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HomeMy WebLinkAboutOWTS Design Revision 07.29.24 Onsite Wastewater Treatment System Design Revision July 29, 2024 Original: July 17, 2024 Port Everglades Restaurant Corp (P.E.R.C.) Project 4685 CR 346 Silt, CO 81652 Parcel No. 2179-181-00-123 Prepared By: K-Cronk Engineering, Inc. P.O. Box 140 Mack, CO 81525 970-250-0572 - 1 - Site History This report was originally prepared by the design engineer using information collected from neighboring properties as well as the USGS Web Soil Survey prior to a soils evaluation being done. A soils evaluation and site study were since conducted on the property of reference on 07/25/24 and the design has been modified to reflect actual site conditions. There is an existing three-bedroom residence on the site that is served by an existing onsite wastewater treatment system (OWTS) that is experiencing slow drainage and signs of failure. The owner of the property wishes to replace it with a new OWTS sized to accommodate three bedrooms total. The site consists of approximately 19 acres of cultivated native soil. Drainage is approximately 1% to the west. A soils evaluation and site study were conducted on the property of reference on 07/25/24 by Kachayla R. Cronka. The soils evaluation trench was located approximately 215’ south of the north property line and approximately 1,100’ east of the west property line. Development of Design Parameters The soils evaluation trench was extended to a depth of 96" below ground surface (BGS). No ground water was observed in the open excavation to a depth of 96" BGS. Evidence of periodically saturated soil was observed at a depth of 36" BGS. The limiting layer has been identified at this saturated depth of 36” BGS. The soils evaluation indicates two distinct soil horizons underlie the site. A lithological description follows: depth (in.) description 0” –78” clay loam, brown (Soil Type 3A, USDA –clay loam, massive, structureless) 78” – 96” clay loam w/ cobble; >35% rock (Soil Type R-1/3A, USDA – clay loam, massive, structureless) Based on the results from the 07/25/24 soils evaluation, Soil Type 3A and corresponding long term acceptance rate (LTAR) of 0.55 (TL3) are chosen for overall system sizing of a pressurized mounded soil treatment area (STA) designed to discharge to subsoils below the 36” depth is proposed for this project. a Kachayla R. Cronk holds a Certificate of Attendance and Examination from the CPOW Visual and Tactile Evaluation of Soils Training. - 2 - System Design A pressurized mound soil treatment area (STA) is proposed for discharge of septic effluent at the site. The STA will consist of one bed as shown in the included graphics. Construction of the system will consist of removing the native soils from the area underlying the bed of the proposed STA. The initial excavation will be continued to a level base at a depth of 36" BGS (see Soil Treatment Area Cross Section). Following completion of the initial push out, the open excavation will be backfilled with 36" (min. depth) of ASTM 33 concrete sand (secondary sand) to a surface elevation of 0” above ground surface. A gradation analysis done within 30 days of the installation date must be submitted to the design engineer and Garfield County to assure the sand conforms to secondary sand standards (Garfield County OWTS Regulations 43.11.C.d.3; effective size: 0.15-0.60 mm, uniformity coefficient: ≤ 7.0, percentage fines passing #200 sieve: ≤ 3.0). The sand used must be completely settled prior to installation of components as approved by the design engineer. Following installation of the mound, QUICK4 STANDARD INFILTRATORS (or equivalent) will be used to construct a septic effluent distribution system in the open excavation. The INFILTRATOR effluent distribution system will be installed in accordance with the "Infiltrator Technical Manual", available from Infiltrator Systems Inc., 123 Elm Street, Suite 12, Old Saybrook, Connecticut 06475. Adjacent INFILTRATORS shall be fastened with a minimum of three (3) ¾” self-tapping screws to prevent movement and separation during backfilling. After the INFILTRATORS are installed, synthetic filter fabric (140-200 mesh) will be placed over the INFILTRATORS and the system will be covered with a soil cap. The soil cap will consist of approximately 18” of sandy loam soil mounded 5% to promote surface run off away from the soil treatment area. The top of the cap will extend above the existing ground surface. Extension of the cap side slopes from the cap perimeter to the existing ground surface shall consist of: 1. Maintaining a slope no steeper than 3H:1V from the cap perimeter to the existing ground surface, and 2. Scarifying the native soil surface under the cap sidewalls to promote subsurface absorption. All required setbacks shall be taken from the edge of the sand bed. Septic effluent will be introduced into the soil treatment area through pressurized distribution laterals installed in each row of INFILTRATORS as shown in the included graphics. The injection laterals will consist of 1-¼” Schd 40 PVC pipe with 5/32" holes equally spaced 48" o.c. along each row of INFILTRATORS. Holes in the injection laterals will be drilled at 12:00 o’clock to direct effluent up for dispersal against the top of the chamber. Injection laterals shall be suspended from the top of the chamber with all-weather plastic pipe strapping (min. 120 lbs tensile strength) at every chamber joint connection. There is an existing, 1,000 gallon, two compartment septic tank on site that may continue to be used once it has been inspected and found to be in good working order. The existing tank is large enough to provide a minimum of 48 hours retention time for sewage generated from the proposed project. If the existing septic tank is not found to be in good working order, it must be abandoned in place or removed. Abandonment shall consist of pumping the tank of all solids prior to being crushed. All void space must then be filled with gravel, sand, or compacted soil. - 3 - A 300-gallon minimum, single compartment pump chamber will be placed down-gradient of the 1,000- gallon tank. A screened effluent pump will be placed in the pump chamber. The effluent pump system will employ an OSI high head, non-clog (3/4” solids handling capability), effluent pump (OSI model no. PF500511) and screened pumping vault (OSI model no. PVU57-1819-L). A 2" Schd 40 PVC pressure transport line will be used to transfer septic effluent from the pumping system to the STA. The pressure main will be self-draining or be buried a minimum of 36" below ground surface to prevent freezing. All pressure piping and construction shall be completed in accordance with the attached graphics. As shown in the attached graphics, the soil treatment area will consist of one bed 12’x69’ in lateral dimensions and encompass a total area of 828 sq. ft. DESIGN CALCULATIONS – UNLINED SAND FILTER DESIGN LOADING RATE OF 3 BEDROOMS @ 150 GAL./BEDROOM-DAY = 450 GAL./DAY ASSUMED DESIGN SOIL TYPE 3A LONG TERM ACCEPTANCE RATE (LTAR) OF RECEIVING SOIL (TL3) = 0.55 GAL./SQ.FT./DAY A = 𝑄 𝐿𝑇𝐴𝑄, WHERE, A = SOIL TREATMENT AREA (SQ. FT.) Q= DESIGN FLOW (GAL./DAY) LTAR = LONG TERM ACCEPTANCE RATE (GAL./SQ.FT./DAY) A = 450 0.55 =818.18 𝑆𝑄.𝐹𝑆. REQ’D: UNLINED SAND FILTER SIZED AT ONE BED 12’ x 69’ IN SIZE MINIMUM DESIGN CALCULATION – AREA OF DISTRIBUTION MEDIA LTAR OF UNLINED SECONDARY SAND FILTER = 0.80 GAL./DAY-SQ. FT. A = 450 0.80 =562.5 𝑆𝑄.𝐹𝑆. SOIL TREATMENT AREA ADJUSTMENT FACTOR FOR PRESSURE BED DESIGN = 1.0 SOIL TREATMENT AREA ADJUSTMENT FACTOR FOR USE OF CHAMBERS = 0.7 SOIL TREATMENT AREA = 1562.5 X 1.0 X 0.7 = 393.75 SQ. FT. REQ’D: 393.75 SQ.FT. / 12 SQ.FT. PER INFILTRATOR = 38 INFILTRATORS MINIMUM USE BED AREA OF 12’ x 69’ = 828 SQ. FT. INCREASE CHAMBERS TO 3 ROWS OF 15 QUICK4 STANDARD INFILTRATORS (or equivalent) FOR A TOTAL OF 45 UNITS - 4 - Installation - Setbacks, Notifications, and Inspections The owner and installer shall be aware of and comply with the following installation and system operation requirements. • The installer must be approved and licensed by Garfield County for installation of onsite wastewater treatment systems. • All installation activities shall be conducted in accordance with current Garfield County OWTS Regulations. If at any time during construction, subsurface site conditions are encountered which differ from the design parameters previously described, construction activities will stop, and the design engineer and Garfield County will be contacted to address any necessary design modifications. • The final cover shall not be placed on sewer lines, septic tank, or the soil treatment area until the system has been inspected and approved by the design engineer and Garfield County. The installer shall provide 48-hour notice for all required inspections. • Installation procedures including grade, location, setbacks, septic tank size, and soil treatment size shall conform with the attached graphic details. Construction activities and system components will not encroach upon existing easements or utility corridors. A minimum of 5 ft of undisturbed soil shall be maintained between individual absorption elements and the septic tank. A minimum of 4’ of undisturbed soil shall be maintained between adjacent absorption elements. • The installer must maintain all setbacks to utility lines, easements, property lines, or other adverse conditions, whether they are known and shown on the attached graphics or have been disclosed during construction. Vehicle traffic and parking is to be prevented over the soil treatment and repair area. Minimum setbacks for system components are: Septic Tank, Dosing Tank Building Sewer, Effluent Lines STA spring/well/cistern 50 50 100 potable water supply line 10 5 25 structure w/ crawlspace 5 0 20 structure w/o crawlspace 5 0 10 property lines, piped or lined irrigation 10 10 10 subsurface drain, intermittent irrigation 10 10 25 lake, water course, irrigation ditch, stream 50 50 50 cut slope steeper than 3H:1V 10 10 25 septic tank -- -- 5 • All gravity flow sewer lines and effluent distribution piping shall be 4 inches in diameter and have glued joints. All lines discharging sewage from the residence to the septic tank shall maintain a minimum fall of 1/8 in. per foot and shall employ sweep 90's or 2-45's at all turns. Sewer lines from the dwelling to the septic tank and at least 6 ft from the septic tank outlet must meet minimum standard ASTM-3034. Lines discharging from the septic tank to the soil treatment area shall maintain a minimum fall of 1/8 in. per foot. Sewer lines under driveways - 5 - shall meet the minimum Schedule 40 PVC standards. Additionally, effluent piping in traffic areas with less than 24" of cover shall be encased in 6" CMP or flow fill and covered with minimum 2" high density blue board insulation. • Sewer lines or domestic water lines shall be encased in minimum SCHD 40 with water -tight end caps or a minimum of 6” of flow fill at all points with less than 5’ separation between sewer and domestic water lines. • Four-inch clean outs shall be installed at maximum 100' intervals in all gravity flow effluent lines exceeding 100' in length. • A minimum of 12" of soil cover (18" recommended) shall be maintained over all gravity draining OWTS components to prevent freezing of septic effluent (excepting septic tank access ports which must be extended to the ground surface). • A minimum of 36” of soil cover shall be maintained over all non-draining pressure effluent line. • The septic effluent pumping system shall consist of OSI components (OSI, non-clog (3/4” solids handling capability) effluent pump model no. PF500511 and OSI screened pumping vault model no. PVU57-1819-L) as detailed in the attached effluent pumping system detail. The effluent pump control panel shall be Orenco model no. S1ETM. Electrical wiring shall be continuous cable with all connections made in a weatherproof box. Limit switching shall consist of: 1) low level/pump off, 2) high level/pump on, and 3) high level alarm/system failure. The high-level alarm shall be both audible and visual and shall be easily detectable by occupants. Emergency notification information (e.g., telephone numbers of owner, Garfield County, service personnel) shall be posted near the high-level alarm. • The effluent pump shall be configured with a minimum dose volume of 100 gal (16" float differential for single-compartment, 300 gal. tank). Storage capacity in excess of the high-level alarm shall be 6" above the pump-on float level. • All access manholes on septic tanks and dosing chambers will be child proof and contain appropriate warning labels if accessible to the public. Confined space entry precautions should be observed by maintenance personnel. • The system contractor shall be aware of the potential for construction activities to reduce soil permeabilities at the site through compaction, smearing, and shearing. The following precautions and construction procedures should be employed during installation to minimize disturbance to native soils: i. Excavation should proceed only when the moisture content of the soil is below the plastic limit. If a sample of soil forms a rope instead of crumbling when rolled between the hands it is too wet and should be allowed to dry before excavation continues. ii. Excavation and backfill equipment should work from the surface where at all practical to avoid compaction of the soils at depth. iii. The bottom and sidewalls of the excavation should be left with a rough, open surface. The appearance should be that of broken or ripped soil as opposed to a sheared, smeared, or troweled surface. Any smoothed or smeared surfaces should be removed with a toothed rake or shallow ripper taking care to remove loose residues from the bottom of the excavation by hand if necessary. iv. Care should be taken in placing fill materials in the excavation to avoid damaging the exposed soil surfaces. - 6 - Operation - Maintenance and Inspections • The owner shall install a structural barrier if necessary and take precautions to prevent vehicular traffic, excessive surface watering, accidental flooding, or other activities in the vicinity of the soil treatment area which may compact, saturate, or otherwise alter the subsurface soil parameters used in designing the septic system. • The owner will plant and maintain grass or other shallow rooted cover crop to prevent erosion and promote evapotranspiration over the soil treatment area. • The owner will inspect and maintain the required mounding and drainage away from the soil treatment area to prevent saturation from precipitation and surface flows. • To mitigate the generation of preferential flow channels which may compromise the operation of the system, the owner will inspect and prevent intrusion of burrowing animals and deep - rooted plants into the soil treatment area. • The septic effluent pump and the effluent pump filter shall be inspected and cleaned as necessary every six (6) months. • The owner will conduct periodic maintenance of the septic system by removing accumulated sludge from the septic tank every 3-4 years to prevent clogging of the soil treatment area. - 7 - Limitations This report is a site-specific design for installation of an onsite wastewater treatment system and is applicable only for the client for whom our work was performed. Use of this report under other circumstances is not an appropriate application of this document. This report is a product of K-Cronk Engineering, Inc. and is to be taken in its entirety. Excerpts from this report may be taken out of context and may not convey the true intent of the report. It is the owner's and owner's agent’s responsibility to read this report and become familiar with the recommendations and design guidelines contained herein. The recommendations and design guidelines outlined in this report are based on: 1) the proposed site development and plot plan as furnished to K-Cronk Engineering, Inc. by the client, and 2) the site conditions disclosed at the specific time of the site investigation of reference. K-Cronk Engineering, Inc. assumes no liability for the accuracy or completeness of information furnished by the client. Site conditions are subject to external environmental effects and may change over time. Use of this plan under different site conditions is inappropriate. If it becomes apparent that current site conditions vary from those anticipated, the design engineer and Garfield County should be contacted to develop any required design modifications. K-Cronk Engineering, Inc. is not responsible and accepts no liability for any variation in assumed design parameters. K-Cronk Engineering, Inc. represents this report has been prepared within the limits prescribed by the owner and in accordance with the current accepted practice of professional engineering in the area. No warranty or representation, either expressed or implied, is included or intended in this report or in any of our contracts. SEAL Kachayla R. Cronk, P.E. Date NOTE: This OWTS design is meant to include the following seven pages: 1) plot plan 2) septic layout plan 3) notes for your installer 4) soil treatment area plan view 5) soil treatment area cross section 6) pump vault detail 7) pump curve The plan is not to be implemented in the absence of these sheets. NOTES FOR YOUR INSTALLER • Please verify slope at the time of system installation – the orientation of the STA shown in this design has been determined based on existing site conditions at the time of the original site investigation, but that may have changed during construction and pre-construction grading of the site. • The depth of the trenches is determined by percolation rates and soil conditions relative to the existing ground surface at the time of the soils investigation. If the site slope or grading of the ground surface at the time of installation differs significantly from what was initially observed, the trench depths may have to be adjusted to make sure the infiltrative surface remains in the desired soil layer, and portions of the trenches don’t end up too deep or too shallow. The depth of the soil cap relative to finished grading is not part of the OWTS design criteria. • Please provide K-Cronk Engineering with a copy of the septic tank manufacturer’s specification sheet verifying maximum backfill depth. Tanks must be backfilled according to manufacturer’s specification. Pressurized System Notes • Please provide K-Cronk Engineering a copy of the sand sieve analysis, if relevant, dated within 30 DAYS of installation before purchasing/installing the sand so we can check that it meets Garfield County OWTS standards. • Pump floats do not come pre-set from the factory. Please refer to the Pump Vault Detail for the distance needed between the on/off floats. Please reach out at any time during the installation process if you have any questions! ____________________________ Kachayla Cronk – (970) 250-0572 Effluent Pumping System for Cold Weather Applications (cw style) Orenco Systems Incorporated Pump Selection for a Pressurized System - Single Family Residence Project PERC 4685 CR 346 Parameters Discharge Assembly Size Transport Length Transport Pipe Class Transport Line Size Distributing Valve Model Max Elevation Lift Manifold Length Manifold Pipe Class Manifold Pipe Size Number of Laterals per Cell Lateral Length Lateral Pipe Class Lateral Pipe Size Orifice Size Orifice Spacing Residual Head Flow Meter 'Add-on' Friction Losses 2.00 100 40 2.00 None 15 6 40 2.00 4 46 40 1.25 5/32 4 8 None 0 inches feet inches feet feet inches feet inches inches feet feet inches feet Calculations Minimum Flow Rate per Orifice Number of Orifices per Zone Total Flow Rate per Zone Number of Laterals per Zone % Flow Differential 1st/Last Orifice Transport Velocity 0.86 48 41.2 4 1.4 3.9 gpm gpm % fps Frictional Head Losses Loss through Discharge Loss in Transport Loss through Valve Loss in Manifold Loss in Laterals Loss through Flowmeter 'Add-on' Friction Losses 3.4 2.8 0.0 0.0 0.3 0.0 0.0 feet feet feet feet feet feet feet Pipe Volumes Vol of Transport Line Vol of Manifold Vol of Laterals per Zone Total Volume 17.4 1.0 14.3 32.8 gals gals gals gals Minimum Pump Requirements Design Flow Rate Total Dynamic Head 41.2 29.5 gpm feet 0 1020304050607080 0 20 40 60 80 100 120 140 160 Net Discharge (gpm) PumpData PF5005 High Head Effluent Pump 50 GPM, 1/2HP 115/230V 1Ø 60Hz, 200/230V 3Ø 60Hz Legend System Curve: Pump Curve: Pump Optimal Range: Operating Point: Design Point: