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Contaminant Inventory

The inventory of the delineated zones comprising a source water protection area (SWPA) can be the most time intensive of the five steps. A potential contaminant source inventory identifies all contaminant sources and land uses in the delineated area and shows their locations in relation to the well or intake as an overlay on the base map. Some sources may be obvious like above ground storage tanks, landfills, livestock confinement areas, highway or railroad right of ways and sewage treatment facilities. Others are harder to locate like abandoned cesspools, underground tanks, french drains, dry wells and wells or old dumps and mines.

The Safe Drinking Water Act requires the Source Water Assessment Program provide both an inventory and susceptibility assessment to each public water system. While this effort will focus on contaminant sources deemed by DEP to be significant, a community-generated inventory can be more inclusive and more useful for the type of management approach to be used.

Many communities have found existing citizen groups to be the best volunteers. For example, a senior citizen group may know the history of the community, are known and trusted by members of the community, and may have the time to do the necessary property inspections and interviews. You may also interest a local high school science class in assisting with the inventory effort. The use of an existing group may reduce the amount of time you need to spend in getting things organized.

Placing the compiled inventory information on the base map allows the team to see the number, location and type of potential contaminant sources that exist in the SWP area. Understanding the relationship of inventoried sources to the well or intake is important in deciding on the best management options. Some community planning teams have noted that the inventory step generates considerable paperwork. It is important that all land uses within the SWPA are identified for the effort to be of value.

A community generated inventory process starts by locating lists of contaminant sources compiled by federal, state, and local agencies. Locations are marked on the base map (sites are visited as needed to fill in data gaps). Next, an inventory of Zone I (for groundwater) and Zone A (for surface water) is completed, usually by the certified operator since he/she is usually very familiar with the area immediately around the well or intake. Identified land use and contaminant sources of concern that are located in this zone are also marked on the base map. Then, a combination of visual survey, mail survey or site visit is used to identify significant land uses and contaminant sources within Zone II/Zone B. Finally, potential contaminant sources in Zone III/Zone C are inventoried using an appropriate method. Potential contaminant sources in these regions are prioritized based on an assessment of the susceptibility of the source water. Usually, all land uses and selected contaminant sources are identified on the base map.