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Home My WebLink AboutOWTS Installation Observations 11.24.2021November 24, 2Q21 Haines, Steven G & Bailey A 18 Pine Street, Carbondale Co 81623 "Steven Haines" Eoffgridsteve@gnail.com3 RE: Design Report, On -site Wastewater Treatment System (OWTS), 41 S. Pine Drive, Carbondale, Garfield County, CO, Copperton Townsite Block: 13 Lot: 5 Amended Lots 5-9 SE Job No. 31132, Parcel No: 239328313016, Garfield County E14D Permit # SEPT-6929, Acceptance 08-03-21 Dear Steven: Pursuant to County requirements, this letter provides documentation that the Onsite Wastewater Treatment System (OWTS) upgraded components recently installed at the above referenced site is in compliance with the permitted design. Sopris Engineering inspected the excavations, soils, materials and the installation of the system components during construction, prior to final backfill and after all installations were completed. The replacement absorption field and pump dosing/ distribution component installations were designed and constructed to serve the proposed usage on the subject property. Sopris Engineering performed site visits to inspect and document the as -constructed conditions of the OWTS. Inspections were coordinated with the property owner that installed the system components. The as -constructed conditions and installation of the new OWTS components is in compliance with Garfield County Regulations; the recommendations and specifications delineated on the civil design plans, C1-OWTS Plan revision dated 6-23-2021, and the OWTS design Report dated 6-23-21, by Sopris Engineering. The design criteria and system sizing information is summarized below. WTS Desivn Criteria and Sizin Based on our findings the design and installation of an engineered OWTS with enhanced treatment is feasible in accordance with applicable County and the State of Colorado Regulation 43. The existing residential structure has 4 bedroorns. The system is designed based on the current County design criteria and was constructed to provide for demand dosing of septic tank effluent to an engineered enhanced media soil treatment area (STA) utilizing Geomatrix System, LLC "Geomat" system approved by CDPHE for use as a proprietary distribution product. The design is in compliance with the current County Regulation No. 43 per a minimum equivalent 4-bedroom residential design flow capacity with area calculations based on the LTAR loading rate for the in -situ soils utilizing applicable multiplier loading rates for enhanced manufactured media. Geomat material is installed over a 6-inch layer of ASTM-33 filter sand in shallow pressure dosed beds. The OWTS maintains the gravity service pipe from the existing dwelling to the existing 1,500-gal concrete 2-compartment plastic septic tank. The replacement system includes the installation of a new 30" ribbed PVC riser Pump basin in series with the primary tank that provides for a minimum 45 gallon dosing volume and minimum 150 gallon storage volume. The dosing basin is equipped with an Orenco System simplex high head effluent pump assembly for pressure distribution to the Geotextile Sand filter (GSF) bed's custom perforated distribution laterals. The pump is installed in a high head pump flow inducer (UF1) assembly wl float tree, bracket & mounting flange wl the specified P300511 pump. The effluent discharge piping is installed to connect to a common manifold pipe that connects to the custom perforated distribution laterals at the head of the Geomat treatment/absorption beds. Desien Calculations OWT Design population is 3 bedrooms x 2 persons + 1 bedroom x 1 person = 7 persons total. Gallons per day per person =75 gal/person/day, No peaking. factor Design capacity = Max. Design flow (Qd)gallonslday = (# of people) x (avg. flow)gallpersonlday. Design flow Qd = 7 + 75 = 525 gpd Septic Tank Design: 2-Day detention time = 525 x 2 = 1,050 gallons required. 502 Main Street • Suite A3 • Carbondale, 00 81623 • (970) 704-0311 - Fax (970) 704-0313 SOPRIS ENGINEERING * LLC civil consultants OWTS As Constructed Certification 41 S. Pine, Carbondale SE Job No. 31132.01 November 24, 2021 Page 2 Continue use of the existing 1,500 gallon plastic two -compartment primary septic tank and installed in series a 150 gallon pump basin with a simplex high head pump dosing assembly. Sub Surface Conditions and TestinE A subsurface soil investigation and site assessment was performed by Sopris Engineering in on June 10, 2021. The soils in the proposed field envelope area were sampled and characterized by application of the USDA visual/tactile soil texture method analysis from samples in a 7 foot deep profile pits and 5 foot deep excavations exposing the tank, effluent pipe and buried. distribution box. The shallow soils in these excavations were sampled, observed and tested at 2, 3 and 6 foot depths. The soils below nil to 4 inches of topsoil consist of medium dense sandy silt loam texture soil with slightly blocky to granular structure to a depth of 7 feet. The soil profile contains less than 20% scattered gravel or rock content to the 6-feet depth below the surface grades. The soils appear to be consistent across the site from observations in the excavations. No free water was encountered in the pit excavations. Seasonal high Groundwater levels are expected to be below 10 feet from the existing surface grades on the relatively flat terrain. The native soils sampled from 2-3 feet below the surface, in the vicinity of the proposed field, are characterized as a soil type 2 consisting of silt loam texture with granular structure. This soil has an effective loading rate for conventional soil treatment of 0.6 Gal/S.F./day for a level 1 conventional treatment system The equivalent percolation rate is assumed to be 20-30 minutes per inch. In order to provide optimal treatment in the limited available area, a pressure dosed STA utilizing enhanced manufactured media will be installed to provide for an enhanced treatment level TL-1 system. Intermittent Sand Filter Treatment Unit/ Absorotion System Design GeoMat-rm Treatment Unit/ Absorption System Design The treatment/absorption fields was designed based on utilizing the effective Long Term Acceptance Rate (LTAR) for pressure dosed GeoMat sand filter treatment beds with 6-inches of washed filter sand (ASTM-C33, "Concrete sand") below 4 rows of 39- inch wide GeoMat model 3900 manufactured treatment/distribution media, in accordance with Regulation 42 sections (43.10(C), 43.13.E.1.d, Table 10-2 and Table 10-3 as approved by CDPHE for this technology. Long Term Acceptance Rate (LTAR) Considering the allowable application of the OWTS regulation 43 and CDPHE approved proprietary Distribution Product for Geomatrix Systems, GeoMat product: Receiving septic tank effluent, the treatment level-1 for GeoMat requires a minimum 6" depth of filter sand media with the bottom of the sand layer defined as the infiltrative surface being at least 4-feet above a limiting layer (43.8, Table 7-2.4); Maximum hydraulic loading rate for TLl effluent is the long term acceptance rate of the receiving soil Type 2 is 0.6gal./S.F./day) (Table 10-1 & 10-1 A.). A(sf) = Qd x L.F.1 x L.F.2 .: A = Area; LTAR LTAR = 0.6 gaVS.F./day for silt loam Qd = flow (gal/day) for OWTS = 525 gpd L.F.1=1.0 pressure dosed bed application L.F.2=0.7 Enhanced Manufactured Media OWTS: A(sf) = 525 gpd x 1.0 x 0.7 = 612.5 S.F. 0.6 Gal/S.F./day The treatment field consist of two beds excavated 18" depth below finish grade installed with the specified length of GeoMat rows with the specified custom perforated distribution laterals and manufacturer supplied orifice shields below the specified OWTS As Constructed Certification 41 S. Pine, Carbondale SE Job No. 31132.01 November 24, 2021 Page 3 orifices on top of the GeoMat material. The distribution laterals were installed per manufacturers recommendations below the top geofabric cover. The completed geo mat beds were backfilled with suitable excavated materials to finish grade slightly mounded approximately 3 inches above the surrounding surface grades. The treatment field consist of two 24 feet long by 13 feet wide pressure dosed Geomat sand filter beds each with of 306+ square feet of absorption treatment area with (4) custom perforated pressure dose distribution laterals per bed. The 612.5 S.F. treatment field was installed with a total of 8 pressure dose distribution laterals equally pressured dosed by the high head pump assembly in the dosing basin, to a corrnnon 1.5" manifold pipe connected to each lateral running the width of the two beds . Each bed was constructed with 6-inches of washed filter sand below 4 rows of 39-inch wide GeoMat model 3900 manufactured treatment/distribution media. The dosing pump assembly was installed in the pump basin between the septic tank and the field to provide for equal pressure distribution of effluent across each treatment/absorption bed. The septic tank effluent is dosed through each individual 1.5" custom perforated pressure distribution lateral running the length of each bed centered on each 39" GeoMat material row. Effluent Distribution The dosing volume per cycle is 45 gallons that provides over 3 times the total pipe volume anticipating 6 dosing cycles per day. A ball valve were installed on the temunal end of each distribution lateral centered below and housed in an S" valve box with lid set 2" above surface grades. The minimum slope of the transport pipe from the dosing basin to the manifold was installed at a minimum 2.% upward slope to allow for drain back to the basin. A piezometer monitoring well pipe riser with caps were installed at the comers of the field and be extended down to the excavated surface depth at the bottom of the placed sand. OWTS Operation and Maintenance All components of the engineered OWTS shall be inspected on a regular basis and be properly maintained. The responsibility for repair and maintenance of the system will remain with the property Owner. The owner shall retain the services of qualified personnel to inspect the OW M and to perform all maintenance and repairs necessary to ensure that the system is in good operating condition and is in compliance with the manufacturer's performance requirements. The operating components of the OWTS shall be inspected by the engineer within 30 days of being placed into operation and thereafter every six months by the owner or qualified service provider. In general, for a properly utilized systern, septic tanks should be pumped every 3 - 5 years. The effluent filter should be cleaned every six months and at the time of pumping. Absorption fields should be maintained with suitable vegetative cover and kept free of root invasive plants. Positive surface drainage away from the absorption field should be maintained. If you have any question or need any additional information, please call. Sincerely, SOPRIS ENGINEERING, LLC Paul E. Rutledge Design Engineer V — �•'0 28377 ;24, 2021 Yancy Nichol, PE Principal