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Part II. Special Studies: Finding Bacteria Hotspots17, 23


The sections of this guide are not linear. Special studies may help pinpoint problem areas and verify pollution sources, but nothing can replace careful scrutiny of land use practices, especially properties with subsurface wastewater disposal (septic) systems. Depending on the watershed characteristics, it may be most useful to start with the wastewater disposal section in Part III. Re- viewing the methods of wastewater disposal and types of land use for all properties within the drainage area of concern, as described in Part III, will help narrow down the list of possible contributing sources and prioritize areas needing future action and remediation. As always, target human sources first!Think bang for the buck!

A special study refers to any monitoring, analysis and/ or research studies beyond routine monitoring of the shore- line area. There is no single, perfect method or indicator for tracking down sources of bacteria. Verifying the status of a potential source may require a combination of strate- gies. The goal of special studies is to find bacteria “hotspots” within the watershed that require further investigation.

Typically, sources of bacteria are not obvious and verify- ing the actual status of a potential pollution source requires a tool-box approach that integrates multiple resources. Methods of source tracking beyond initial property surveys may need to be employed. For example, intensive moni- toring upstream will help identify areas needing further investigation, followed by property surveys to identify potentially malfunctioning septic systems, and possibly dye tests to verify the malfunctioning status of the systems.

Note that verification of a problem is not always pos- sible. For example, effluent from a malfunctioning septic system may percolate quietly through soil into ground- water and adjacent water bodies. Similarly, dye testing of a malfunctioning system may never show visible dye in surface waters.

Sanitary survey work is a continuous process. While all sources of fecal contamination may not be identified,

Special Studies: Finding Bacteria Hotspots

the elimination of most human sources should result in a measurable improvement in water quality. The goal is to identify and remediate as many of those sources as pos- sible. Also, over time, systems that are currently working may malfunction in the future due to aging, changes in use (e.g., from seasonal to permanent residence), or inad-

equate maintenance.

For purposes of the guide, the same source tracking principles can be applied to relatively undeveloped areas and urban areas, to rivers and storm drainage networks. The following information is a brief overview of source tracking methods.

Visual field screening

High bacteria levels documented in freshwater outlets (e.g., river mouth, storm drain) along the shoreline war- rant moving inland to investigate contributing sources of bacteria. Field observation can spot obvious problems and will help identify additional “special study” monitoring lo- cations. Potential problem areas should be identified first and prioritized using drainage area and property maps in conjunction with a field screening by vehicle and on foot.

  • Conduct field screening during dry and wet weather. Bring a GPS unit to document the location of potential pollution sources and/or monitoring stations. For a storm drainage network, start by looking for discharge during dry weather, and gradually move up the network until the flow is no longer present. The goal is to isolate discharge areas within the larger storm drainage system. Changes in

Michelle Warneke


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