Stormwater Permit Requirements

MS4 Permit Timeline

In 2003, the EPA introduced the concept of Municipal Separate Storm Sewage System (MS4) Permits to guide authorities like the City of Portsmouth in managing their Clean Water Act requirements implementation. The State of NH MS4 Permit requirements were established by the NH Department of Environmental Services soon after.

A total of 60 communities in New Hampshire are currently subject to MS4 permit requirements. Of those, 16 received waivers. Portsmouth is one of the other 44 that must comply with MS4 -- although there are three areas covered by separate permits: NHDOT roadways through Portsmouth, UNH, andPease International Tradeport).

Each MS4 is intended to last for five years; but it was not until 2018 that the current permit replaced the original 2030 requirements. The City of Portsmouth's stormwater management plan is designed to ensure the City's water discharges comply with the current State of NH MS4 Permit requirements.

More Stringent Requirements

The new MS4 Permit looks more closely at water quality and the NHDES definitions for "impaired waters" that focus on total maximum daily loads (TMDL) allowed for nitrogen (high concentrations in fertilizer run-off), phosphorus, chloride (high concentrations in road salt), bacteria and metals. 

Portsmouth MS4 Permit Responsibilities:

1.Public Education/Outreach to residents, businesses, developers, industries

A minimum of two public outreach messages per year to the four audiences. 

Additional targeted messages regarding impaired-water contributing factors: 

Blue the Portsmouth DPW Stormwater Management Program mascot2.Public Participation/Involvement -- Think Blue!

  • Public information meetings
  • Adopt-A-Spot program particiation (including raingardens)

3.Illicit Discharge Detection & Elimination (IDDE) 

  • July 2019 written plan
  • Priority ranking of outfalls
  • Dry weather sampling
  • Catchment investigations of system connections
  • Map of entire storm system (10 year history)
  • Adequate legal authority to prohibit and investigate illegal connections

4.Construction Site Runoff Control  

  • Written procedures for site plan review for new sites larger than 1 acre
  • Written procedures for inspection and enforcement measures
  • Regulatory controls for other wastes such as demolition debris, litter, and sanitary wastes

5.Post‐Construction Stormwater Regulations

  • First 2 years for new or redeveloped sites over 1 acre = Enhanced stormwater treatment
  • Within 4 years = Update street and parking lot design to promote Low Impact Development and limit impervious cover and Inventory all City owned land for future retrofits
  • Within 5 years = Identify five sites for potential retrofit

6.Good Housekeeping -- City Operations and Facilities (within 2 years)

  • Develop Plan for municipal activities, street sweeping, catch basin cleaning, BMP inspections, etc.  
  • Inventory of publicly-owned facilities, including parks and open space, buildings and facilities, vehicles and equipment
  • Stormwater Pollution Prevention Plan (SWPPP) for DPW/transfer station facility  

Detection & Elimination of Reasons for Impaired Waters

Nitrogen

Next 4 years: 

  • Nutrient Source Identification Plan
  • Sources, load estimates, remedial measures
  • Targeted educational messages (pet waste and fertilizer management)
  • Enhanced street sweeping  

Within 5 years: 

  • Identify Potential Stormwater Retrofit Sites

Chloride

Salt Reduction Plan by Year 3.  

Fully implement by Year 5.

  • Tracking and reporting municipal use
  • Upgrade equipment to increase efficiency
  • Training for municipal staff
  • Update regulations for new and redeveloed sites to minimize salt usage.
  • Identify private parking lots with 10 or more parking spaces and encourage the use of  Green SnowPro operators

For a slide show summary of these initiatives, click here.