Last Updated 08/25/2026
Merrimack Stormwater Laws & Regulations
The Town of Merrimack regulations are compliant with the National Pollutant Discharge Elimination System (NPDES) through municipal regulation Merrimack Code Part II Chapter 167. The town’s Municipal Separate Storm Sewer System (MS4) requires Merrimack to administer and enforce compliance with stormwater discharge permits in an effort to decrease stormwater pollutants and increase overall water quality. The town is part of the Souhegan Watershed Association, which works collaboratively with other municipalities within the local watershed to improve and maintain the environmental quality of the Souhegan River and its watershed.
EXCERPT- Merrimack Stormwater Ordinances, May 2014
Chapter 167. Stormwater Management Standards
167-3. Applicability
Prior to disturbance, the responsible party shall submit a SWMP to the Community Development Department (CDD) for any tract(s) of land that results in a total disturbance of 20,000 or more square feet of land.
167-4. SWMP Requirements
B. Post-construction stormwater management.
- Design standards. Design of post-construction stormwater management shall be in accordance with, at a minimum, the design guidance set forth in the New Hampshire Stormwater Manual, which is hereby incorporated by reference.
- Post-construction meeting. The responsible part and its engineer or technical representative shall attend a post-construction meeting with CDD and DPW.
- Responsibility. The responsible party shall install, inspect, report, operate, and maintain any post-construction stormwater management and erosion control measures.
- Bond release requirements.
- Ongoing inspection and operational maintenance requirements for water quality measures required by the SWMP shall be a condition of site plan approval or, in the case of other development not subject to site plan approval, included as a covenant in the underlying deed(s).
- Attendance by the responsible party at a post-construction meeting.
- As-built plans bearing the seal and signature of a New Hampshire registered PE.
- Approval of the bond release by both CDD and DPW.
- Reporting. Each SWMP shall require annual site inspections by the responsible party that shall be documented and, at a minimum, include review of stormwater flow paths, accumulation of any sediment, condition of contaminant control devices, stormwater quality observations, corrective actions and time frames. All records of the inspections shall be submitted to CDD.
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Frequently Asked Questions
What size project triggers a Stormwater Management Plan in Merrimack?
Any tract of land facing a total disturbance of 20,000 square feet or more requires a SWMP submitted to the Community Development Department before disturbance begins.
What design standard does Merrimack require for post-construction stormwater management?
Post-construction stormwater management must follow, at minimum, the design guidance in the New Hampshire Stormwater Manual, which the town has incorporated by reference into its ordinance.
Who is responsible for maintaining post-construction stormwater measures in Merrimack?
The responsible party must install, inspect, report on, operate, and maintain any post-construction stormwater management and erosion control measures on their property.
What has to happen before a bond is released for a Merrimack stormwater project?
Several conditions must be met: ongoing inspection and maintenance requirements become a condition of site plan approval, or are written into the underlying deed for projects not subject to site plan approval; the responsible party and its engineer must attend a post-construction meeting with the Community Development Department and Department of Public Works; as-built plans must bear the seal and signature of a New Hampshire registered professional engineer; and both departments must approve the bond release.
What does Merrimack's annual stormwater inspection report need to cover?
The responsible party must document an annual site inspection covering stormwater flow paths, sediment accumulation, the condition of contaminant control devices, stormwater quality observations, and any corrective actions taken along with their timeframes. All inspection records get submitted to the Community Development Department.
The information on this page is provided for general informational purposes only and is not legal advice. Regulations change frequently — AQUALIS makes no warranty as to the accuracy or completeness of this content, and any reliance on it is at your own risk. Consult a qualified professional or your local regulatory authority to confirm requirements applicable to your specific property.
