MAHB MODEL
WATER SUPPLY PROTECTION REGULATION
[adopted by town of Plainville]
developed by William Dome P.E.
3.1 PURPOSE
These rules and regulations have been adopted to protect the water supplies of the residents of [TOWN] from excessive contamination of nitrate and other harmful chemicals resulting from the subsurface discharge of wastewater effluent. Nitrate contamination of drinking water is a serious public health problem. Nitrate also may serve as an indicator of other groundwater degradation associated with the use of household and industrial chemicals, pesticides, solvents, and other toxic substances. Therefore, the presence of those other substances may be presumed to be present also, when more than natural background levels of nitrate occur. Subsurface wastewater disposal, without nitrogen removal, is a major source of nitrate- nitrogen loading in the ground water and surface waters.
These rules and regulations shall also protect surface and groundwater from excessive nitrate-nitrogen and other nutrient loading and will retard the process of eutrophication of the lakes and ponds.
By requiring sufficient dilution of nitrates as well as these other byproducts of human activity, they may be decreased to a level which does not constitute a threat to the public health. Adequate land area surrounding a subsurface sewage disposal system will result in the dilution of the subsurface sewage discharge to levels of contaminants that will not constitute a treat to public or environmental health.
The Town of [TOWN] derives its water supply from groundwater. The groundwater supplies both the public water system and individual on-site wells. The groundwater of the Town of [TOWN], and the surface waters which contribute to the ground water constitute its water supply. Therefore, this regulation shall apply to any subsurface wastewater disposal system located within the Zone of Contribution of a public water supply well, located in an area of private well supplies, located within the watershed of [NAME Lake, NAME Lake] , or any other pond in the Town of [TOWN], or within the watershed of any stream which drains into said lakes and ponds.
This regulation shall not apply for the repair of existing septic systems where there is no increase in wastewater flow or there is no change of use. It shall not apply where there is connection to town sewer.
3.2 REQUIREMENTS
The applicant for construction of any subsurface wastewater system in the town, except for repairs of existing systems which have failed and are not being enlarged to provide for additional building construction or use, shall submit a GROUNDWATER IMPACT REPORT ( GIR) to the Board of Health. In the case of a subdivision, the GIR shall be submitted at the time of submittal of the preliminary plan. In case of lots not requiring approval as a subdivision, the GIR shall be submitted at the time of application for a Disposal Works Construction Permit.
3.3 METHOD OF CALCULATION.
The GIR shall be based on the following methodology for determination of nitrate loading which is based on procedures that have been accepted by and have been adopted and used by governmental planning agencies, enforcement agencies, and the U.S Geological survey. The GIR shall determine whether or not the proposed project will cause unacceptable ground water quality at the project boundary limits for the proposed use, based on the expected nitrate-nitrogen loading. The calculations shall follow the guidelines contained herein, using data which is appropriate for the Town of [TOWN].
The maximum allowable calculated concentration of nitrate-nitrogen within each project boundary shall be five (5) milligrams per liter in Zone II of the Public Water Supply and areas of private on-site well water supplies. It shall be seven and one-half (7 1\2) milligrams per liter in all other areas within the town.
CRITERIA AND FORMULA ASSUMPTIONS
NITRATE NITROGEN MAXIMUM ALLOWABLE CONCENTRATION (NMAX) AT PROJECT BOUNDARY :
At project boundary:
5 milligrams per liter in Zone II for the Public Water Supply.
5 milligrams per liter for areas of private wells.
7.5 milligrams per liter for all other areas.
In the case of multi-structure or multi-lot 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.
In the case of multi-structure or multi-lot 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.
ASSUME COMPLETE MIXING AND STEADY STATE
(EQUILIBRIUM) CONDITIONS.
CONTAMINANT ATTENUATION IS CAUSED BY DILUTION ONLY.
EVAPOTRANSPIRATION FROM SEPTIC SYSTEMS IS 10 PERCENT.
PRECIPITATION RECHARGE TO GROUNDWATER:
Nitrate-Nitrogen Concentration – 0.05 milligrams per liter
Quantity: Inches per Year Soil Percolation Rate
Minutes per Inch
19 Less than 2
17 2 to 4.9
15 5 to 9.9
13 10 to 14.9
11 15 to 19.9
9 20 +
0 Impervious areas with no recharge
Wetlands shall be considered having a percolation rate greater than 20 minutes
per inch for this calculation purpose.
WATER SUPPLY:
Town water: Nitrate-Nitrogen Concentration – 2.5 milligrams per liter
Private Water: 5 milligrams per liter
HOME SEPTIC SYSTEM:
Nitrate-Nitrogen Quantity – 5 pounds per person per year
Quantity of sewage – 55 gallons per person per day
Persons per household – 3
LAWN FERTILIZER
1.2 pounds of nitrogen per 1000 square feet of lawn per year. This is an estimated mean considering homeowner application, professional application, and lawns that are not fertilized.
Average lawn size: 10% of lot area unless specifically known.
OTHER:
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.
MIXTURE FORMULA FOR NITROGEN LOADING
( Rc times Rv ) + ( Nt ) + Lt
Wc = ————————————–
Rv + ( 0.9 times Sv ) + Vv(1)
Where:
Wc = Nitrate Nitrogen concentration in the groundwater
Rc = Nitrate Nitrogen concentration in the rain
Sc = Nitrate Nitrogen concentration in septic effluent
Rv = Volume of Recharge from rainfall
Sv = Volume of septic system effluent
Lt = Amount of nitrate nitrogen from lawn fertilizer and other sources
Vv = Volume of any other recharge waters
Nt = Amount of nitrate nitrogen in septic system effluent
( 5 pounds per person per year for a dwelling. Sc times Sv for other types of facilities )
3.4 SEVERABILITY