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Call Before You Dig!. Eric Regensburger Montana DEQ Method for Estimating Attenuation of Nutrients from Septic Systems (MEANSS) (OR.

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Presentation on theme: "Call Before You Dig!. Eric Regensburger Montana DEQ Method for Estimating Attenuation of Nutrients from Septic Systems (MEANSS) (OR."— Presentation transcript:

1 Call Before You Dig!

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

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)

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6 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

7 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 ( 40 %). Distance to receiving/perennial SW is from GIS

8 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

9 Percent Nitrogen Load Reduction Soil Drainfield Soil Type within 100’ of surface water Distance to surface water (ft) 0AA0 – B 101 – CB501 – 5,000 30DC5,001 – 20, D20,001+

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

11 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

12 MEANSS RESULTS

13 THE END ….

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