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HomeMy WebLinkAboutOWTS ReportSeptember 15, 2022 502 Main Street • Suite A3 • Carbondale, CO 81623 • (970) 704 -0311• Fax (970) 704 -0313 S OPRIS E NGINEERING • LLC civil consultants Steve Beckley Paqarina Ranch LLC 581 CR 241 New Castle CO 81647 "Steve Beckley" <sbeckley@glenwoodcaverns.com> RE: OWTS-3 Design Report- Elk Creek Campground –South Area 3, 581 County Rd 241, New Castle, Garfield County, Colorado. SE Job No. 232101.01, Parcel Number: 212524300013 and 212524300019 Dear Steve: This letter report presents the applicable findings in regard to the design and construction of an Onsite Wastewater Treatment System (OWTS) to serve a select portion of the existing campground located south and west of East Elk Creek, at the above referenced site. The subject portion of the campground has 14 spaces with electric, water and sanitary hookups in place but has not been inactive for several years. The sanitary hookups have been locked and no sewer service has been available to these particular sites. The existing sanitary, water and electric service hookups were installed by previous owners of the campground. The proposed OWTS improvements to serve these select spaces include confirmation of continuity and integrity of existing sewer service collection pipes and hookups, installation of new septic detention tanks, effluent dosing assembly, installation of advanced Treatment level 3N system components and installation of new pressure dosed soil treatment area (STA) dispersal systems. These OWTS improvements are designed for the exclusive use of the designated camp ground area and spaces noted above. The balance of the campground north and east of East Elk Creek is in operation and served by separate OWTS under previous Garfield County Septic Permits, (Number: Sept-8-09-1189) issued on August 3, 2009 and No. 1032, issued 1981. Findings The OWTS components to serve the select campsite are designed and situated in designated locations that are suitable per the provisions of the Garfield County OWTS regulations to provide effective treatment of the estimated design flow. The proposed engineered OWTS have been designed based on the site assessment findings that included relevant review of physical, legal, regulatory, existing and proposed conditions. The system treatment components have been designed and specified in coordination with Roger Schafer of SCG Enterprises, Inc. that will supply the advanced treatment, STA, tanks and appurtenances for the new system. The OWTS will be constructed in accordance with applicable engineering criteria and regulatory compliance. The proposed site specific improvements are presented on the attached civil site and OWTS design plans for obtaining a County OWTS construction permit. The design and construction recommendations with specifications and details are delineated on the civil design plans, C1-OWTS Site Plan, C2 -OWTS Systems Plan, C3-OWTS Details, dated 09-15-22, by Sopris Engineering. Steve Beckley Paqarina Ranch LLC SE Job No. 2532101.01 September 15, 2022 Page 2 Site Location The subject site is located along East Elk Creek northwest of the Town of New Castle at 581 County Rd 241 (East Elk Creek Road), on the Paqarina Ranch properties. The site is situated in Section: 24 Township: 5 Range: 91. The entire Paqarina Ranch properties comprise approximately 120 acres. The select portion of the existing camp ground and designated areas for OWTS improvements comprise approximately 1.4 acres that includes the limited OWTS service area. The subject portion of the site is bounded on the north and east by East Elk Creek and on the south and west by undeveloped land. Existing Site Conditions The campground is on relatively flat ground along East Elk Creek west of County Road 241. The proposed STA and advanced treatment components envelope is on variable southeast facing sloping terrain to the trending toward the southeast at 10% to 20% situated over 100 feet horizontally and 40 to70 feet vertically from the creek embankment. The proposed primary septic detention tanks will be 50 feet from the creek high water line. Existing gravel driveway provides access to the proposed detention tanks and an existing dirt road provides access to the advanced treatment components. The developed and undeveloped portions of the site has existing vegetation consisting of sagebrush, oak brush, grasses, shrubs scattered aspen and spruce trees. The subject service area is accessed off CR 241 from the main campground across an existing bridge to the south. Existing water service is supplied by a well and associated storage tanks (CDWR Permit # 45991),decreed in water Court case No. W-1143. Proposed Site Conditions The OWTS will serve 14 RV campsite spaces. The proposed improvements will include a new OWTS system with associated minor grading, pipeline and electrical trench excavating. The site has existing electric and water services. Buried Electric service lines will be extended to the OWTS component areas. The new owners and operators are engaged in comprehensive master planning for the existing facilities on the properties. The short term future (within 5 years) goal is to consolidate existing and proposed usage for sewage collection, conveyance and treatment under a state permitted WWTW with applicable discharge permit. Therefore the proposed OWTS improvements are considered temporary to allow the full use of the existing campground facilities not currently served by existing OWTS systems. In the future the new components installed will be repurposed for use in the overall consolidated system. OWTS Summary The OWTS design is based on our evaluation of the hydraulic usage, soil characterization, strength of wastewater, existing and proposed site conditions with respect to the operation and installation of a new OWTS in accordance with Garfield County OWTS Regulations and State of Colorado Regulation 43. The design includes three 1500-gallon septic tanks for primary detention, with a high head pump assembly to transport septic tank effluent to the upper treatment and dispersal works. The Advanced treatment components consist of a 1500 gallon treatment tank equipped with Orenco Systems Advantex-AX-100 treatment unit and control components to provide advanced secondary treatment of the septic tank effluent providing for treatment level 3n effluent quality. The treated effluent will gravity discharge to a 500-gallon pump basin tank to be equally pressure distributed across a Geoflow drip tubing dispersal field system. The soil dispersal Steve Beckley Paqarina Ranch LLC SE Job No. 2532101.01 September 15, 2022 Page 3 system shall consist of an array of Geoflow looped dripline laterals installed in shallow plowed slits in the general area delineated on the plan. The treated effluent will be discharged from the tank pump basin through an engineered headworks assembly for equal pressure distribution, at a controlled flow rate, across the entire drip tubing dispersal field. The Geo flow system is designed based on the design flow rate and the soil infiltration acceptance rate determined by the soil’s long term acceptance rate (LTAR) for treatment level 1 to account for peak surge volumes. The dispersal system is designed to frequently dose small quantities of treated effluent to the shallow soils well below the soils saturation point. The system will meet all required setbacks and be installed with respect to maintaining existing vegetation within the general boundaries indicated on the plan. The treatment system will include all controls and Vericom telemetry. The system will be maintained and serviced on a bi-annual basis by a qualified service provider. The design criteria is outlined below and delineated on the attached site plan. Treatment System Criteria Design of the site’s OWTS is in accordance with EPA design recommendations and requirements for secondary wastewater treatment. The design includes the installation of an Orenco Systems, Inc., Advantex treatment system and a Geoflow dispersal/infiltration field for the absorption and polishing of treated effluent in the shallow soil. The site specific OWTS has been designed as a full pressure dosed system and will be constructed to achieve treatment level 3 (TL3) in compliance with the provisions of Regulation 43, Section 43.6, B and with respect to the included Tables 6-3 and 6-4. Horizontal distances from the various components of a system to pertinent site features, including water courses, wells, dwellings and property lines, are in accordance with Regulation 43, Section 43.7, and the setback distance indicated in Tables 7-1 and 7-2 for treatment level 3N. The OWTS is designed with specified components to be installed and constructed in accordance with the provisions in Regulation 43 covering general design criteria, Section 43.8, component design criteria, Section 43.9, soil treatment area, Section 43.10 . and Design Criteria – Higher Level Treatment Systems, Section 43.11. The engineered system is designed for a minimum 1400 gpd capacity utilizing an advanced secondary treatment system, however the AX treatment components and enlarged STA dispersal field is sized to treat up to a peak flow of 2500 gpd. The specified secondary treatment unit is an Orenco Systems Advantex-AX-100 recirculating pack bed filter system that has the capacity to treat effluent from an equivalent 15-bedroom residence. All OWTS components will be accessible from the surface to facilitate system testing and maintenance. The OWTS inspections, monitoring, maintenance requirements, record drawings and certification letter will be performed accordance with Regulation 43 Applicability, Section 43.4 and Operation and Maintenance Section 43.14. Design Calculations OWTS Installation of an OWTS with a minimum 1400 gallon capacity to meet TL3N effluent quality. Per effective County Regulation 43 Design Criteria: Minimum design flow is based on 14 RV spaces. Gallons per day per space =100 gal/space/day, no peaking factor Design Maximum Daily Flow (Qd)gallons/day = (# of spaces) x (avg.daily flow)gal/spaces/day. Steve Beckley Paqarina Ranch LLC SE Job No. 2532101.01 September 15, 2022 Page 4 Design Maximum Daily Flow Qd = 14*100=1,400 gpd Design Average Daily Flow Qavg is estimated to be 700 gpd The wastewater strength is assumed to be 300 mg/L as compared to residential strength of 180 mg/L The organic loading rate is assumed to be 3.36lbs BOD5/day based on table 6.2 values. The increased septic detention capacity and Advantex treatment system will reduce the biological mass loading up to 95% to TL-1 effluent discharge quality. Mass loading per QD= 1400 gpd x 300 mg/L x 0.00000834= 3.5028 lbsBOD/day The 300 mg/L X 0.5=15 mg/L equating to 0.03 lbs/day discharge to the STA Septic Tank Design The septic tank capacity required for a minimum HTR of 2.5 hours for commercial higher strength waste hour retention time is calculated as follows: V = 1400 gal/day * 3 = 4200 gallons. Install 3 new 1,500 gallon 2-compartment fiberglass/septic tanks in series to provide a total of 4500 gallon detention capacity. The second compartment of the third tank will be installed with an Orenco Systems PVPM bio tube with high head dosing pump to transport septic tank effluent to the treatment work for additional secondary treatment. The dosing system controls will be set up for incremental timed dosing with residual storage in the pump basin to allow adequate detention time between doses and attenuate peak loading. Secondary Treatment works Design The AX-100 Pod is rated to treat up 2500 gal per day of residential strength waste water or up to 4.0 lbBOD/day. Based on the assumed waste concentration of 300 mg/L the total mass loading based on 1400 gpd is 3.5028 lbsBOD/day. Therefore the AX-100 is sized to adequately treat the design loading rate and infrequent peak loading rates. The geo flow dispersal field is sized to accommodate the design loading with sufficient area to disperse minimum dosing volumes during a day. Sub Surface Conditions and Testing A site specific subsurface soil evaluation was performed by Sopris Engineering on August 23, 2022. Two 8- feet deep profile pits and three shallow pits were excavated in the vicinity of the proposed OWTS field. The shallow soils in the location of the proposed Geo Flow dripline field were sampled and characterized by application of the USDA soil texture method test. The soils were tested to determine the hydraulic loading rate for treated effluent infiltration in the native soils. Based on site observations, the soils below 4 to 6 inches of topsoil consist of medium dense sandy silt loam texture soils to 5 feet overlying relatively dense, sandy silt loam with gravels and cobbles. This soil type 2 has an effective loading rate for conventional soil treatment of 0.6 gal/S.F./day for a level 1 conventional treatment system. Therefore for design purposes the soil underlying the proposed soil treatment area (STA) will be considered type 2. In order to provide optimal dispersal of treated effluent a pressure dosed STA utilizing 1/2 inch pressure compensating dripline tubing sized for a treatment level TL-1 system based on the design flow. No free water is expected to be encountered within the field excavations. Normal Groundwater levels are expected to be below 20 feet from the existing surface grades. The soil appears to be consistent in both profile excavations and across the site. Steve Beckley Paqarina Ranch LLC SE Job No. 2532101.01 September 15, 2022 Page 5 The native soils sampled from 1-2 below the surface are characterized as a soil type 2consisting of sandy silt loam texture with moderate granular structure. The tactile soil test ribbons were 3/4 to 1-inch long The type 2 soil has a theoretical effective loading rate for conventional soil treatment of 0.6Gal/S.F./day for a level 1 conventional treatment system. To provide optimal treatment to reduce the moderately strong RV waste an Orenco Systems Advantex AX-100 secondary treatment system is specified that will treat effluent to a Level 3N treatment quality prior to infiltration into the native soil via a full pressure dosed drip system designed based on a level 1 LTAR of 0.6Gal/S.F./day. The soils are suitable for the installation of a dripline system that will be fully pressure dosed and utilize GeoFlow pressure compensated 1/2" driplines with emitter on 2' centers. An construction inspections and direction will be performed during construction to confirm that the drip tubing is installed per design and the manufacturers recommendations. Geomat Drip System / Treated Effluent Dispersal System Design The tertiary treatment/absorption field is designed based on utilizing the effective Long Term Acceptance Rate (LTAR) for effluent meeting Treatment Level 3N quality utilizing pressure dosed Geo Flow dripline dispersal system installed in shallow native soil. Long Term Acceptance Rate (LTAR) Treatment Level 3N effluent dispersal system with a loading rate 1.1gal./S.F./day) for Type 2 receiving soils; For peak flow surge capacity the system will be sized based on Treatment Level 1 loading rate of 0.6 gal./S.F./day) for the Type 2 receiving soils. Loading factors L.F.; (Table 10-2, pressure dosed bed application = 1.0) A(sf) = Qd x L.F.: A = Area; Qd = flow (gal/day) = 1400 gpd LTAR L.F.1=1.0 pressure dosing LTAR = 0.6 gal/S.F./day for treatment level 1, Soil type 2 A(sf) = 1400 gpd x 1.0 = 2333 S.F. Utilizing advanced secondary treatment technology 0 .6 Install minimum 1,167 L.F. (Install 2000 L.F.) of Geo Flow PC 1/2" drip tubing to a minimum 8" and maximum 12" depth below finish grade in narrow plowed (ripped) 2-4 inch slit trenches spaced at minimum 2' separation. Install 16 looped dripline laterals with PC emitters every 2-feet. Each looped lateral will be approximately 50-80 feet long from their respective connections to the supply and return flow manifolds. The dripline field will be micro-dosed via the headworks assembly from the simplex high head distribution pump system installed in a 500 gallon dosing tank. The dosing system controls will be set up for demand dosing with residual storage in the pump basin to allow for full drainback of effluent in the the transport and distribution piping. The design dosing cycles per day is 12 based on the design flow and dispersal field sizing. Drip Dispersal System Design Criteria Geoflow’s WASTEELOW®’ drip system disperses effluent below the ground surface through 1/2” pressurized pipes. It is designed using minimum 2-feet grid concept with the drip line connected to supply and flush manifolds installed in a common trench creating a closed loop distribution lateral system. The tight emitter spacing design provides for the daily design flow discharge being distributed to promote a consistent subsurface wetted area. The objective with effluent dispersal is to disperse the effluent across the entire field Steve Beckley Paqarina Ranch LLC SE Job No. 2532101.01 September 15, 2022 Page 6 area as efficiently as possible with several micro dose cycles during the day at an approximately uniform rate throughout the year. Subsurface drip is a highly efficient method to allow absorption of treated effluent by applying small, precise amounts of treated effluent uniformly under the soil surface. A properly designed dripline tubing system will not result in soil saturation or surface puddling and can be used to mitigate site specific situations of high water tables, tight soils, rocky terrain and steep slopes. The drip tubing is flexible and can be installed around existing structures, large boulders, trees, vegetation, and other site features. It is effectively installed directly into indigenous soils without significant disturbance to maintain the natural landscape provide for rapid vegetated surface recovery. Geoflow Dripline Layout Design The Advantex treatment system installed with the new septic tank will gravity discharge treated effluent from the treatment pod to the 1000 gallon dosing tank. An Orenco bio-tube vault with a simplex high head effluent pump vault installed in the dosing tank is utilized to transport effluent from the pump basin to the Geoflow field. The treated effluent will be pressure dosed through a 1.5” discharge assembly to the Geoflow head works assembly consisting of the 1-inch PVC supply pipe and return flush pipe apparatus housed in a large valve box with risers and insulated lid at the surface adjacent to the tank. The pump will demand dose the treated effluent through the Geoflow head works assembly through the 1” supply line manifold and that connects to each Geoflow looped lateral. The looped lateral ends connect to a 1” return flow manifold to provide for continuous flushing and drain back. The dripline lateral connections shall be installed to provide a minimum 15" offset of the first and last emitter from the supply and return manifolds respectively. The 1" diameter manifolds will be installed at continuous slope down from the most up gradient lateral to the dosing tank to insure positive drain back through the supply and return manifolds. The return manifold invert shall be approximately 6" lower than the supply manifold. Air vacuum breakers will be installed at the high terminal ends of the manifold lines. The drip line laterals will be installed to insure optimal performance, installation efficiency and to preserve vegetation to the maximum extent possible in narrow (rip/plowed) trenches relatively level following the existing grade contours. The dripline laterals will be placed 8" to 12” deep within the native soil and backfilled immediately with the native soil. The length of each pressure compensating dripline looped lateral may vary, however the assumed length is approximately 60-80 lineal feet from their respective connections to the supply and return flow manifolds. The minimum separation distance between laterals is 2 feet however the separation distance may be varied based on vegetation, grades and other existing conditions within the field areas. Control Systems An Orenco systems control panel will be installed by a qualified installer in coordination with the electrician. The control panel will control all functions and monitoring of the installed treatment and distribution components. The controls will record all operational pump cycles, run times, operational conditions and is capable of making automatic adjustments as necessary. Operational floats and alarms for the treatment system components in the re-circulation septic tank vault and dosing basin will be recorded and reset by the Steve Beckley Paqarina Ranch LLC SE Job No. 2532101.01 September 15, 2022 Page 7 control panel. A Vericomm Telemetry system will be installed via a phone line connection in the control panel to allow offsite monitoring, data collection and remote operational setting control. The system is set up with a web-based technology for use by authorized operators and/or the contracted maintenance providers. The control panel will be configured for 110 volt electric service for to the pumps and controls. The power supply for the pumps and controls shall consist of (2) 20 amp circuits for the dosing and circulation pump and (1) 10-amp circuit for controls. Provide line of site disconnect at the control box to the pump and control components at the tank. The electrician or qualified installer shall install electrical wires in conduit from the service panel and or junction box to the Orenco control panel. Direct bury electrical wire may be used and installed in the gravity sewer trench from the control panel to the respective pump assembly exterior junction boxes mounted on the risers over the pump basin and treatment re-circulation tank. OWTS Operation and Maintenance All components of the engineered OWTS should be inspected on a regular basis and be properly maintained. The responsibility for repair and maintenance of the system will remain with the Lot Owner. The owner will retain the services of a qualified service provider to inspect the OWTS and to perform all required maintenance and repairs to ensure that the system is in good operating condition in compliance with the manufacturer’s performance requirements. The operating components of the OWTS system will be inspected within 30 days of being placed into operation and thereafter inspected and serviced every six months in accordance with Regulation 43 Applicability, Section 43.4 and Operation and Maintenance Section 43.14. The treatment system supplied by SCG will be purchased by the owner with a minimum 3-year maintenance contract. A clearly visible, permanently attached label or plate giving instructions for obtaining service must be placed at a conspicuous location for a higher level treatment system with applicable components under a service contract. The owner is responsible for maintaining a contract with a qualified service provider to ensure compliance with the provisions of the Garfield County OWTS Regulations, any permit conditions and the manufacturer’s system maintenance protocols. Construction and Inspections Prior to construction of the permitted system, the engineer should be contacted by the contractor and construction project manager well in advance to provide adequate time to discuss the system components with the contractor, answer questions, resolve any conflict issues and schedule inspection site visits based on construction progress. A pre-OWTS construction meeting and calls are essential and required prior to installation of the OWTS components. The engineer, prior to excavation shall inspect the staked location, of the proposed treatment/absorption bed and tank. All septic system components shall be staked in the field for approval by the Engineer prior to excavation. During initial construction the engineer will evaluate the soils in the location of the absorption treatment field to confirm design assumptions made and existing conditions. The engineer will provide construction recommendations and make adjustments to the field layout and sizing if needed with discussion of construction procedures.