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Home My WebLink AboutOWTS Design www.sgm-inc.com GLENWOOD SPRINGS 118 West Sixth St, Suite 200 | Glenwood Springs, CO 81601 | 970.945.1004 Page | 1 August 16, 2022 Mr. Ted White, Environmental Health Specialist III Garfield County Public Health 2014 Blake Avenue Glenwood Springs, CO 81601 RE: Glenwood Electric Operations OWTS 1777 CR 241 East Elk Creek Road New Castle, CO 81647 Dear Ted, The purpose of this letter is to provide you soils and design information relative to a tactile soils analysis that SGM has performed on behalf of the City of Glenwood Springs in support of the installation of an OWTS on the proposed soil treatment areas located on their property located along Deveroux Road. The property is located per the following: Test Hole Locations 1660 DEVEROUX ROAD www.sgm-inc.com GLENWOOD SPRINGS 118 West Sixth St, Suite 200 | Glenwood Springs, CO 81601 | 970.945.1004 Page | 2 This report and design provides the City’s contractor, Gould Construction, the direction for which he can construct an OWTS for the lot considering the development of an OWTS for the Electric Operations Facility proposed. On the drawings attached at the end of this report, you will see the necessary OWTS components for the described situation. From the NRCS Websoil Survey, the on-site soils (for the STA) are identified as a Begay Sandy Loam. The on-site observations of the Begay Sandy loam were characteristic of the sandy loam identified in the WebSoil Survey. Our findings of the soil concur with those characteristics identified by NRCS in their soil investigation for the Websoil information. Specifically, our findings are as follows: 1. Depth to ground water is greater than 8 feet. 2. Depth to limiting layer is greater than 8 feet. 3. Other than a limited depth of topsoil, the soil horizon(s) below the topsoil is a consistent sandy loam soil meeting the characteristics of the Soil Type 2A in Table 10-1 of Regulation 43 from CDPHE. 4. The soil structure grade was a moderate structure. 5. The No. 10 sieve and smaller particles had a blocky/granular soil structure. 6. The sample contained less than 35% rock. 7. The ribbon size from tactile analysis revealed a less than 1 inch ribbon with neither a gritty or smooth texture. 8. Given these results, the classification for these soils is a Sandy Loam, or as previously stated, a Type 2A Soil per Regulation 43 Table 10-1. (GARCO Table 10-1) 9. The depth of this soil layer is in excess of 8 feet with no groundwater. The proposed OWTS for the facility will consist of a 1,000 gallon septic tank for 12 full time employees (ADF= 420 gpd at 35 gpd per employee) discharging by gravity flow from the second compartment to a 500 gallon dosing tank with an Orenco pump. From the dosing tank, the supernatant will be pumped to an automatic distributing valve which will alternate flow between four 3x40’ chambered trench systems. These facilities will be located on east side of the property, in excess of 25 feet from an adjacent dry gulch. The chambered trenches will be pressure dosed with the distribution media being Infiltrator Quick4 chambers. The system has been sized for the Type 2A soils from a loading rate perspective. · The soil tactile analysis reveals a Type 2A soil which is reflective of percolation rates of 25-40 mpi. The loading rate for the Type 2A soil and TL1 is 0.50 gallons/sf/day. · We are recommending constructing the STA in the Begay sandy loam located just east of the building site. This will accommodate a gravity system to the septic and dosing tanks. www.sgm-inc.com GLENWOOD SPRINGS 118 West Sixth St, Suite 200 | Glenwood Springs, CO 81601 | 970.945.1004 Page | 3 Note that the drawing package is prepared in a semi-schematic format that relies on the contractor/owner to provide adequate grading to accomplish the intent of the design. In this manner, it is anticipated that the contractor/owner can provide routing modifications to make sure that the grading works for the site. Note that the component construction for the system will need to follow the requirements of Sections 43.8, 43.9 and 43.10 of regulation 43 (as adopted by Garfield County) for the tank, dosing tank, pump, piping and STA as applicable. We have attached a copy of each of these sections for reference by the contractor/owner to assure each component construction is adequately addressed. Upon your receipt and review, if you have any questions, please don’t hesitate to call. Respectfully, SGM Jefferey S. Simonson, PE, CFM Principal 8/16/22 Client:City of Glenwood Springs Project Location:Deveroux Drive Electric Operations Center Glenwood Springs, CO Glenwood Springs, Colorado 81601 Date:12-Mar-20 Flow Data for the OWTS Design 1 Full Time Employees=12 420 (based on 35 gallons per capita per day and an 8 hour shift) Total=420 Totals:420 gpd Soil Data for the OWTS 2 Data from NRCS Websoil observations:Appears to be a sandy loam soil of consistent SOIL TYPE 2A depth from surface beyond a depth of 8 feet where the depth where the NRCS profile pit was excavated. At a depth of 8', neither bedrock or groundwater are expected to be encountered. Data from the web soil survey indicates a Begay Sandy Loam exists. Textural Triangle Data: % Clay 12.5 % % Sand 67.9 % % Silt 19.6 % Tactile soil evaluation at time of construction to be performed to collaborate the NRCS Websoil data assuring the sandy clay loam is present and depth to limiting layer is > 8 feet Given the consideration of all data, the Long Term Acceptance Rate to use is 0.50 gallons/sf/day for treatment level 1 (TL1) Septic Tank Sizing 3 Flow calculated from above:420 gpd 48 hour detention time for septic tank sizing;Volume= 840 gpd Install a 1,000 gallon tank. Sizing of Absorption Field or Soil Treatment Area 5 Going with a soil type 2A and Treatment Level 1, LTAR = 0.5 g/sf/d For a pressure dosed system, size adjustment factor is 1.0 for a bed configuration (Yes) For a gravity system, the size adjustment factor shall be 1.2 for a bed configuration For a gravity trench system, adjustment factor = 1.0 For a pressure dosed trench system, adjustment factor = 0.8 For use of chambers: size adustment factor is 0.7 (YES) STA= Flow/LTAR 840 square feet (unfactored) For a chamber system, adjust size to 0.7*840= 588 square feet For pressure dosed trench system, adjust size to 0.8*588=470 square feet For a chamber system in a trench configuration, length=157 feet (this would equate to 2 runs of 75.5 feet each) With the effective length of a Quick4 chamber at 4', use 19 chambers per trench for two trenches (Alternative - install 4 trenches @ 40 feet long, 10 per trench - total 40) (total min. length of each trench is thus 76 feet long for two trenches) For a bed system: Go with 1 bed, 12' wide, pressure dosed. Length of bed=49 -(say 50') Number of chambers for bed:52 chambers OWTS Design Report and Calculations Figure 2- Profile Hole #1 Figure 1A- Profile Hole #1 Spoil Pile Figure 2- Profile Hole #2 Soil Testing for City of Glenwood Spring, Electric Operations Center OWTS Deveroux Road, Glenwood Springs, Colorado Photo Documentation Date: 2/29/2020 Figure 1B- Profile Hole #1 Figure 2A- Profile Hole #2 Figure 2B- Profile Hole #2 Figure 3- Sample from Profile Hole #1 Figure 4- Profile Hole #1 Ribbon Break < 1" Figure 5- Profile Hole #2 Sample Figure 6- Profile #2 Ribbon Break Slightly < 1" *···NET NET WEIGHT CAPACITY LID TANK TOTAL 1,042 GAL. 2,620 LBS 8,915 LBS 11,535 LBS DIGGING SPECS INVERT DIMENSIONS···· DIGGING SPECS INVERT DIMENSIONS NET NET WEIGHT CAPACITY LID TANK TOTALGraphic ScaleIn Feet: 1" = 20'0102040Title:OWTS Plan(Trench Alternate)Revision#Dwg No.Glenwood Springs Electrical Operations Headquarters Garfield County, ColoradoJob No.Drawn by:Date:File:PE:QC:2013-493TBS06-02-2022RLBGWS-ESO-OwtsPlan-trench alternJSS118 West Sixth Street, Suite 200 Glenwood Springs, CO 81601 970.945.1004 www.sgm-inc.com Date By:C12A #Of :######################Project Milestone:8/12/22