Section 250-RICR-150-10-6.45 - Nitrogen Loading in Areas of Onsite Drinking Water WellsA. Applicability - For all OWTS applications for New Building Construction and for Alterations to a Structure, the design flow for an OWTS shall not exceed three hundred forty-five (345) gallons per day per twenty thousand (20,000) square feet of applicant's lot area where the property utilizing the OWTS or any adjacent lot is served by an onsite drinking water well (public or private), or if there is a drinking water well within two hundred feet (200') of the proposed OWTS, except as provided for below in §§ 6.45(B) and (C) of this Part. The Director may require this standard to be met for OWTS Applications for Repair in areas where the groundwater is shown to exceed the Preventive Action Limit for nitrate of five (5) mg/l, pursuant to Subchapter 05 Part 3 of this Chapter, Groundwater Quality Rules. The three hundred forty-five (345) gallons per day per twenty thousand (20,000) square feet loading limitation is equivalent to approximately one sixth of an acre (1/6) of applicant's lot area per bedroom. This rule applies to all OWTS except those subject to the requirements of § 6.39 of this Part. Applicants must still meet all CRMC established density and other requirements where applicable. Compliance with § 6.45 of this Part does not relieve applicants of the nitrogen reducing technology requirements in § 6.43 of this Part.B. Design Flow Calculation - The three hundred forty-five (345) gallons per day per twenty thousand (20,000) square feet design limit may be exceeded for OWTSs utilizing nitrogen reducing technology. The allowed design flow with a nitrogen reducing technology is derived using the equation in § 6.45(C) of this Part or read from § 6.45(D) of this Part. For the purposes of § 6.45 of this Part, there are no limits on the design flow of OWTSs with nitrogen reducing technologies that are approved by the Director as meeting the nitrogen standard of ten (10) mg/l.D. Nitrogen Loading Nitrogen Removal (Percentage) | Effluent Nitrogen Concentration (mg/l) | Maximum Design Flow per 20,000 sq. ft. (gpd) |
50 | 19 | 690 |
66 | 13 | 1015 |
75 | 10 | 1380 |
E. Exceedance of Design Flow Calculation - The three hundred forty five (345) gallons per day per twenty thousand (20,000) square feet design limit or other design limit utilizing nitrogen reducing technologies pursuant to § 6.45(B) of this Part may be exceeded by the establishment of nitrogen credit land meeting the requirements of § 6.45(F) of this Part under the following circumstances: 1. For subdivisions - The design limit must be met over the entire area of the subdivision. This can be met by designating portions of the subdivision as nitrogen credit land.2. For individual lots - The design limit can be calculated by establishing adjacent properties as nitrogen credit land with the consent of the property owner.F. Nitrogen Credit Land - Nitrogen credit land cannot be designated on land that is already being used to meet the nitrogen loading requirements for an OWTS approved by the Director. Nitrogen credit land must be restricted by a deed restriction, conservation easement, or other appropriate legal instrument recorded in the municipal land evidence records such that:1. Addition of nitrogen from wastewater discharge, nitrogenous fertilizer (synthetic or natural), and raising and grazing livestock is prohibited; and2. Impervious surfaces, which reduce recharge, including paved streets, paved parking areas, and structures are prohibited.250 R.I. Code R. 250-RICR-150-10-6.45
Amended effective 11/25/2018
Amended effective 12/28/2021
Amended effective 7/1/2022