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HomeMy WebLinkAboutOWTS ReportGARFIELD COUNTY OWTS REPORT LOT 27, LOOKOUT MTN. RANCH GLENWOOD SPRINGS, COLORADO October 2021 Prepared by 118 West Sixth Street, Suite 200 Glenwood Springs, CO 81601 970.945.1004 970.945.5948 fax 2 GARFIELD COUNTY OWTS REPORT LOT 27, LOOKOUT MTN. RANCH GLENWOOD SPRINGS, COLORADO “I hereby affirm that this Onsite Wastewater Treatment System (OWTS) report for Lot 27, Lookout Mountain Ranch, Glenwood Springs, Colorado was prepared by me, or under my direct supervision, for the Owners thereof in accordance with the provisions of Garfield County’s OWTS Regulations and approved variances and exceptions listed thereto. I understand the County does not and will not assume liability for OWTS facilities designed by others.” ______________________________________ License No. ____________________ Licensed Professional Engineer, State of Colorado (Affix Seal) PREPARED BY: TERRY BENDETTI, P.E. SGM Project # 2021-644-001 10/18/2021 3 TABLE OF CONTENTS 1.0 Introduction 5 2.0 Preliminary Investigation 5 3.0 Recommendations 5 4.0 Installation Observations 7 5.0 Operation and Preventative Maintenance Schedule 7 6.0 Limitations 8 4 Appendix CBO, Inc. Subsurface Investigation Drawing Sht 1 Drawing Sht 2 Drawing Sht 3 OWTS Design Spreadsheet 5 1.0 Introduction This report presents the design of an Onsite Wastewater Treatment System (OWTS) for Lot 27 of the Lookout Mountain Ranch Subdivision. Minimum setbacks required in Table 7-1, Section 43.7 of Garfield County’s Regulation 43 are met. There is no floodplain mapping by FEMA for this property. SGM personnel contributing to this report are: · Terry Bendetti - PE/CPOW Certified Competent Technician/NAWT Certified Designer 2.0 Preliminary Investigation The subsurface investigation was conducted by CBO, Inc. and presented in their report dated September 11, 2021, Project Number C1561. CBO, Inc. report is included in the Appendix. 3.0 Recommendations An OWTS as a wastewater treatment system is suitable for this site. At a minimum, the OWTS shall have: · A septic tank. · Trench type soil treatment areas (STA). · Category 3 distribution media in the STAs. · A distribution box. · 4” diameter perforated distribution laterals. · 4” diameter solid wall influent and effluent lines. Untreated wastewater from the residence will be conveyed through influent lines, by gravity, to a new septic tank. Treatment level 1 (TL-1) will be provided by the septic tank and effluent from the tank will be conveyed through effluent lines to a distribution box. The distribution box will divide the effluent flow into equal volumes to be delivered to each distribution lateral and discharged onto the infiltrative surface. All effluent flow will be by gravity and influent/effluent lines shall be installed per associated plans and details. The proposed residence is a 3-bedroom, single family residence. Per Table 6-1 of the County’s Regulation 43 the design flow rate will be 450 gpd (gallons per day). # Bedrooms Occupancy (# of Persons) Wastewater Flow per Person Design Flow (gpd) 3 6 75 450 The OWTS STA site elevation is approximately 8,406 feet above sea level (NAVD 88) and it will be located south of the proposed residence. The septic tank will be installed south of the driveway slab. Both locations are shown on sheet 1. Sewer Pipe: Sewer influent and effluent pipe shall be 4-inch solid wall SDR-35 PVC installed per the associated plans, adjustments in the field are allowed as field conditions warrant. If adjustments are made, a minimum grade of 2% and a maximum grade of 15% must be maintained. If the maximum grade of 15% cannot be maintained installation of a stepdown will be required. Joints shall be solvent welded. Cleanouts are required: 6 1) Within 5 feet of the existing building. 2) At spacing not to exceed 100 feet. 3) Upslope of two or more bends closer than 10 feet. All 90 degree bends shall be constructed using two, 45 degree fittings. The pipe shall be properly bedded per the typical trench detail presented on sheet 3. There must be a minimum cover of 42-inches over influent and effluent piping. If this requirement cannot be achieved, insulation must be installed over the pipe. If insulation over the piping is required, it must be installed per the detail on sheet 3 and continue over the piping until the minimum cover of 42-inches can be met. Septic Tanks: One new 1,000 gallon septic tank with two bays will be required. The tank must be on the Colorado Department of Public Health and Environment’s accepted septic tank list. The tanks and lids shall conform to current County OWTS regulations, section 43.9.A and 43.9.B, in addition to being traffic rated. The tanks shall be installed with insulated, watertight access risers having lids that can be secured. Risers shall meet the tank manufacturer’s requirements for type and installation. There shall be an effluent filter and its handle shall extend to within twelve inches of the lid. The septic tank shall: 1) Be located down gradient of the home. 2) Have a covering of no more than 4.0-feet in depth, measured from the top of the tank lid to finished grade surface. 3) Be at a location accessible for pumping and maintenance. Prior to installation of the tank, the installer must ensure tank placement as shown on the plans will allow connection of the tank’s inlet invert to the influent piping from the residence. If tank installation can’t be accomplished as shown on the plans, the tank can be set to have between 1.0 to 4.0-feet of cover over its lid, measured from the top of the lid to surface grade. If cover thickness is less than the minimum 1.0-foot, or more than the maximum 4.0-feet, the tank can be moved closer or farther from the residence to meet cover thickness requirements. A septic tank having a cover thickness less than 1.0-foot or greater than 4.0- feet will not be allowed. Influent and effluent pipe alignments can be adjusted if movement of the tank is required by following sewer pipe requirements above. Distribution Box: The distribution box shall be set as shown on sheets 1 and 2, in a manner to distribute effluent equally to the distribution laterals of each trench. The Engineer should be contacted if alignments or locations change in order to verify regulation requirements are maintained. The box should be capable of one inlet pipe having an insertion point a minimum of 1-inch above outlet openings and 3 outlet openings. Boxes with more than 3 outlet openings will have the excess openings plugged. Soil Treatment Area: The soil treatment area was sized using criteria found in section 43.10 of the County’s Regulation 43 for a 3-bedroom residential home using: · Trenches for the soil treatment area. · Effluent application by gravity. · Chambers for the distribution media. The following table summarizes sizing of the STA. 7 No. Bedrooms Daily Design Flow (gpd) LTAR Method of Application Adjustment Factor Distribution Media Adjustment Factor STA Size (sf) No. Chambers (12sf/chamber) 3 450 0.60 1.0 0.7 525 44 The STA shall be excavated as field conditions require using the following guidelines. 1. Three trenches having a total of 44 infiltrators. Two trenches with15 infiltrators, one trench with 14 infiltrators. 2. Trench widths shall be 3-feet. 3. Trench lengths shall be 60-feet. 4. A minimum of 4-feet, measured sidewall to sidewall, shall separate trenches. 5. The infiltrative surface shall be no greater than 4-feet from the surface. 6. Trench floors shall be level and set at the infiltrative surface elevation shown on section A-A’, sheet 2. 7. Chambers shall be placed per the manufacturer’s directions. Chambers shall have a minimum of 10.8 square footage of bottom area per the County’s Regulation 43 requirement, section 43.13. An impervious liner per sheets 1 and 2 shall be installed adjacent to the most downslope trench to prevent potential lateral movement of effluent from surfacing. The STA shall have a final soil cover as described on sheet 3. This may mean that the STA cover will need to be 16-inches +/- when initially placed to allow for settlement over the freeze-thaw of a winter season. The surface of the STA shall be seeded after installation of the system. A native, upland seed mix should be used. These mixes do not require irrigation and develop a growth 10 to 15 inches high. No automatic sprinkler system shall be installed over the STA. Vehicular traffic and livestock shall be kept off of the STA. No landscaping, impervious surfaces or plastic sheeting can be installed over the STA, which will reduce performance of the STA. 4.0 Installation Observations Installation of the OWTS tank, influent/effluent lines, distribution box and infiltrators shall be observed by the design engineer. Our office shall be notified by calling 970-945-1004 at least three days in advance to schedule personnel to observe installation of these features. Installation of these features should be substantially complete and ready to be backfilled prior to requesting individual or simultaneous observation for these features. 5.0 Operation and Preventative Maintenance Schedule The goal of an operation and maintenance schedule is to observe the operation, and perform minor maintenance to the onsite wastewater treatment system to allow for proper long-term functioning of the system. Septic tanks: The scum and sludge accumulation in the septic tanks shall be monitored yearly. Once the cumulative scum or sludge thickness reaches 25% of the tank depth, the entire tank shall be pumped. A pumping frequency of 1 to 3 years is expected at design flows. An alternative is a regular pumping frequency of every 2 years. 8 Effluent Filter: The effluent filter at the septic tank discharge shall be cleaned (hosed off) at the time of pumping or as needed. General: System users must realize that an on-site wastewater treatment system is different from public sewer service. There are daily considerations, such as not putting plastic or other non- biodegradable material into the system. Water use shall be monitored so that toilets are not allowed to leak when seals malfunction. Allowing fixtures to flow continuously to prevent water lines from freezing is not acceptable. Although the proposed system can accommodate variable flows, spreading water use over several hours and eliminating peak flows is recommended. To illustrate the point, a malfunctioning toilet can discharge in excess of 1,000 GPD. Excessive daily loading could flood and irreparably harm the STA. SGM recommends against installation of a water softener. The chemical and hydraulic loading from the backwash of a water softener would be damaging to the STA, so if a softener is installed a separate drywell shall be constructed for the backwash waste. No landscaping or plastic can be used over the STA, which would reduce the performance of the STA. Design of the OWTS is based on treatment of domestic sewage only. Swimming pool or spa water is not to be discharged into the OWTS. The proposed OWTS design is based on the regulatory flows noted in the attached calculations. Increased flows may hydraulically or organically overload the OWTS, causing premature failure. 6.0 Limitations Our investigation, layout, design, and recommendations are based on site visits and the best information available at the time. The contents of this letter shall not serve as the basis for any third party engineering design. If conditions that are considerably different from those described in this report are encountered, SGM shall be called to evaluate the conditions. If the proposed construction is changed, SGM shall be notified to evaluate the effect of the changes on the OWTS prior to the changes being made. All construction shall be in accordance with the Garfield County OWTS Regulations. Pipe type and size, burial requirements, septic tank construction, and other specifications, which are not depicted in our report, shall conform to the requirements of the County’s OWTS Regulations. The installer of the system shall be acceptable by the County’s Environmental Health Department. 9 Appendix CBO, Inc. Subsurface Investigation Drawing Sht 1 Drawing Sht 2 Drawing Sht 3 OWTS Design Spreadsheet CBO, Inc. Subsurface Investigation 129 Cains Lane Carbondale, CO 81623 970.309.5259 carla.ostberg@gmail.com September 11, 2021 Project No. C1561 Russell Schweiss sunny6398@yahoo.com Subsurface Investigation Lot 27, Lookout Mountain Ranch Garfield County, Colorado Russ, CBO Inc. performed a subsurface investigation to determine sizing for an onsite wastewater treatment system (OWTS) design. The 35.65-acre property is located outside of Glenwood Springs, in an area where OWTSs and wells are necessary. Legal Description: Section: 18 Township: 6 Range: 88 Subdivision: LOOKOUT MTN. RANCHES RANCH 27 THIRD AMENDED RANCHES 23 & 25 - 27 & 33 Parcel ID: 2187-181-02-027 SITE CONDITIONS The property is currently developed with a small cabin with no plumbing. A new, 3-bedroom single-family residence is proposed. The residence will be served potable water from a well and cistern. Both the well and cistern must be at least 50-feet from the proposed septic tank and at least 100-feet from the proposed soil treatment area (ST). A water line runs along the southwest side of the driveway. The water line must be at least 10-feet from the proposed septic tank and at least 25-feet from the proposed STA. The proposed soil treatment area (STA) will be located to the southwest of the proposed residence. The area is vegetated with native grasses, sage, and scrub oak. There should be no traffic or staging of material over the future STA site to avoid compaction of soils prior to construction of the STA. SUBSURFACE The subsurface was investigated on October 1, 2020 by digging two soil profile test pit excavations (Test Pits). A visual and tactile soil analysis was completed by Carla Ostberg at the time of excavation.1 The materials encountered in the Test Pit #1 consisted of medium brown loam to 6.0-feet, underlain medium brown loam with lava rock to a maximum depth explored of 7.0-feet. No bedrock or groundwater was encountered. 1 Carla Ostberg holds a Certificate of Attendance and Examination from the CPOW Visual and Tactile Evaluation of Soils Training. Page 2 The materials encountered in the Test Pit #2 were similar to those encountered in Test Pit #1 with difficult digging beyond 6.0-feet. No bedrock or groundwater was encountered. A sample of the soils was taken from Test Pit #1 at 3-feet below grade. Soil structure grade was moderate. The soil formed a ball and a ribbon approximately 1-inch in length before breaking. Soil structure shape was blocky and consistence was friable. Soil texture was both gritty and smooth. We recommend STA sizing based on Soil Type 2, Loam with moderate structure grade. A long term acceptance rate (LTAR) of 0.6 gallons per square foot is recommend. We recommend a shallow installation of the infiltrative area, at approximately 2-feet below grade. Test Pit #1 Page 3 Backfill Sidewall moderate structure grade Sieved sample Ribbon less than 1-inch in length before breaking Page 4 Lava rock at the bottom of Test Pit #1 Test Pit #2 backfill Test Pit #2 sidewall moderate, difficult digging below 6-feet Page 5 LIMITS: This report is based on information submitted and observations at the time of our site visit. If soil conditions encountered are different from conditions described in report, CBO Inc. and the design engineer should be notified. All OWTS construction must be according to the county regulations. Requirements not specified in this report must follow applicable county regulations. The contractor should have documented and demonstrated knowledge of the requirements and regulations of the county in which they are working. Licensing of Systems Contractors may be required by county regulation. Please call with questions. Sincerely, CBO Inc. Carla Ostberg, MPH, REHS DECIDUOUS 4" X 9' ELE: 8413.6' GARAGECABIN G R A V E L R O A D ASPEN CLUSTERS PINE X 2 18" X 14' ELE: 8408.3' ASPEN 10" X 20' ELE: 8406.7' ASPEN 9" X 12' ELE: 8406.0' ASPEN 9" X 12' ELE: 8404.4' ASPEN 9" X 12' ELE: 8404.9' PINE 16" X 18' ELE: 8400.6' PINE 14" X 15' ELE: 8399.2' PINE 14" X 18' ELE: 8396.9' PINE 18" X 20' ELE: 8398.3' PINE 10" X 15' ELE: 8397.4' PINE 10" X 18' ELE: 8395.9' PINE 10" X 14' ELE: 8392.6' PINE 10" X 18' ELE: 8395.1' PINE 10" X 18' ELE: 8392.6' CONIFEROUS 12" X 12' ELE: 8389.8' PINE 10" X 15' ELE: 8388.7' PINE 14" X 14' ELE: 8383.8' 40.00 60.00 60' GOOSEBERRY PARK ROAD PER PLAT REC. 535970 END GOOSEBERRY PARK ROAD 40' ACCESS EASEMENT FOR RANCH 33 & 60' EASEMENT FOR WATER WELLS, PIPELINES STORAGE &^ RELATED FACILITIES PER PLAT REC. 535970 BOULDER LINED DRIVEWAYSUNLIGHT PEAKCHAIR MTN.SOPRISCAPITOL PEAK INDE PEND ENCE PA S SDYHYARD HYD. E ELEC. PANEL 19.9' 3 0 . 9 '19.9'3 0 . 9 '12.3'2 0 . 0 '12.3'20.0'8435843084258420 8415841084058400 8395 8390 838583808400 8405 8410 8415 84208425 84218432=100'-0"8431.58427.2 8424.7 28431.5105'-0"=84378436.58431.588'-10 5 8 " = 8420.8 9 0102030405062021190713121415222308091011161718102'-6"=8434.58434.5SCRUB OAK CLUSTER SCRUB OAK CLUSTER 10 RI S E R S @ 7 7 16"7 RI S E R S @ 7 3/ 8"8431.5R5 9 . 7 4 'R72.51' 8420.4 7 8420.4 7 8420. 47 8420. 89 8420. 8 9 8420. 8 9 8420. 89 8420. 8 9 8430 8434 8435. 2 8 84408436 84308439.5'8439.5'8438'8438'8435.28'8435.28'8433.28'8433.28'8431.28'8431.28'8427.28'8430.28'8430.28'8427.28'8425.28'YEA-LIH YEN RESIDENCERANCH 27, LOOKOUT MTN. RANCHGLENWOOD SPRINGS, COA1.0 ERIC REWINKEL 970-319-8534 ericr@esopris.com 5/15/21 - DESIGN DEVELOPMENT SITE PLAN SCALE 1" = 20' - 0" 1 00 SF 6/13/21 - PROGRESS - CD #1 8/31/21 - PROGRESS - CD #1 A1.0, 8/31/2021 7:16:00 AM APPROX LOCATION OF TEST PIT #2 APPROX. LOCATION OF TEST PIT #1 Garfield County, CO Developed by Account Number R030034 Par cel Number 218718102027 Acr es 36 Land SqFt 0 T ax Ar ea 005 2019 Mill Levy 62.7420 Physical Addr ess 0 GL ENWOOD SPRINGS 81601 O w ner Addr ess YEN, YEA L IH 3901 MO UNTAIN DRIVE #10 GL ENWOOD SPRINGS C O 81601 2019 Total Actual Value $145,840 Last 2 Sa les Date Pr ice 7/21/2020 $0 7/21/2020 $325,000 Date created: 9/11/2021 Last Data Uploa ded: 9/11/2021 2:05:29 AM 921 ft Overvi ew Legend Parcels Roa ds Parcel/Account Number s Highw ays Limited Access Highwa y Major Road Loca l Roa d Minor Road Other Road Ra mp Ferry Pedestria n Way Owner Na me Lakes & River s County Boundar y Line Drawings 1 9 . 9 '30.9'1 9 . 9 '30.9'12.3'20.0'12.3'20.0'R59.74'R72.51'Graphic ScaleIn Feet: 1" = 20'0102040Title:OWTS PlanRevision#Dwg No.Yea-Lih Yen Residence Ranch 27, Lookout Mtn. Ranch Glenwood Springs, COJob No.Drawn by:Date:File:PE:QC:2021-644.001TLB10/18/2021TLBOWTS-SitePlanXX118 West Sixth Street, Suite 200 Glenwood Springs, CO 81601 970.945.1004 www.sgm-inc.com Date By:1 3Of :For PermitProject Milestone:10/18/2021 Graphic ScaleIn Feet: 1" = ###'0#########Title:Effluent Line Profile andTrench Section A-A'Revision#Dwg No.Yea-Lih Yen Residence Ranch 27, Lookout Mtn. Ranch Glenwood Springs, COJob No.Drawn by:Date:File:PE:QC:2021-644.001TLB10/18/2021TLBOWTS-SitePlanXX118 West Sixth Street, Suite 200 Glenwood Springs, CO 81601 970.945.1004 www.sgm-inc.com Date By:2 3Of :For PermitProject Milestone:·····10/18/2021 ···········Graphic ScaleIn Feet: 1" = ##'0######Title:OWTS DetailsRevision#Dwg No.Yea-Lih Yen Residence Ranch 27, Lookout Mtn. Ranch Glenwood Springs, COJob No.Drawn by:Date:File:PE:QC:2021-644.001TLB10/18/2021TLBOWTS-SitePlanXX118 West Sixth Street, Suite 200 Glenwood Springs, CO 81601 970.945.1004 www.sgm-inc.com Date By:3 3Of :For PermitProject Milestone:QUICK4 STANDARD MULTIPORT END CAPINFILTRATOR SYSTEMS INC.QUICK4 STANDARD CHAMBERINSPECTION PORT(EFFECTIVE)34"12"10/18/2021 OWTS Design Spreadsheet Lot 27 Lookout Mountain Ranch Design Flow (GPD) # Bedrooms 3 450 Auxilliary Bldngs Bath/Shower N/A 0 Dishwasher N/A 0 Kitchen Sink w/Garbage Grinder N/A 0 Laundry Washer N/A 0 Lavatory N/A 0 Water Closet (toilet)N/A 0 Total Design Flows 450 gpd SITE CRITERIA Soil Type LTAR 1 2 X 0.6 2A 3 3A 4 4A 5 Soil Loading Rate =0.60 Based on Table 10.1 Soil Treatment Area = STA = Design Flow/LTAR 750 ft2 Size Adjustment Factors for Method of Application in STA Type of Absorption Area Method of Effluent Applcation Gravity Dosed (siphon or pump) Pressure Dosed Trench x Bed Size Adjustment Factors for Types of Distribution Media in STA Category 1 - Rock or Tire Chips Category 2 - Other MFG Media Category 3 - Chambers or Enhanced Media Type of Distribution Media X Size Adjustment for Method of Application = 1 Size Adjustment for Type of Distribution = 0.7 Adjusted STA Size = 525 ft2 Number of Infiltrators =44 Number Trenches 3 Number Infiltrators/Trench (2) Trenches @ 15 Infiltrator (1) Trench @ 14 Infiltrator Septic Tank Size = 1000 gallons