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Call Before You Dig!

Call Before You Dig!. Method for Estimating Attenuation of Nutrients from Septic Systems (MEANSS) (OR THE ARTIST FORMERLY KNOWN AS “ SNoRES ”). Eric Regensburger Montana DEQ e regensburger@mt.gov. WHY MEANSS??. Estimate septic loading for TMDL’s

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Call Before You Dig!

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  1. Call Before You Dig!

  2. Method for Estimating Attenuation of Nutrients from Septic Systems (MEANSS) (OR THE ARTIST FORMERLY KNOWN AS “SNoRES”) Eric Regensburger Montana DEQ eregensburger@mt.gov

  3. WHY MEANSS?? • Estimate septic loading for TMDL’s • Estimate septic loading for Nutrient Trading (DEQ-13) • Need for a simple method that uses site-specific info known to control denitrification • Lack of available tools for estimating septic contributions to surface water……

  4. OTHER TOOLS • ArcNLET: GIS based, ground water travel time, user-defined denitrification • STUMOD: Spreadsheet, detailed chemical/physical process, can use all default or site-specific parameter, N reduction below drainfield only • SWAT: Complex model with biozone function (N reduction below drainfield only), can add user defined denit. rate • WAG – Wild A#% Guess (my favorite)

  5. PARAMETERS • Three Variables: • Hydrologic Soil Group (HSG) at drainfield • Distance to nearest perennial surface water • HSG in 100 foot riparian buffer • Variables receive %N reduction score • Add up the 3 values for total reduction • Assumes the complete volume of effluent reaches surface water (SW) • Assumes simple flow direction to SW

  6. DATA SOURCES • Drainfield location from GIS: search “Montana Structures Framework” (drainfield location ~ residence) • HSG is from NRCS STATSGO(2) OR SSURGO • HSG used to classify runoff potential • 4 HSGs – A,B,C,D: low to high clay content (<10, 10-20, 20-40, >40 %). • Distance to receiving/perennial SW is from GIS

  7. A LITTLE MORE DETAIL….. • Denitrification occurs in soils with high organic content, anoxic, and time for reaction to occur >>> HSG best commonly available data to estimate that. • Travel distance easier to measure than travel time. • Improve MEANSS accuracy: • Measure soil carbon content • Measure travel time instead of distance • Accurate flow direction for distance

  8. Stream 100 ft 450 ft C soil @ d.f. = 20% B soil @ riparian =20% 450 ft. to stream = 10% Reduction: 20+20+10=50% Group B Soil Group C Soil Drainfield

  9. COMPARISONS/VALIDATION • Compared to 5 studies that measured N in ground water • Montana(2), Wisconsin(2), Nevada(1) • MEANSS estimated N load was 68%, 74%, 82%, 83% and 120% of the comparable loads measured in studies. • In process of validating to a SWAT model for Prickly Pear drainage south of Montana City

  10. MEANSS RESULTS

  11. THE END ….

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