CRITERIA AND FORMULA ASSUMPTIONS
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NITRATE NITROGEN MAXIMUM ALLOWABLE CONCENTRATION (NMAX)
AT PROJECT BOUNDARY:
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At project boundary:
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5 milligrams per liter in Zone II for the Public water supply.
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5 milligrams per liter for areas of private wells.
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7.5 milligrams per liter for all other areas.
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In the case of multistructure or multilot projects in Zone II
in areas of private wells, the maximum allowable concentration shall
be no greater than 7.5 milligrams per liter at any individual lot
line, but shall be no greater than (NMAX) at the project boundary.
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In the case of multistructure or multilot projects in all other
areas, the maximum allowable concentration shall be no greater than
10 milligrams per liter at any individual lot line, but shall be no
greater than (NMAX) at the project boundary.
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ASSUME COMPLETE MIXING AND STEADY STATE (EQUILIBRIUM) CONDITIONS.
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CONTAMINANT ATTENUATION IS CAUSED BY DILUTION ONLY.
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EVAPOTRANSPIRATION FROM SEPTIC SYSTEMS IS 10%.
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PRECIPITATION RECHARGE TO GROUNDWATER:
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Nitrate-Nitrogen Concentration — 0.05 milligrams per liter
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Quantity:
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Inches per Year
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Soil Percolation Rate Minutes per Inch
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---|---|---|---|
19
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Less than 2
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17
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2 to 4.9
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15
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5 to 9.9
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13
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10 to 14.9
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11
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15 to 19.9
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9
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20 +
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0
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Impervious areas with no recharge
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Wetlands shall be considered having a percolation rate greater
than 20 minutes per inch for this calculation purpose.
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WATER SUPPLY:
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Town water: Nitrate-Nitrogen Concentration — 2.5 milligrams
per liter
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Private Water: 5 milligrams per liter
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HOME SEPTIC SYSTEM:
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Nitrate-Nitrogen Quantity — 5 pounds per person per year
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Quantity of sewage — 55 gallons per person per day
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Persons per household — 3
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LAWN FERTILIZER
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1.2 pounds of nitrogen per 1,000 square feet of lawn per year.
This is an estimated mean considering homeowner application, professional
application, and lawns that are not fertilized.
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Average lawn size: 10% of lot area unless specifically known.
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OTHER:
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Criteria for uses or other criteria not included herein shall
be evaluated on a case-by-case basis according to criteria that is
acceptable to the Board of Health. Applicants should contact the Board
of Health office prior to conducting such calculations for the purpose
of establishing such other criteria.
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MIXTURE FORMULA FOR NITROGEN LOADING
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Wc =
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(Rc times Rv) + (Nt) + Lt
Rv + (0.9 times Sv) + Vv
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Where:
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Wc
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=
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Nitrate-nitrogen concentration in the groundwater
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Rc
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=
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Nitrate-nitrogen concentration in the rain
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Sc
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=
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Nitrate-nitrogen concentration in septic effluent
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Rv
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=
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Volume of recharge from rainfall
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Sv
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=
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Volume of septic system effluent
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Lt
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=
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Amount of nitrate-nitrogen from lawn fertilizer and other sources
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Vv
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=
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Volume of any other recharge waters
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Nt
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=
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Amount of nitrate-nitrogen in septic system effluent
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(5 pounds per person per year for a dwelling. Sc times Sv for
other types of facilities.)
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