Runoff Controls

Manchester's Storm Water Management Program (SWMP) requires all construction sites, that will disturb one or more acres of land, assure that all measures are being taken to greatly reduce site erosion and subsequent sediment runoff.

Construction site runoff controls are an important part of this program as erosion can add several hundred thousand tons of sediment to the waterways within Manchester annually. This sediment covers the plankton food source and fish breeding grounds on the bottom of the rivers, lakes, ponds and streams. The food chain is disrupted as there is no available food source for the microorganisms, small organisms, and very small fish. Once these small organisms and fish are starved out the larger fish populations begin to die off as well as the food source is severely reduced or eliminated.

A heavy rain can move large amounts of sediment onto beds where fish, turtles and frogs have recently laid their eggs. This sediment can completely cover these eggs and eliminate many potential births that would eventually populate the shores of these areas.

Best Management Practices are the Key

Contractors, Developers, and Owner/Operators of construction sites are expected to use Best Management Practices (BMPs).

BMPs not only require the proper initial installation of structural measures such as silt fences, temporary detention basins, catch basin silt inserts, and erosion mats, but require the ongoing maintenance of such structures.

Contractors are required to develop a Storm Water Pollution Prevention Plan (SWPPP) that is approved by the City and outlines the BMPs that are going to be used. The SWPPP must also outline the sequence of construction activity, structural unit maintenance, and site inspection schedules to assure all are installed correctly and maintained properly.

The following links give much greater detail on BMPs and the requirements of a SWPPP. The City believes these sites provide good examples of what is expected from the implementation of BMPs and how to structure a sound SWPPP.

EPA's BMPs for Stormwater Phase II
State of New Hampshire BMPs
International Stormwater BMP Database
California Stormwater Quality Associations's Handbook for Construction Site BMPs
U.S. DOT Guide to BMPs
NH Stormwater Manual
EPA Guide to Developing a SWPPP
Overview of Minnesota's Construction Stormwater Permit
National Resource Defense Council Stormwater Fact Sheet