Congress tasked the U.S. Environmental Protection Agency under the Clean Water Act to clean up polluted waterways and make the water quality safe enough for uses including wildlife habitat, fishing, boating, swimming, shellfish harvesting, and irrigation. Approximately 40% of the nation’s waterways do not meet water quality standards and urban/suburban municipal stormwater runoff is one of the primary causes.
Following a rain or snowstorm event, precipitation flows over the ground. Impervious surfaces such as sidewalks, pavement, and buildings prevent the water from soaking naturally into the ground. Urban/suburban municipalities rely on a system of storm drainage pipes to carry the water to an outfall location at a waterbody such as a stream, brook or river. Before the precipitation enters the storm system, it flows over land picking up pollutants, chemicals, dirt, garbage, fertilizer, and oil. In areas that have no storm drainage system, the precipitation and what it collects might flow directly into a lake or stream.
To protect surface water quality, Congress instituted Phase I and II of stormwater permitting under The National Pollutant Discharge Elimination System (NPDES) to address the issues of stormwater runoff. Phase I started in 1990 and regulates cities and counties with populations of 100,000 that operate a municipal separate storm sewer system (MS4). Phase II started in March 2003 and regulates municipalities such as West Springfield that are within a U.S. Census urbanized areas (concentrated areas of development) also having a municipal separate storm sewer system (MS4). According to state-reported water quality information (2002 National Assessments Database, 305B report), urbanized high density municipal areas are a leading cause of water quality impairment.
The NPDES Stormwater Program requires regulated municipalities to obtain a permit from the U.S. Environmental Protection Agency and implement a stormwater management plan including best management practices to reduce pollutant runoff. As part of the permit, EPA established six minimum control measures for municipalities to meet the conditions for permit approval. These control measures are:
· Post Construction Stormwater Management
· Good Housekeeping / Pollution Prevention
West Springfield has instituted a stormwater management plan to address these issues. To meet the Illicit Discharge Detection and Elimination control measure, the town has invested significant resources into detecting illicit discharges and being able to identify possible source(s) of contamination. To help detect and identify sources of illicit discharges, the town is creating a system-wide storm drainage system map. This map will show the location of outfalls, which is where storm pipes discharge into a waterbody or waterway. The map will also show storm system pipes, catch basins, manholes, and other features to provide the ability to trace the
pipes upstream of the outfalls to the source(s) of contamination. In addition to mapping the storm drainage system, the town is mapping its sanitary sewer system to help in illicit discharge detection and/or overflows into the storm drainage system.
Mapping the storm and sewer systems involved creating digital flow maps from engineering plans using geographic information systems (GIS) software. Once the plans were in digital map format, field crews performed field validation on the data by GPS’ing features such as outfalls and updating these locations on the digital maps. Crews also performed extensive field work to confirm and determine the direction of flow between pipes and used dye and video testing when necessary. The town first piloted these efforts in an older urban part of town and then adopted a similar approach throughout the town. The mapping process generally followed this process:
· Convert engineering plans to electronic form
· Create database of engineering plans
· Build web-based application to search engineering plans
· Create digital maps of storm and sewer systems
· Attribute digitized features with feature information
· Field verify and update digitized features
· Dye and video test missing or conflicting feature information
As the features are being mapped, the outfalls are being inspected for possible illicit discharges. Information gathered from outfall testing will allow the town to detect, locate, and eliminate possible illicit discharges from the storm water system. The system-wide storm and sewer maps will provide accurately located structures to help the town immediately and more easily implement the Illicit Discharge Detection and Elimination program. The maps will provide the town the ability to trace pipe connections upstream of the outfall being investigated to help determine the source(s) of pollutants.
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