New Hampshire Small MS4 General Permit
Resources relating to the New Hampshire Small MS4 General Permit and where to go if you need additional information.
EPA NH Small MS4 General Permit
Additional information about the New Hampshire MS4 General Permit along with the full version of the permit, can be found on the EPA NH MS4GP webpage
Disclaimer: EPA is the permitting authority for the MS4GP. NHDES does not have any regulatory authority over the MS4GP and solely provides support for permittees.
The MS4GP was reissued by EPA on January 18, 2017. The final permit reflects modifications to the 2013 Draft Small MS4 General Permit and the 2015 renoticed permit sections. EPA proposed modifications to the 2017 NH MS4 General Permit on April 23, 2020 and finalized those modifications on December 7, 2020. Small MS4 owners and operators in urbanized areas (based on 2010 census) are required to apply or reapply for coverage under the 2017 MS4GP, unless granted a waiver by EPA.
The owners/operators of Small MS4s may include municipalities; county facilities, such as prisons/hospitals; districts; federal facilities, such as military bases; and state facilities, such as highways. The MS4GP requires MS4 operators to develop a stormwater management program that controls pollutants from all of the MS4 discharge points to the “Maximum Extent Practicable.” The MS4GP requires that the stormwater program include the six minimum control measures listed below as well as an annual report to EPA summarizing progress toward achieving specific measurable goals:
- Public education and outreach on stormwater impacts.
- Public involvement/participation during program development.
- Illicit discharge detection and elimination.
- Construction site storm water runoff control.
- Post-construction storm water management in new development and redevelopment.
- Pollution prevention/good housekeeping for municipal operations.
NH MS4 Regulated Area Maps Based off the 2020 Census Data
The information below helps to clarify how EPA has determined the new MS4 regulated areas for the next version of the NH MS4 Permit. The new MS4 regulated areas, which can be found in the resources created by NHDES on each permittee's permittee specific resources page, were created using the following process:
In a June 2023 final rule, EPA clarified that new Small MS4 designations will be based on whether the previously unregulated MS4s are located in urban areas with a population of 50,000 or more people. The clarification was necessary because the designation criteria in the Phase II regulations had previously been based on the location of “urbanized areas” (defined as urban areas with a population of 50,000 or more people), and the Census Bureau announced in March 2022 that it would no longer provide mapping information on such urbanized areas. The final rule ensures that the automatic designation criteria for MS4s remains the same as it has since the start of the Phase II program. Additional information about this process can be found on EPA's Urban Area Maps webpage.
The identification of newly designated Small MS4 regulated areas based on the 2020 Census data has been developed using the following information: current urban areas and their associated populations. Following is some additional information from EPA for reference and use:
1. Census 2020 Urban Area Reference Maps – The urban areas are shown in blue on the map which can be zoomed into in order to locate your state and/or urban area of interest.
2. Census 2020 Urban Population Data – The population data are contained in an Excel file which lists the urban areas and their respective populations per state. This data considers populations of 50,000 or more people.
The GIS file that was developed by NHDES to create the new MS4 area maps are available to download.
**Please note that the maps based on the 2020 Census data is for informational purposes only and should not be used to meet the current requirements authorized under the 2017 NH Small MS4 General Permit.**