X hits on this document

212 views

0 shares

0 downloads

0 comments

26 / 72

20

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

What are the current, wind, and wave conditions?

Nearshore currents affect the fate and transport of pollut- ants and are driven by wind, tides, and remote (offshore) forcing. The surf zone is the area between the shoreline and where the waves begin to break. It is the region where most recreational water contact occurs. If sources of contamina- tion are land-based, the surf zone generally has higher con- centrations of bacteria compared to offshore waters. Waves primarily control mixing and transport in the surf zone, and prevailing winds influence movement of water outside of this zone. Depending on the area, cross-shelf exchange may carry contaminants from a distant source to the surf zone.51

  • Note the water flow in the areas of the sanitary survey. Typically, areas with little water flow have higher concentrations of bacteria compared to areas with more water movement. Document the typical speed and direction of alongshore currents. This can help to assess the impact of a storm drain or river outlet located a short distance from the beach area. The volume of the “plume” of freshwater should also be considered. A flow meter can be used to determine the flow/velocity. An easy method of determining the speed and direction of water flow is to place a marked orange (or other “drifter”) in the water and record the travel time and distance.

The physical characteristics and oceanography of the shoreline can influence the temperature of the water and the amount of sunlight that penetrates the water.

Water temperature and sunlight play a key role in the activity, distribution, and persistence of marine organisms, and affect the rate of biological and chemical reactions. Each type of bacteria has an optimal temperature for growth; fecal indicator bacteria generally survive longer in colder waters compared to warmer waters.7, 52 However, warmer water may act as an indicator of polluted waters entering coastal waters via streams, rivers, and storm drains.31

Many studies have documented the effects of sun- light on bacteria levels in polluted estuaries and beaches. Bacteria can survive longer in turbid waters and in bottom sediments that are not as susceptible to UV radiation. Sun- light breaks down bacteria concentrations with a distinct diurnal pattern whereby levels are generally lower in the afternoon than in the early morning.31, 53

What to look for: 2. Wastewater disposal

Target human sources first! Human sewage can cause disease through indirect or direct body contact or inges- tion of contaminated water or shellfish, and is potentially more dangerous compared to non-human sources of fecal contamination. Studies have shown a strong link between contact with water polluted by human “point” sources of contamination and gastrointestinal (GI) illness.8, 9 Generally, human sources are easier to control compared to non-human sources of pollution.18 For these reasons, identifying sources of human sewage and wastewater is the priority target for a sanitary survey.

What properties are serviced by a publicly owned treatment works (POTW)? Are they properly connected?

  • Contact the town office or engineering department or DEP Wastewater Division to determine which properties along the shoreline and within the larger watershed are serviced by public utilities (municipal wastewater or sanitary sewer collection and treatment system).

Sometimes, structures that are supposed to be connected to the sanitary sewer have been wrongly connected to a storm sewer, or were never connected. Connections or sewer mains may also leak. Methods to check for leaks and cross-connections include on-site plumbing inspec- tions, introducing smoke or dye into the system, or using television cameras; these are discussed in detail in Part II. In some cases, the sewer lines have been mapped and transferred to digital files that can be used in GIS and other mapping software.

Are there publicly owned treatment works (POTW) outfalls and pump stations in the vicinity?

  • Note the presence of POTW outfalls that may

impact coastal waters.

The outfalls of POTWs are usually located far enough up- stream to provide dilution to within legal pollutant levels. However, POTW malfunctions have the potential to impair coastal water quality, in particular when high flows in the collection system during wet weather result in combined sewer overflows and sanitary sewer overflows. All POTWs

Document info
Document views212
Page views212
Page last viewedSat Dec 10 04:13:44 UTC 2016
Pages72
Paragraphs1816
Words29598

Comments