RIPDES Stormwater Regulation Glossary

Census Designated Places (CDPs) means those that are delineated for the Decennial Census as the statistical counterparts of incorporated places. CDPs are comprised of densely settled concentrations of population that are identifiable by name, but are not legally incorporated places. To qualify as a CDP, an unincorporated community must meet the following criteria:

(i) 1,000 or more persons if outside the boundaries of an urbanized area (UA) delineated for the subsequent special census;

(ii) 2,500 or more persons if inside the boundaries of an urbanized area (UA) delineated for subsequent census;

(iii) 250 or more persons if outside the boundaries of an urbanized area (UA) delineated for the subsequent special census, and within the official boundaries of an American Indian reservation recognized for the 1990 census.

Densely Populated Area (DPA) means a census designated place(s) as defined by the latest Decennial Census that is located outside the urbanized area and meets all of the following criteria:

(i) The population density within the census designated place is equal to or greater than 1,000 people per square mile; and

(ii) The census designated place has or is part of a block of contiguous census designated places with a total population of at least 10,000 people.

Illicit discharge means any discharge to a municipal separate storm sewer that is not composed entirely of storm water except discharges pursuant to a RIPDES permit (other than the RIPDES permit for discharges from the municipal separate storm sewer) and discharges resulting from fire fighting activities.

Impaired Waters , for the purposes of Rule 31 of the RIPDES Regulations, means those waters within the State, which do not currently meet Rhode Island Water Quality Standards as identified in the latest list of Impaired Waters compiled by the Office of Water Resources (OWR) of the Rhode Island Department of Environmental Management and is referred to as the State of Rhode Island's 303(d) list.

Large municipal separate storm sewer system means all municipal separate storm sewers that are either:

(i) Located in an incorporated place with a population of 250,000 or more as determined by the 1990 Decennial Census by the Bureau of Census (Appendix G, RIPDES Regulations); or

(ii) Located in the counties listed in Appendix I, RIPDES Regulations except municipal separate storm sewers that are located in the incorporated places, townships or towns within such counties; or

(iii) Owned or operated by a municipality other than those described in Rule 31(b)(7)(i) or (ii) of the RIPDES Regulations and that are designated by the Director as part of the large or medium municipal separate storm sewer system due to the interrelationship between the discharges of the designated storm sewer and the discharges from municipal separate storm sewers described under Rule 31(b)(4) (i) or (ii) of the RIPDES Regulations. In making this determination the Director may consider the following factors:

(A) Physical interconnections between the municipal separate storm sewers;

(B) The location of discharges from the designated municipal separate storm sewer relative to discharges from municipal separate storm sewers described in paragraph (b)(4)(i) of this section;

(D) The nature of the receiving waters; and

(E) Other relevant factors.

(iv) The Director may, upon petition, designate as a large municipal separate storm sewer system, municipal separate storm sewers located within the boundaries of a region defined by a storm water management regional authority based on a jurisdictional, watershed, or other appropriate basis that includes one or more of the systems described in Rule 31(b)(4)(I), (ii), (iii) of the RIPDES Regulations.

Major municipal separate storm sewer outfall (or "major outfall") means a municipal separate storm sewer outfall that discharges from a single pipe with an inside diameter of 36 inches or more or its equivalent (discharge from a single conveyance other than circular pipe which is associated with a drainage area of more than 50 acres); or for municipal separate storm sewers that receive storm water from lands zoned for industrial activity (based on comprehensive zoning plans or the equivalent), an outfall that discharges from a single pipe with an inside diameter of 12 inches or more or from its equivalent (discharge from other than a circular pipe associated with a drainage area of 2 acres or more).

Major outfall means a major municipal separate storm sewer outfall.

Medium municipal separate storm sewer system means all municipal separate storm sewers that are either:

(i) Located in an incorporated place with a population of 100,000 or more but less than 250,000, as determined by the 1990 Decennial Census by the Bureau of Census (Appendix H, RIPDES Regulations); or

(ii) Located in the counties listed in Appendix J, RIPDES Regulations, except municipal separate storm sewers that are located in the incorporated places, townships or towns within such counties; or

(iii) Owned or operated by a municipality other than those described in Rule 31(b)(7)(i) or (ii) of the RIPDES Regulations and that are designated by the Director as part of the large or medium municipal separate storm sewer system due to the interrelationship between the discharges of the designated storm sewer and the discharges from municipal separate storm sewers described under Rule 31(b)(7)(i) or (ii) of the RIPDES Regulations. In making this determination the Director may consider the following factors:

(A) Physical interconnections between the municipal separate storm sewers;

(B) The location of discharges from the designated municipal separate storm sewer relative to discharges from municipal separate storm sewers described in Rule (b)(7)(i) of the RIPDES Regulations;

(D) The nature of the receiving waters; or

(E) Other relevant factors.

(iv) The Director may, upon petition, designate as a medium municipal separate storm sewer system, municipal separate storm sewers located within the boundaries of a region defined by a storm water management regional authority based on a jurisdictional, watershed, or other appropriate basis that includes one or more of the systems described in Rule 31(b)(7)(i), (ii), (iii) of the RIPDES Regulations.

Municipal separate storm sewer means a conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains):

(i) Owned or operated by a city or town or the State district association, or other public body (created by or pursuant to State law) having jurisdiction over disposal of sewage, industrial wastes, storm water, or other wastes, including special districts under State law such as a sewer district, flood control district or drainage district, or similar entity, or an Indian tribe or an authorized Indian tribal organization, or a designated and approved management agency under section 208 of the CWA that discharges to waters of the State;

(ii) Designed or used for collecting or conveying storm water;

(iii) Which is not a combined sewer; and

(iv) Which is not part of a Publicly Owned Treatment Works (POTW) as defined in Rule 3 of the RIPDES Regulations.

Municipal separate storm sewer system (MS4) means all separate storm sewers that are defined as "large" or "medium" or "small" municipal separate storm sewer systems pursuant to Rule 31(b)(4), (b)(7), and (b)(17), or designated under Rule 31(a)(1)(vii) and (a)(1)(viii) of the RIPDES Regulations.

Outstanding National Resource Waters (ONRWs) means water of National and State Parks, Wildlife Refuges, and other such waters designated as having special recreational or ecological value as defined in the State of Rhode Island Water Quality Regulations.

Regulated small municipal separate storm sewer system (regulated small MS4) means a small MS4 that meets the requirements of Rule 31(a)(5)(i) of the RIPDES Regulations.

Small municipal separate storm sewer system (small MS4) means all separate storm sewers that are:

(i) Owned or operated by the United States, a state, city, town, borough, county, parish, district, association, or other public body (created by or pursuant to State law) having jurisdiction over disposal of sewage, industrial wastes, storm water, or other wastes, including special districts under State law, such as a sewer district, flood control district or drainage district, or similar entity, or a designated and approved management agency under section 208 of the CWA that discharges to waters of the United States.

(ii) Not defined as "large" or "medium" municipal separate storm sewer systems pursuant to Rule 31(b)(4) and (b)(7) of the RIPDES Regulations.

(iii) This term includes systems similar to separate storm sewer systems in municipalities, such as systems at military bases, large hospital or prison complexes, and highways and other thoroughfares. The term does not include separate storm sewers in very discrete areas, such as individual buildings.

Special Resource Protection Waters (SRPWs) means surface waters identified by the Director as having significant ecological or recreational uses, as defined in the State of Rhode Island Water Quality Regulations and listed in Appendix D of those regulations.

Urbanized Areas (UAs) means those areas that are comprised of one or more places ("central places") and the adjacent densely settled surrounding territory ("urban fringe") that together have a minimum of 50,000 persons. The urban fringe generally consists of contiguous territory having a density of at least 1,000 persons per square mile. The complete criteria are available from the U.S. Bureau of the Census at https://www.census.gov/geo/reference/ua/urban-rural-2010.html.