Ma Profile pits were hand dug on January 1, 2026, and observed by Drew Wharton P.E.. The pits generally consisted of about 2 to 4 inches of topsoil, and then from there down, loamy sand and slightly moist soil to a depth of 3 feet. No free water was encountered during excavation. The pits were consistent with other soils on the site. A photo of the typical profile is shown below. No groundwater was encountered. Bedrock was not found. SITE 500 Sweetwater Road, Garfield County, Colorado January 2, 2026 OWTS Report 4 Typical OWTS Profile Pit and Soil Test Soil samples of the native material were taken from the soil profile pits, so gradation testing could be performed. The soil passing the No. 10 sieve was tested according to the USDA NRCS Guide to Texture by Feel. The results showed the soil was a Loamy Sand (Type 1) since it remained in a ball when squeezed and would not form a ribbon. Given this soil type and an effluent treatment Level of 1, Table 10-1 of the Garfield County On-Site Wastewater Treatment System Regulations indicates the LTAR (Long Term Acceptance Rate) shall be 0.8 gallons per day per square foot. 2.0 OWTS Overview The STA will be repaired in accordance with the Colorado Department of Public Health and Environment’s (CDPHE) Regulation 43 and Garfield County regulations. A Colorado Department of Public Health and Environment (CDPHE) permit is not required for a system of this size. Since only the STA is being repaired, a Major Repair Permit is required. Per Garfield County standards, a repaired STA can be within physical setbacks if it is no closer than the original, per Garfield County OWTS standards Section 43.4.6.b. The proposed STA is at a minimum ten feet from the irrigation ditch while the original is less than nine. The proposed will be downslope of the ditch while the existing is upslope. All other setbacks are met. The wastewater design flows were calculated using section 43.6 of the Garfield County On-site Wastewater Treatment System Regulations. The design flow used per person is 75 gallons per day. The assumed number of persons per bed is two for design purposes. These daily flows were used along with Section 43.7 to determine the minimum distances between components of the OWTS and the proposed well and surface water features. The existing 1,250 gallon Septic tank will be used to bring the effluent to Treatment Level 1 (TL1). 500 Sweetwater Road, Garfield County, Colorado January 2, 2026 OWTS Report 5 The required soil treatment area (STA) was determined by section 43.10 of the Garfield County On-site Wastewater Treatment System Regulations. 2.1 Design Flow The septic field will treat wastewater from the main residence. The residence currently has two bedrooms, but the STA was designed for three. Garfield County regulations require the design flow to include two people per bed with each person generating 75 gallons per day. - 3 beds x 2 people x 75 gallons per day = 450 gallons per day 2.2 Septic Tank Sizing For 3 beds, the minimum tank size according to the regulations is 1,000 gallons. The existing tank is 1,250 gallons. This septic tank will bring the effluent to Treatment Level 1 (TL1) before it flows to the soil treatment area. 2.3 Soil Treatment Area Sizing Using the design flow of 450 gallons per day and the LTAR of 0.8 gallons per day per square foot, it was determined that the minimum STA is 393.75 square feet for trench configurations. A 0.7 reduction factor has also been applied as chamber trenches shall be utilized. 33 Quick 4 Plus Low-Profile infiltrators will be arranged in 2 trenches. One trench will have 16 infiltrators and the other will have 17. Each trench does not exceed the maximum width of 3 feet and will be spaced 4 feet from each other. The chambers will be installed between 2 and four feet deep. 2.4 Setbacks According to Table 7-1 of the Garfield County OWTS Regulations the soil treatment area must be a minimum of 100 feet away from the proposed well and 50 feet from surface water. The STA has been positioned to meet all setbacks except the setback from the irrigation ditch. The septic tank and sewer lines also meet the required setbacks. Per Garfield County standards, a repaired STA can be within physical setbacks if it is no closer than the original, per Garfield County OWTS standards Section 43.4.6.b. The proposed STA is at a minimum ten feet from the irrigation ditch while the original is less than nine. 2.5 Distribution and Dosing The soil treatment area will be gravity fed via 4” schedule 40 pipe. The distribution pipe running up to the distribution box is sloped toward the STA at a minimum of 1.0%, done to prevent freezing and eliminate stagnant fluid sitting in the line. From the distribution box to the chambers, to 4” pipe will be flat. All chambers will be installed on a level surface. The distribution pipe will be encased at the irrigation ditch crossing. Endcaps and inspection ports will be installed a the end of each trench. 500 Sweetwater Road, Garfield County, Colorado January 2, 2026 OWTS Report 6 Maintenance The Owner will follow the operation and maintenance required by Section Garfield County On- site Wastewater Treatment System Regulations. Below is a maintenance schedule for the OWTS. Maintenance and Cleaning Frequency Type of Component Inspection/Maintenance Cleaned or Pumped Septic Tanks Every 2 Years Every 2 Years, or As Needed Absorption Areas Every 6 Months N.A.