St. Albans Town and City Subwatershed Mapping & Analysis

St. Albans, VT- 2009-2011
Contact: Mr. Allen Robtoy, City of St. Albans; P: (802) 524-1500

St. Albans Town and City Subwatershed Mapping & AnalysisWCA performed an intensive desktop and field analysis of the St. Albans Town and City stormwater management systems to evaluate contributing drainage to surface, stormwater, and combined sewer systems, and to develop a GIS database of this information. WCA coordinated with both Town and City Public Works and State of Vermont project partners to identify priority subwatershed areas, defined as areas of interest for future stormwater retrofits. WCA mapped the priority subwatersheds with refined field-survey techniques, and produced a final GIS dataset and map layout of the City drainage system. Lakeside Environmental Group provided subcontracting services, assisting with field-data collection and subwatershed mapping.

As a component of the Town mapping effort, WCA coordinated with the VT Agency of Transportation (VTrans) to acquire GIS mapping data covering median and cross- drainage systems along Interstate 89. WCA mapped the contributing subwatershed area for each median drainage inlet to develop a comprehensive subwatershed database covering the linear drainage system. The purpose of this refined mapping effort was to provide base information for evaluating retrofits of the median drainage system for enhanced treatment and detention of highway discharges.

A summary of key tasks completed by WCA are as follows:

  • I-89 median and cross-drainage system subwatersheds were mapped and analyzed by WCA for possible retrofit.
  • Existing stormwater permits and associated site plans and details were reviewed for a large portion of the Town and City to guide subwatershed mapping.
  • WCA coordinated with the VT DEC to map impervious area; this data was integrated into the final subwatershed mapping data layer.
  • Outfalls and stormwater and sewer infrastructure was mapped in the field with GPS equipment.
  • WCA conducted an analysis of subwatershed maps and recommended priority study areas based on stormwater retrofit potential. Key parameters considered for priority area identification included overall impervious area, percent impervious area, and land ownership.

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