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HomeMy WebLinkAboutOWTS Design   www.sgm-inc.com  September 24, 2019    Mr. Andy Schwaller, Building Official  Garfield County Building Department  108 8th Street  Glenwood Springs, CO  81601    RE:    Cody OWTS    Section:20 Township:6 Range: 89 TR of Land in SW Cont      Glenwood Springs, CO  81601    Dear Andy,    The purpose of this letter is to provide you soils and design information relative to a tactile soils analysis that  SGM has performed on behalf of Paul Cody in support of installing a new OWTS at his proposed residence at the  above location.  The site sits east of S Marsh Lane above Three Mile Creek on a 32.32‐acre parcel in Section:20  Township:6 Range: 89 TR of Land in SW Cont.  The proposed OWTS will serve a 3‐bedroom single family  residence with the potential for expansion to handle capacity for a second residence on the property totaling 7  bedrooms.  The following figure identifies the location of the property from the County’s GIS website.        Figure 1 ‐ Site Location  From the NRCS Websoil Survey, the on‐site soils (for the STA) are identified as a Cochetopa‐Jerry complex.  A  soils study was performed by Kumar & Associates on August 2, 2019. The findings from the soils study generally    www.sgm-inc.com  agrees with the Websoil Survey. We have attached a soil report from the NRCS Websoil Survey to describe  further the expected characteristics of the soils determined through the pre‐site investigation.  Our preliminary  findings of the soil concur with those characteristics identified by NRCS in their soil investigation for the Websoil  information.  Specifically, findings for the site are as follows:    1.  Groundwater was not encountered at the time the test pits were dug.  2.   Depth to limiting layer (ie., ground water or bedrock) is greater than 8 feet.   3.  The sample contained less than 35% rock, >2mm.  4.  Two test pits have shown that other than a limited depth of topsoil, the soil horizon(s) below the topsoil  consists of very gravelly sandy loam or clay.   5.   Differing soil textures prompted an analysis of percolation rates to determine the soil type. An average  of the percolation rates for all three percolation tests indicate a Soil Type 3 in Table 10‐1 of Regulation  43 from CDPHE.    Based upon our understanding of the project and the above parameters, a standard OWTS design is sufficient  containing a 1,250 gallon tank for each home, a single pump vault and a single STA utilizing a pressurized dosing  system.  Therefore, this design can suffice for the future added home as long as these parameters are adhered  to.     The system is sized for 7 bedrooms with a soils percolation rate averaged at 51.3 minutes per inch.  As noted,  this is a proposed design with the potential for a second residence and septic tank to be added at a later time.  Calculations have shown that two trenches will be required for the initial three‐bedroom residence with three  additional trenches shown for the future four‐bedroom residence (indicated as Alternate 1 in the calculations).   It is recommended, and the plan shows to install 5 trenches now, utilizing 3 (which is slightly oversized for the  first home, indicated as Alternate 2 in the calculations), then connect the last two trenches from the ADV to the  full field.  It will be determined by the owner to install the additional trenches now or when the second  residence is built. Soil condition and type will be confirmed again at time of installation.     Pressure Dosed Trench System    As you will see on the schematic drawings for this design and the information attached, the homes will each need  to utilize a proposed 1,250 gallon septic tank. From the septic tank, the effluent would then flow by gravity to the  pump and dosing box and then to the distribution box for the Soil Treatment Area (STA) which is proposed to be  Infiltrator Quick4 chambers constructed in a trench format.  A variety of bends and clean outs would need to be  installed from the tanks to the distribution box.   Should the trenches for the future residence be installed, only  two of the ports for the automatic distribution valve will be connected, while the three future trenches will have  their ports closed until such time as they are needed with the four additional bedrooms. Each of the chambered  trenches are to be installed at a constant level (ie., 24” to 48” below grade) as equal flow distribution is being  accomplished through the pressurized system.  Trench lengths are indicated on the plans as associated with the  two homes.      www.sgm-inc.com    Standard end caps are proposed on the end of each trench along with inspection ports.   The piping from the tank,  distribution box and infiltrator trenches shall be a minimum diameter of 1‐1/2” diameter ASTM 3034 PVC, with  field flow testing of the pump to establish the number of 1/8” holes needed for 3‐5’ of spray head and maximize  the potential for even distribution in the field and ensure the flush valve at the end of each trench is installed to  appropriate height. The location of the tank, distribution box, gravity pipe route and infiltrator trenches are  approximated in the attached drawing plan of this package.  It is likely that each trench will be at a different  elevation requiring the field spray test for each.   Note that the drawing package is prepared in a schematic format  that relies on the contractor provide adequate grading to accomplish the intent of the design.  In this manner, it  is anticipated that field modifications will be necessary but not alter the resultant performance design.       The component construction for the system will need to follow the requirements of Sections 43.8, 43.9 and 43.10  of regulation 43 (as adopted by Garfield County) for the tank, pressure system, piping and STA as applicable.  We  have attached a copy of each of these sections for reference by the contractor to assure each component  construction is adequately addressed.    Upon your receipt and review, if you have any questions, please don’t hesitate to call.    Respectfully,  SGM        Rick L Barth, PE  Senior Engineer  Jordan Kehoe, EI  NAWT #14027DES    Attachments:   OWTS plan drawing   Calculation sheets for OWTS design   Preliminary Pump recommendation   Orenco ADV cutsheet   HP/Kumar select pages from geotechnical investigation   Garfield County Reg 43 select sections    Client:Jack Cody Project Location:Section 20 Lot 32, Mountain Springs Ranch Township 6S GWS, CO 81601 Range 89W Date: 13‐Sep‐19 Flow Data for the OWTS Design:: Current Application STEP # Bedr flow per BR 1 Home Use BR count 3 150 450 Add'l Bedrooms 075 0 Total= 450 gpd Home Use 450 gpd 1.2 #/day Totals:450 gpd 1.2 #/day Flow Data for the OWTS Design:: FUTURE HOUSE # Bedr flow per BR 1 Home Use BR count 3 150 450 Add'l Bedrooms 175 75 Total= 525 gpd Home Use 525 gpd 1.6 #/day Totals:525 gpd 1.6 #/day Total, All contribution 975 gpd 2.8 #/day Desigining one STA for all contributing flows OWTS Design Report and Calculations Home use, 2 pp BR for first 3 BR, then 1 per above 3 BR Home use, 2 pp BR for first 3 BR, then 1 per above 3 BR Soil Data for the OWTS 2 Data from on‐site soil observations (Data from HP Kumar): Appears to be a gravelly sandy loam, dense at depths of 3' ‐ 6' and below. At a depth of 8', neither bedrock or groundwater have been encountered. Web Soil Survey Classification(s): Cochetopa‐Jerry complex stony loam / cobbly clay loam / cobbly clay Web Soil Survey Classification(s): Cochetopa‐Jerry complex Field Soils PP1 PP2 (gravel removed) Gravels 57 9 Clay 3 7% 51 56% Silt 10 23% 22 24% Sand 30 70% 18 20% PERC 1 80 PERC 2 30 PERC 3 44 Average of 3 percolation holes: 51.3 mpi Soil classification provided by HP Given the consideration of all data, the Long Term Acceptance Rate to use is 0.35 gallons/sf/day (soil type 3) Septic Tank Sizing Current Application 3 Flow calculated from above: 450 gpd 48 hour detention time for septic tank sizing; Volume=  900 gpd Future House Flow calculated from above: 525 gpd 48 hour detention time for septic tank sizing; Volume=  1050 gpd Install 1250 gallon tank FOR EACH HOUSE, affirms GC Code section 43.9.B.2 Dosing Tank Sizing Typically max of ADF/4 ‐‐  minimum of pipe volume X 4 + dist pipe volume 4 Flow calculated from above: 450 gpd Current Application Dose rate is ADF/4:112.5 gp dose Go with  250   gallon dosing tank Future House Flow calculated from above: 975 gpd Dose rate is ADF/4:243.75 gp dose, max Go with  250   gallon dosing tank Compare with Pipe Volume, single trench dose at a time One trench pipe volume, complete:11.4 gal 1.5" pipe Minimum dose (4 x above, + dist vol)51.1 gp dose, min Avg 56 LF Start with: 102.2 gp dose   In full buildout, would equat to:9.5 doses per day **This allows us to be under recommended maximum for 3 BR, but then within range  of full buildout BR count Sizing of Absorption Field or Soil Treatment Area 5 Going with a soil type 3 and Treatment Level 1, LTAR = 0.35 g/d/sf For a pressure dosed system, size adjustment factor is 1.0 for a bed configuration For a gravity system, the size adjustment factor shall be 1.2 for a bed configuration For a gravity trench system, adjustment factor = 1.0 For a siphon or pump dosed system, adjustment factor= 0.9 For a pressure dosed trench system, adjustment factor = 0.8 For use of chambers:  size adustment factor is 0.7 STA= Flow/LTAR 2786 square feet (unfactored) 1286 Current Application 1500 Future House T.A. FUT For a chamber system, adjust size to 0.7 = 900 1050 square feet Incorporating a pressure dosed trench system, adjust size to 0.8=720 840 square feet Incorporating a siphon or pump dosed system adjust size to 0.9=NA NA square feet Utilizing a 36" wide chamber for the above selected system.3 3 feet Therefore:: Current Application For a pressure dosed chamber system in a trench configuration, length=240 280 feet total length of chambers Number of trenches selected (max 150' length)23# of trenches Length of trenches 120 93 feet each trench Therefore:: Construct 5 trenches now, 2 at 120 LF, 3 at 96 lf (utilizing the Quick 4) Alternate 1: Construct 2 trenches, 120 LF long for this application Construct 3 trenches, 96 feet long for future house Alternate 2: Construct all 5 trenches at 104 feet long.  Utilize 3 now for dosing, then all 5 at full build Alternate 3: NONE Pump Selection for a Pressurized System - Multiple Family Residence Project Cody OWTS / Garfield County Parameters Discharge Assembly Size Transport Length Before Valve Transport Pipe Class Transport Line Size Distributing Valve Model Transport Length After Valve Transport Pipe Class Transport Pipe Size 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 1.50 60 40 1.50 6605 80 40 1.50 5 20 40 1.50 5 120 40 1.50 1/8 4 3 None 0 inches feet 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 Before Valve Transport Velocity After Valve 0.34 31 10.5 1 5.0 1.7 1.7 gpm gpm % fps fps Frictional Head Losses Loss through Discharge Loss in Transport Before Valve Loss through Valve Loss in Transport after Valve Loss in Manifold Loss in Laterals Loss through Flowmeter 'Add-on' Friction Losses 0.3 0.5 4.1 0.6 0.0 0.3 0.0 0.0 feet feet feet feet feet feet feet feet Pipe Volumes Vol of Transport Line Before Valve Vol of Transport Line After Valve Vol of Manifold Vol of Laterals per Zone Total Vol Before Valve Total Vol After Valve 6.3 8.5 2.1 12.7 6.3 23.3 gals gals gals gals gals gals Minimum Pump Requirements Design Flow Rate Total Dynamic Head 10.5 13.9 gpm feet 0 4 8 12 16 0 50 100 150 200 250 Net Discharge (gpm) PumpData PVA1005 High Head Effluent Pump 10 GPM, 1/2HP 115V 1Ø Legend System Curve: Pump Curve: Pump Optimal Range: Operating Point: Design Point: Orenco Systems® Inc. , 814 Airway Ave., Sutherlin, OR 97479 USA • 800-348-9843 • 541-459-4449 • www.orenco.com NTD-SF-VA-1 Rev. 2.0, © 03/17 Page 1 of 2 Distributing Valves Technical Data Sheet General Orenco’s Automatic Distributing Valve Assemblies are mechanically operated and sequentially redirect the pump’s flow to multiple zones or cells in a dis- tribution field. Valve actuation is accomplished by a combination of pressure and flow. They allow the use of smaller horsepower pumps on large sand filters and drainfields. For example, a large community drainfield requiring 300 gpm (18.90L/sec) can use a six-line valve assembly to reduce the pump flow rate requirement to only 50 gpm (3.14L/sec). Orenco only warrants Automatic Distributing Valves when used in conjunc- tion with High-Head Effluent Pumps with Biotube® pump vaults to provide pressure and flow requirements, and to prevent debris from fouling valve operation. An inlet ball valve, a section of clear pipe, and a union for each outlet are provided for a complete assembly that is easy to maintain and monitor. Ideal valve location is at the high point in the system. Refer to Automatic Distributing Valve Assemblies (NTP-VA-1) for more information. Standard Models V4402A, V4403A, V4404A, V4605A, V4606A, V6402A, V6403A, V6404A, V6605A, V6606A. Product Code Diagram Materials of Construction All Fittings Sch. 40 PVC per ASTM specification Unions Sch. 80 PVC per ASTM specification Ball Valve Sch. 40 PVC per ASTM specification Clear Pipe Sch. 40 PVC per ASTM specification Applications Automatic Distributing Valve Assemblies are used to pressurize multiple zone distribution systems including textile filters, sand filters and drainfields. Bottom View Side View Top View Clear pipe Ball valve Elbow Coupling Distributing valve Union Elbows Assembly Available discharge connections: 4 = 4 available connections 6 = 6 available connections Inlet/outlet size, in. (mm): 4 = 1.25 (32) 6 = 1.50 (40) Distributing valve Discharge connections installed: 02 = 2 connections 03 = 3 connections 04 = 4 connections 05 = 5 connections 06 = 6 connections V A Orenco Systems® Inc. , 814 Airway Ave., Sutherlin, OR 97479 USA • 800-348-9843 • 541-459-4449 • www.orenco.com NTD-SF-VA-1 Rev. 2.0, © 03/17 Page 2 of 2 Technical Data Sheet Specifications Model Inlet Size, in. (mm) Outlets Size, in. (mm) Flow Range, gpm (L/sec) Max Head, ft (m) Min. Enclosure* V4402A 1.25 (32) 1.25 (32) 10 – 40 (0.63 – 2.52) 170 (51.816) VB1217 V4403A 1.25 (32) 1.25 (32) 10 – 40 (0.63 – 2.52) 170 (51.816) VB1217 V4404A 1.25 (32) 1.25 (32) 10 – 40 (0.63 – 2.52) 170 (51.816) VB1217 V4605A 1.25 (32) 1.25 (32) 10 – 40 (0.63 – 2.52) 170 (51.816) RR2418 V4606A 1.25 (32) 1.25 (32) 10 – 40 (0.63 – 2.52) 170 (51.816) RR2418 V6402A 1.50 (38) 1.50 (38) 15 – 100 (0.95 – 6.31) 345 (105.16) RR2418 V6403A 1.50 (38) 1.50 (38) 15 – 100 (0.95 – 6.31) 345 (105.16) RR2418 V6404A 1.50 (38) 1.50 (38) 15 – 100 (0.95 – 6.31) 345 (105.16) RR2418 V6605A 1.50 (38) 1.50 (38) 15 – 100 (0.95 – 6.31) 345 (105.16) RR2418 V6606A 1.50 (38) 1.50 (38) 15 – 100 (0.95 – 6.31) 345 (105.16) RR2418 * When using an enclosed basin, choose the next larger-sized diameter. 0 5 10 15 20 25 30 35 0510 15 20 25 30 35 40 45 50 55 60 65 70 V4600A V4400A V6600A V6400A Flow (gpm)Head Loss through Assembly (ft)Table 1. Automatic Distributing Valve Assembly Headloss Equations Model Series Equation Operating Range, gpm (L/sec) V4400A HL = 0.085 x Q1.45 10 - 40 (0.63 – 2.52) V4600A HL = 0.085 x Q1.58 10 - 25 (0.63 – 1.57) V6400A HL = 0.0045 x Q2 + 3.5 x (1 - e-0.06Q) 15 - 70 (0.95 – 4.42) V6600A HL = 0.0049 x Q2 + 5.5 x (1 - e-0.1Q) 15 - 70 (0.95 – 4.42)