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HomeMy WebLinkAboutOWTS Design 01.03.2020Huddleston-Berry Engineering & Testing, LLC United Companies PO Box 3609 Grand Junction, Colorado 81502 Attention: Mr. Robert Lewis Subject: OWTS Design New Batch Plant Rifle, Colorado 2789 Riverside Parkway Grand Junction, Colorado 81501 Phone: 970-255-8005 Info@huddlestonberry.com January 3, 2020 Project#00256-0079 Reference: Foundation Recommendations, New Batch Plant, Rifle, Colorado by Huddleston- Berry Engineering & Testing, LLC for United Companies, October 28, 2019. Dear Mr. Lewis, At your request, Huddleston-Berry Engineering & Testing, LLC completed design of an Onsite Wastewater Treatment System (OWTS) for a new concrete batch plant in Rifle, Colorado. The site location is shown on Figure 1 — Site Location Map. A site plan is included as Figure 2. Subsurface Investigation As discussed in the referenced report, the soils at the site consisted of sandy gravel and cobble (pit -run) materials. Groundwater was observed in the excavation at a depth of approximately eight feet at the time of the investigation. Onsite Wastewater Treatment System Seepage Bed Design The design of the absorption system follows the requirements of the Garfield County On -Site Wastewater Treatment System (OWTS) Regulations, Adopted June 2018. Due to site constraints, a conventional OWTS with a soil treatment area is not possible. As a result, a vault system is proposed. Based upon information provided to HBET, no more than twelve employees will be working at the facility during a single shift. No showers will be provided at the facility. The daily flow of the OWTS is calculated below. Average Industrial Daily Flow = (12 employees/shift)(1 shift)(20 GPD/person) = 240 GPD HBET understands that a commercially available 1,500 gallon tank is proposed. A 1,500 gallon tank will provide for approximately six days of storage capacity. In accordance with the regulations, a visual and/or audible signal must be provided indicating when the tank has been filled to 75% of its capacity. Rifle Batch Plant #00256-0079 01/03/20 Huddleston-Berry Engineering& Testing, LLC In addition, HBET understands that the tank is proposed to be placed in an automobile parking area. The concrete tank is not traffic rated. In order to accommodate vehicular loading, HBET recommends that a 6-inch thick reinforced concrete slab be placed above the tank. System Installation The installation of the septic tank and effluent lines should be completed in accordance with the Garfield County On -Site Wastewater Treatment System (OWTS) Regulations. In addition, the following construction procedures are recommended: • The septic tank should be placed level over native soils that have been scarified to a depth of 8 to 12 inches, moisture conditioned, and recompacted to a minimum of 95% of the standard Proctor maximum dry density, within ±2% of optimum moisture content. However, up to 3-inches of washed rock or pipe bedding passing the 1-inch sieve may be used as a leveling course under the septic tank. • The bottoms of trenches and backfill around the septic tank which will support sewer or effluent lines should be compacted to at least 90 percent of the standard Proctor maximum dry density, within ±2% of optimum moisture content. Pipe bedding should have a maximum particle size of 1-inch. Inspection Schedule Huddleston-Berry Engineering & Testing LLC should be retained to monitor the construction of the OWTS. The following schedule of observation and/or testing should be followed: ■ Observe placement of the septic tank and all connecting sewer and effluent lines prior to backfill. Verify proper fall between inverts. In conformance with Garfield County regulations, HBET will be required to provide Garfield County with documentation certifying that the OWTS was placed in conformance to the plan and Garfield County regulations. General Notes The OWTS design was based upon the results of the subsurface investigation, information provided to HBET, and on our local experience. The design is valid only for the proposed construction We are pleased to be of service to your project. Please contact us if you have any questions or comments regarding the contents of this report. Respectfully Submitted: Huddleston-Berry Engineering and Testing, LLC Michael A. Berry, P.E. Vice President of Engineering C:\HBET\Project Files\2019\00256-0079 Rifle Plant\200 - Geo\00256-0079 LR010320.doc 2 FIGURES Go gle Earth mikl ems 1 1 A SCALE: 1" = 100' (ON 11 X 17) cP FLY ASH SILO BATCH \ OFFICE SCALE OFFICE t a E \age Wfault RIAC PLANT ^141'_--1— r r— r— Project No.: 00256-0079 Date: 01/03/20 By: MAB "NM mot ,A16. Huddleston-Berry Engineering & Testing, LLC 2789 Riverside Parkway Grand Junction, CO 81501 UNITED RIFLE PLANT PARCELS 217711300450 AND 217711300451 FIGURE 2 - SITE PLAN