Citation:

WYMER, L. J. THE EMPACT BEACHES: A CASE STUDY IN RECREATIONAL WATER SAMPLING. Chapter 7, Larry Wymer (ed.), Statistical Framework for Recreational Water Quality Criteria and Monitoring. John Wiley and Sons, LTD, , Uk, , 113-134, (2007).

Impact/Purpose:

The objectives of this research are: (1) to evaluate rapid state-of-the-art measuement methods of pathogens that may indicate the presence of fecal pollution in recreational waters (beaches); (2) to obtain, jointly with a sister laboratory (NHEERL), a new set of water quality data and related health effects data at a variety of beaches across the U.S., in both marine and non-marine waters; (3) to analyze the research data set to evaluate the utility of the tested measurement methods, the new EMPACT monitoring protocol, and the health effects data / questionnaire, in order to establish a relationship between measured pathogens and observed health effects; and (4) to communicate the results to the Office of Water in support of their efforts to develop new state and/or federal guidelines and limits for water quality indicators of fecal contamination, so that beach managers and public health officials can alert the public about the potential health hazards before exposure to unsafe water can occur.

Description:

Various chapters describe sample and experimental design, use of a geometric mean or an arithmetic mean, modeling and forecasting, and risk assessment in relation to monitoring recreational waters for fecal indicators. All of these aspects of monitoring are dependent on the spatial and temporal distribution of fecal indicator bacteria in the water. Knowledge of the distribution of indicator bacteria in water is particularly important in sampling design for monitoring. The U.S. Environmental Protection Agency (EPA) conducted intensive water sampling studies during the summer of 2000 at five beaches in order to characterize temporal and spatial distribution of fecal indicator bacteria within the bathing areas of these beaches (Wymer et al., 2005, hereafter referred to as the EMPACT report). Study beaches encompassed a variety of environments (Table 1). During the months of July and August in 2000, water samples were collected at least twice daily from each of nine "fixed" locations in the water, as determined by a transect and zone (Figure 1). A transect consisted of an imaginary line through a fixed point on the beach perpendicular to the shoreline. A zone (or "depth zone") was defined as a contour line of equal water depth. As illustrated in Figure 1, each sampling location was defined by the intersection of transect and zone on a grid comprising three transects and three zones projected on the water's surface. A random point along the shoreline within the recognized beach area was selected to define the first transect (the leftmost transect in Figure 1). The middle transect was, then, determined as the parallel to the first transect at a distance of 20 meters, and the remaining transect, as the parallel to the middle transect at an additional distance of 20 meters, or 40 meters from the first transect. Locations at which the water attained a constant depth of 0.15, 0.5, and 1.3 meters (1.0 meters at Belle Isle, since buoys demarcating the swimming area were located at approximately this depth), corresponding to "ankle deep", "knee deep," and "chest deep" water, were selected as sampling zones. Because three of the beaches were affected by ocean tides, the actual geographic locations of these zones varied according to the tide stage. Hence, sampling locations at these beaches were fixed only in the sense that they correspond to locations at which the water depth was constant. Note the use of the term "zone" rather than "depth" in referring to areas of different water depth. This is to avoid confusion between water depth, which defines the sampling locations in Figure 1, and sampling depth, the depth below the surface of the water from which the samples were taken. In knee deep and chest water, the sampling depth was nearly always 0.3 meters from the surface, which is approximately "face deep" for a swimmer. A relatively small number of samples were taken from other sampling depths as part of a parallel study. Zones may be considered as roughly corresponding to different activities among bathers, mainly wading and infant or toddler bathing (ankle deep water), play (knee deep), and swimming or diving (chest deep).

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