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Water Quality Testing Results

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Texas Surfrider Foundation

P.O. Box 563

Liberty TX 77575

Lili at Surfside

Assessment of Beach Water Quality in Texas
Chris Clodfelter, Applied Hydrology Associates

Presented at Emerging Technologies, Tools, and Techniques To Manage Our Coasts in the 21st Century, January 28-31, 2003, Cocoa Beach, Florida, sponsored by U.S. Environmental Protection Agency

Introduction

The Texas coast consists of 367 miles of shoreline along the Gulf of Mexico. The gulf beaches are primarily located on barrier islands although some mainland shorelines are present on the upper coast. More than one-third of the stateâs population and 70% of its economic activity are located within 100 miles of the Texas coastline. There are 12 Texas counties with gulf beaches and regular water quality monitoring currently takes place in six of these counties.

Monitoring of water quality with respect to the human pathogen indicator enterococci bacteria is currently performed along the upper coast (Jefferson, Galveston and Brazoria counties) and along the lower coast (Nueces and Cameron counties). No monitoring currently takes place along the central coast (coastal bend) area. The locations currently monitored are those counties with gulf beaches most heavily used for recreational purposes. The entities performing the monitoring include those funded by the Texas General Land Officeâs (GLO) administration of a USEPA BEACH Act grant (Texas Beach Watch) and the Surfrider Foundation. The Texas Beach Watch program was initiated in August 1998 but terminated several months later due to a lack of funding. The program was started again on a limited basis in late 2000 and the BEACH Act grant provided additional funding in 2002. The Beach Watch groups performing the monitoring include:

Jefferson County ö The Center for Coastal and Marine Studies at Lamar University

Galveston County ö Galveston County Health Department

Brazoria County ö Brazoria County Health Department

Matagorda County ö Lower Colorado River Authority

Nueces County ö Nueces County Parks and Recreation Department

Cameron County ö Coastal Studies Laboratory at the University of Texas ö Pan American

The Matagorda County data is not included in this assessment. The program data for this county was not of sufficient quality and quantity to evaluate at this time.

Description of Study Area

The monitoring area includes approximately 26 miles of the 367 miles of Texas coastline. About 150 miles of the Texas coast are currently undeveloped and covered by the Coastal Barriers Resources Act. The counties included in this study are shown in Figure 1. The Jefferson County sites are located on a mainland shoreline and the beaches consist of a thin veneer of sand overlying mud. The area is undeveloped with the exception of state park facilities and scattered oilfield production facilities. The Galveston County sites are all located on barrier islands with the exception of one bay beach (Texas City Dike). Development in these areas is moderate (Crystal Beach and Capline/Gilchrist) to dense residential (West End) and high density commercial along the seawall section in Galveston. The Texas City Dike itself is undeveloped with the exception of a fishing pier at one end and small restaurants and bait shops at the other end. The dike is located in an area with heavy industry and residential development nearby. The monitored beaches in Brazoria and Nueces counties are also located on barrier islands and are developed residential areas with some tourism based development. The beaches in Cameron County are heavily developed residential and commercial (tourism related) with the exception of Boca Chica which is a state park.

Methodology

The data reviewed for this study included Beach Watch data from 67 sites (1910 total samples excluding duplicates) and Surfrider data from 3 sites in Galveston County (57 samples). The number of samples per county (exclusive of the duplicates) are shown in Figure 2. Samples were collected approximately weekly from May through September at the Beach Watch sites. Some of the Beach Watch sites have data beginning to January and extending into November. Surfrider sites were sampled approximately weekly from March through October with the exception of September when no samples were collected.

All samples were analyzed for the enterococci indicator. Beach Watch samples from all counties except Brazoria and Cameron were analyzed using membrane filtration (EPA Method 1600). The samples from these counties were analyzed using substrate technology tests (Enterolert ®), according to American Public Health Association (1995) procedures using a Quanti-Tray sealer (IDEXX Laboratories). The Surfrider samples were analyzed using Enterolert and the 5-tube method with a 10:1 dilution.

Figure 1. Texas coastline with sampled counties highlighted

Figure 2. Number of samples collected per county during study period

Data Assessment

The analytical results were compared to GLO and EPA guidelines. The GLO Beach Watch program entails issuing advisories, in the form of posted signs, when criteria are exceeded. Only the county health departments have the authority to actually close beaches. The GLO uses a public advisory criteria density of 104/100 ml enterococci count in an arithmetic mean of two site samples or if the arithmetic mean of all samplings at a site within 30 days exceeds 35/100ml. These criteria are similar to the EPAâs criteria of a single sample exceedance of 104/100ml or a 30-day 5 sample average of 35/100ml. The differences are that the GLO program requires collection of two samples at each site in order to assess daily exceedances and the 30-day average is based on total number of samples (not necessarily 5) collected in a 30-day period.

Discussion of Results

The data were first used to compare the daily sample GLO guidelines (mean of two samples) with the single sample EPA guidelines. This was done to establish similarities between the two guidelines. Figure 3 shows this comparison and it is evident that although the number of exceedances are similar, analysis of just one sample can lead to a slightly higher number of exceedance days.

Figure 3. Comparison of EPA single sample exceedance to GLO 2-sample average exceedance

The data were also evaluated with respect to temporal variability. Figure 4 shows that in the period covered by the study that the greatest number of exceedances occurred during the month of September. September in Texas saw the end of the dry summer and the beginning of a period of wet weather associated with tropical depressions and hurricanes. Most of the wet weather was focused on the upper coast and thus a higher number of exceedances occurred in Galveston and Brazoria counties. It is interesting to note that Jefferson County, although located on the upper coast, did not show a higher number of exceedances during the month of September. This is likely due to the area receiving runoff from areas less urbanized than the Galveston-Brazoria area.

Figure 6 shows the total relative number of exceedances for the monitored counties. These data are normalized for the number of samples collected. The data show that the counties located on the upper coast (Jefferson, Galveston, Brazoria) have a greater issue with beach water quality than the counties on the lower coast. This is likely due to the greater population density on the upper coast.

Figure 5. Temporal variability of exceedances

The relationship between the number of sample exceedances and the population is shown in Figure 7. This analysis shows a good correlation between the population within a 50-mile radius and the number of sample exceedances. Comparison of the number of exceedances with population density within 10-mile and 20-mile radii did not produce such a good correlation. This may indicate that beach water quality is related to more regional effects rather than localized sources of water quality degradation.

Figure 8 shows the percentage of samples exceeding the 30-day criteria. These criteria were difficult to evaluate because there were a number of 30-day periods in which less than 5 samples were collected. The data indicate results similar to the single day exceedance criteria in that most of the exceedances were located on the upper coast during the late summer months.

Figure 6. Normalized relative number of exceedances on a county basis

Figure 7. Correlation of number of exceedances with population density

Figure 8. Percentage of county sites exceeding the 30-day criteria

The Florida Department of Health utilizes an enterococci range that is useful for comparing the relative water quality. This water quality classification is as follows:

0-34/100 ml = good
35-103/100ml = moderate
>104/100ml =` poor

This same classification system proves useful in assessing the relative water quality along the Texas coast. Figure 9 shows the overall water quality for all the monitored counties. This analysis shows that for the most part the beach water quality in Texas, with respect to enterococci counts, is good at least 75% of the time. The data from the remainder of the monitoring period shows the quality equally divided between moderate and poor. Figure 10 shows graphs of the same criteria but on a county basis. These graphs support what has been discussed previously, that is, the areas with the most beach water quality degradation are those locations nearest the population and industrial centers. Galveston County obviously has the most frequently degraded water quality and Brazoria County follows close behind. Brazoria County, although not necessarily more developed along the coast then some of the lower coast counties, receives runoff from the Houston-Galveston area from the Brazos River and bayous that discharge into the western reaches of Galveston Bay.

Figure 9. Water quality data with respect to assessment categories

Figure 10. Relative water quality on a county basis

Summary

The data show that the beach water quality along the Texas coast can be categorized as good with respect to the enterococci indicator. Exceedances of both EPA and GLO criteria do occur along the coast. These occurrences take place primarily in the months with higher precipitation and in those locations closer to population and industrial centers. These locations are primarily Galveston and Brazoria counties, which are located along the upper coast. It is also the upper coast beaches, primarily the Galveston County beaches, that receive the highest number of visitors and beach users.

References

American Public Health Association, 1995, Standard Methods for the Examination of Water and Wastewater, 18th ed., Eaton, A.D., Clesceri, L.s., and Greenberg, A.E. (eds.), Washington, DC.