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OWTS Design Considerations Under Reg. 43 - Major Changes and Highlights

Explore significant changes and highlights in OWTS design regulations under Reg. 43, focusing on system operation and maintenance oversight. Learn the impact of new regulations on design scenarios.

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OWTS Design Considerations Under Reg. 43 - Major Changes and Highlights

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  1. Presented by: Chuck Cousino,Onsite Wastewater Treatment System Coordinator, CDPHE To: 2014 CPOW Annual Conference Date: January 17, 2014 OWTS Design Considerations Under Reg. 43

  2. Questions that need to be addressed: • What are the major changes to the Regulations relative to OWTS design? • How do these changes effect what I do? Walk-through various design scenario’s

  3. What Are some Major Changes in the new Regulations? • A major step toward “Performance Based Standards”. • (Let’s call them “Advanced Prescriptive”) • Allow for expanded design options to overcome site specific restrictions (may vary; local code decisions) • Allow for reduction in system size by incorporating proven technologies that reduce organic loading (local code decisions) • Requires enhanced OWTS system operation & maintenance oversight

  4. Reg. 43 Highlights • Bed systems : Maximum width allowed will be 12’ (unless TL2+ or in repair situations; Local decision) • Trench length may now be 150’ if pressure distribution is utilized (Upon local approval) • Maximum depth to the soil treatment interface is 48” from ground surface • Percolation tests can still be conducted; However, now specific requirements on “how” they should be conducted. • Refer to section 43.5(D) • Focus on Long Term Acceptance Rate (LTAR) vs. only the percolation rate (Table 10.1) • How many Gallons/Sq.Ft./Day will this soil accept ?

  5. Reg. 43 Highlights, cont. • A “Visual and Tactile” evaluation of the soils shall be conducted • Shall be conducted by a “competent technician “. • Optional until July 1, 2016; then required; (allows for a training period) • Focus on soil structure; Redoxymorphic features; restrictive layers; other visual items Under ISDS, we used a… Soil Profile Hole

  6. New Term:Soil Profile Test Pit Excavations “Visual & tactile” evaluation of the soil

  7. STRUCTURE

  8. With all of this said… We need to realize that the majority of septic systems that will be installed in the upcoming years will most likely be “conventional gravity on-site wastewater treatment systems”. Properly sited, properly installed, properly maintained, a conventional gravity OWTS can be the best option for many sites

  9. Many feel that their septic system is “working” if they flush, and it goes where…. However, lets be mindful that… AWAY !! Is the system really functioning (treating), or are just making sure that it goes away ? We can do a better job of designing, installing and operating our Onsite Wastewater Treatment Systems.

  10. How do these changes effect what I do? Reg. 43, Basic Design 101 Class; ISDS vs. OWTS Let’s see how the designs compare… What has changed???

  11. High Mountain Rd. • Old ISDS Design • Rock and PipeTrench Installation • System Sizing; Daily Flow • 4 Bedrooms x 150 = 600 gpd • 600 gpd x 1.5 = 900 gpd = Q • Percolation Rate = “t” = 25 mpi • Q x square root “t” • A = • 5 • 900 25 • A = = 900 Sq.Ft. • 5 • Trench size: 3’ x 60’ = 180 Sq.Ft. • 5 trenches x 180 = 900 Sq.Ft. • Note: Some Counties have additional requirements for proposed S.T.A. ie: Garbage disposal, Washing machine, etc… {900 x 1.6 = 1440 sq.ft. req.} Well 100 4-Bedroom Home 99 1,250 Gal. Septic Tank 60’ 98 Replacement Area 97

  12. High Mountain Rd. Well 100 • Old ISDS Design • “ Smallest footprint” • Chamber Trench Installation @ 900 Sq.Ft. • ISDS Guidelines allows 50% Reduction in a chamber trench; (900 x 0.5) = 450 Sq.Ft. • Using a Quick 4+ Standard Chamber, Providing 11.55 Sq.Ft./Chamber • Chamber Calculation: • 450 / 11.55 = 39 Chamber Units Req’d. • 3 Trenches at 52’; 13 Chambers/Trench • However… 4-Bedroom Home 99 1,250 Gal. Septic Tank 52’ Replacement Area 98 97

  13. High Mountain Rd. • Old ISDS Design • “Largest footprint” • “Possible requirements” • If local H.D. requires additional Sq.Ft. for garbage grinders, washing machines, etc.. (900 x 1.6) = 1440 Sq.Ft. • & • If local H.D. only allows a 40% Reduction for a chamber trench; (1440 x 0.6) = 864 Sq.Ft. • & • Used a Quick 4 Plus Low Profile Chamber, • Provides for 10.00 Sq.Ft./Chamber • Chamber Calculation: • 864 / 10.00 = 87 Chamber Units Req’d. • 5 Trenches at 72’; 18 Chambers/Trench • We just went from 39 to 87 Chambers Well 100 4-Bedroom Home 99 1,250 Gal. Septic Tank Replacement Area 98 72’ 97

  14. High Mountain Rd. • Old ISDS Design • If a “Bed /Chamber” system is proposed • Best Case: • ISDS Guidelines allows 40% Reduction in a bed; (900 x 0.6) = 540 Sq.Ft. • Quick 4 Plus Standard Chamber • Provides for 11.55 Sq.Ft. • 540 / 11.55 = 47 Chamber Units Req’d. • Worst Case: • If the 1.6 factor was applied; and only a 25% reduction given, then 1080 Sq.Ft. Req’d. • 1080 / 11.55 = 94 Chamber Units Req’d. Well 100 4-Bedroom Home 99 1,250 Gal. Septic Tank 15’ Replacement Area 98 30’ 12’ 92’ 97

  15. Notable Changes • Old ISDS Design • Design Flows: 4 Bedrooms x 150 = 600 gpd 600 gpd x 1.5 = 900 gpd • Percolation Rate = “t” = 25 mpi Q x t • Formula for Area Req’s. A = 5 • Possible Additional Sq.Ft. Requirements ( x 1.6 ) • Reductions allowed for chambers 25%, 40%, 50% …. • Varied Sq.Ft. / Chamber Calc’s. • Regulation 43 • Design Flows: (Suggested) 150 gpd for first 3 bedrooms 75 gpd for each additional bdrms • Perc Rate; related to a defined Soil Type; (Table 10.1; Soil Type 2) • Long Term Acceptance Rates; (Table 10.1) • Additional Safety Factors Eliminated • Reductions are more defined; dependant on “Methods of Application” (Table 10.2 & 10.3) • Chamber sizing given a standard 0.7 reduction (Table 10.3)

  16. Table 10-1 Soil Treatment Area Table 10-1: Soil Treatment Area Long-Term Acceptance Rates by Soil Texture, Soil Structure, Percolation Rate, Treatment Levelby Soil Texture, Soil Structure, Percolation Rate and Treatment Level

  17. STA Adjustments– Methods of ApplicationTable 10-2 (All TLs)

  18. STA Adjustments– Methods of ApplicationTable 10-3 (TL1 only)

  19. High Mountain Rd. • New Reg. 43 Design • System Sizing; Daily Flow • 4 Bedroom Home • (3 x 150) + (1 x 75) = 525 gpd • Q = 525 gpd • 16 – 25 min./inch perc = Soil Type 2 • Treatment Level 1, Long Term Acceptance Rate (LTAR) for Soil Type 2 = 0.6 Gal/Sq.Ft./Day • Gallons/Day • A = • LTAR (Gal./Sq.Ft./Day) • 525 • A = = 875 Sq.Ft. • 0.6 • 875 Sq.Ft. of Soil Treatment Area (S.T.A.) required. But… • Need additional information… Well 100 4-Bedroom Home 99 1,250 Gal. Septic Tank ? 98 Replacement Area 97

  20. High Mountain Rd. • New Reg. 43 Design • 875 Sq.Ft. of S.T.A. Required • Utilize Table 10.2: (Which can be used for “ALL” treatment levels) • Gravity (Sq.Ft. x 1.0) • Pump or Siphon (Sq.Ft. x 0.9) • Pressure Dosed (Sq.Ft. x 0.8) • Our system is “Gravity” • 875 x 1.0 = 875 Sq.Ft. • But… Still need additional information… Well 100 4-Bedroom Home 99 1,250 Gal. Septic Tank ? 98 Replacement Area 97

  21. High Mountain Rd. • New Reg. 43 Design • 875 Sq.Ft. of S.T.A. Required • Utilize Tables 10.3: (For TL1 only) • Rock & Pipe (Sq.Ft. x 1.0) • - Mfgr. Media (Sq.Ft. x 0.9) • Chambers (Sq.Ft. x 0.7) • Chamber calc’s. simplified… • REG. 43: “If the width of the chamber is within 90% of the width of the excavation, it may be approved for the equivalent width of the excavation”. • Note: All chambers 4’ long x 33”-36” wide are calculated at 12.0 Sq.Ft./Chamber. ( ie: 33/36 = 0.92 ) • Therefore, all of the sq.ft. calculations for each specific chamber models is now gone. Well 100 4-Bedroom Home 99 1,250 Gal. Septic Tank ? 98 Replacement Area 97

  22. High Mountain Rd. • New Reg. 43 Design • Chamber Trench Installation: • 875 Sq.Ft. of S.T.A. Required • Design Assumption: • Utilize Tables 10.2: • Gravity (Sq.Ft. x 1.0) • = 875 Sq.Ft. x 1.0 = 875 Sq.Ft. • Utilize Tables 10.3: • Chambers (Sq.Ft. x 0.7) • = 875 Sq.Ft. x 0.7 = 613 Sq.Ft. • Chamber Calculation: • 613 / 12.0 = 51 Chamber Units • (Use 52 to provide equal length; 13 chambers / trench) • Again note: All of the 1.5 and 1.6 multipliers/safety factors are gone ! Well 100 4-Bedroom Home 99 1,250 Gal. Septic Tank 52’ Replacement Area 98 97

  23. High Mountain Rd. • New Reg. 43 Design • Chamber Bed Installation: • 875 Sq.Ft. of S.T.A. Required • Design Assumption: • Utilize Tables 10.2: • Gravity (Sq.Ft. x 1.2) • = 875 Sq.Ft. x 1.2 = 1050 Sq.Ft. • Utilize Tables 10.3: • Chambers (Sq.Ft. x 0.7) • = 1050 Sq.Ft. x 0.7 = 735 Sq.Ft. • Chamber Calculation: • 735 / 12.0 = 62 Chamber Units • Again note: All of the 1.5 and 1.6 multipliers/safety factors are gone ! Well 100 4-Bedroom Home Bed 99 1,250 Gal. Septic Tank 84’ Replacement Area 9’ 98 97

  24. OWTS Sizing Comparison Old ISDS Regulations Regulation 43 Requirements 4 Bedroom home = 525 gpd Chambers: Requires 613 sq.ft. S.T.A. (Gravity / Trench) 51 Chamber units (at 12.0 sq.ft. / chamber) Req’d. Bed system: S.T.A. Req’d. = 735 sq.ft. 62 Chamber units (at 12.0 sq.ft. / chamber); Max. 12’ wide. • 4 Bedroom home = 600 gpd • Requires between 450 1440 sq.ft. S.T.A. (Trench) • 29 87 Chamber Units Req’d. • Bed system: • S.T.A. Req’d. = 540 1080 sq.ft. • 47 108 Chamber Units Req’d.

  25. Regarding OWTS Design, Regulation 43…. • Provides for more Consistent and Uniform Design • Looks at Both Soil Texture and Structure • Focuses on Long Term Acceptance Rates, And Ultimately…. • Focuses on Wastewater Treatment

  26. Next…… • Roger Shafer will take our design to the next level • How to design for a more difficult site; using the options provided for in Reg. 43 • QUESTONS ?? Thank You!

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