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Sarah Mosley


Municipal Guide To Clean Water: Conducting Sanitary Surveys to Improve Coastal Water Quality

How is GIS used to identify potential pollution sources?

W i t h i n 7 5 o f a S t r e a m W i t h i n 2 5 0 o f a S e c o n d a r y W e t l a n d W i t h i n 2 5 0 o f T i d a l Z o n e W i t h i n 2 5 0 o f a n I m p e r v i o u s S u r f a c e W i t h i n 2 5 0 o f a W a t e r b o d y W i t h i n a F l o o d Z o n e W i t h i n 2 5 0 o f a P r i m a r y W e t l a n d W i t h i n 2 5 0 o f R i v e r S l o p e > 2 0 % W i t h i n 2 5 0 o f C o a s t

Overlaying multiple data sets can highlight patterns or potential and actual hotspots within the watershed. The examples presented here focus on watershed areas and on subsurface wastewater disposal systems, but this model can be applied to agriculture and other land uses as well as potential offshore sources to investigate relationships between land use and river monitoring sites, or between shoreline monitoring data and offshore activities.

This figure illustrates how GIS technology was used to identify preliminary hotspot areas within the wa- tershed. Watershed characteristics were integrated to highlight areas needing further investigation.

Similar to the example above, GIS can be used to specifi- cally target subsurface wastewater disposal systems (septic systems) within the watershed and their potential pollution risk. The visual representation of this information can be use- ful and the selected parcels can be downloaded into a table format to be shared with local plumbing inspectors, etc.

Note that the same criteria used to rank the watershed ar- eas can be applied to parcels with subsurface wastewater dis- posal systems. Additional files/criteria that would be useful and were not used in this example include potential problem parcels (parcels with corrective action required, agricultural parcels, campgrounds). The more detailed information (i.e., age of system, last time it was pumped out), the more useful the septic system ranking effort will be in prioritizing the first “tier” of properties to survey.

Additional resources:

Price, M. 2004. Mastering ArcGIS, Third Edition. New York: McGraw-Hill.

Reid, D., E. Just, G. Krauss and J. Robinson. Clean Beaches: Using GIS to Help Remedy Shoreline Contamination. Santa Barbara County Public Health Department & Geodigital Mapping, Inc. http://gis.esri.com/ library/userconf/proc00/professional/papers/PAP546/p546.htm

Kelsey, H., D.E. Porter, G. Scott, M. Neet and D. White. 2004. Using geographic information systems and regression analysis to evaluate relationships between land use and fecal coliform bacterial pollution. Journal of Experimental Marine Biology and Ecology 298:197-209

York Maine GIS Web site: http://www.yorkmaine.org/Default.aspx?tabid=59

Biddeford Maine GIS Web site: http://www.biddefordmaine.org/index.asp?Type=B_ BASIC&SEC=%7BC26FCDEE-AC34-41B1-9B9D-C9B3893CEC07%7D

ME DEP GIS Data and Maps: http://www.maine.gov/dep/gis/datamaps/index.htm#Google- Earth-Maps

Sarah Mosley

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