Overview of Beach Water Quality

Transcription

1 Overview of Beach Water Quality

2 MDC Beach Monitoring Program MDC monitored Harbor beaches weekly during summer months since 1973; daily beginning in 1996 Samples analyzed for two indicator bacteria: fecal coliform (until 2001) and Enterococcus ( current)

3 In 1996, MDC/MWRA began special study to monitor four Boston Harbor beaches daily to better understand variability in water quality and to develop predictive tools to help managers Constitution Beach in E. Boston Carson Beach in S. Boston Tenean Beach in Dorchester Wollaston Beach in Quincy

4 Charles R BOSTON EAST BOSTON Inner Harbor Constitution Beach Carson Beach Boston Harbor Tenean Beach Neponset R. QUINCY Wollaston Beach

5 Pollution sources Storm drains CSOs Illicit sewer connections Boats Animal waste (birds, dogs)

6 Study results All beaches showed great variability in water quality and differed in their response to rainfall Carson Beach had the best bacterial water quality Tenean Beach and Wollaston Beach had the worst bacterial water quality; storm drains are likely culprits

7 Water quality criteria overview Massachusetts Department of Environmental Protection: State water quality criteria for Class SB (swimmable/fishable): Fecal coliform geometric mean of 200 colonies/100 ml AND no more than 10% of samples exceed 400 col/100 ml

8 Compliance with SB criteria Fecal coliform Constitution Carson Tenean Wollaston Geometric mean 200) No more than 10% below % 6% 16% 19%

9 Water quality criteria, cont. EPA Criteria for designated bathing beach, marine water Enterococcus 30-day running geometric mean 35 colonies/100 ml AND single sample 104 colonies/100 ml

10 Water quality criteria, cont. Department of Public Health (MDC following these guidelines) Enterococcus 5-day running geometric mean 35 colonies/100 ml AND single sample 104 colonies/100 ml

11 Compliance with DPH/EPA criteria Enterococcus Constitution Carson Tenean Wollaston Geometric mean ( 35) Percent meeting single sample max ( 104) % 94% 87% 85%

12 MDC posting criteria Prior to 2001, MDC posted a swimming advisory if, at two of the three locations: Fecal coliform counts from previous day exceeded 200 colonies/100 ml OR Enterococcus counts from previous day exceeded 104 colonies/100 ml

13 MDC posting criteria, cont. Beginning in 2001, MDC posted a swimming advisory if, at any location: Enterococcus count from previous day exceeds 104 colonies/100 ml OR 5-day geometric mean Enterococcus exceeds 35 colonies/100 ml OR heavy rainfall predicted or occurred previous day/night

14 Boston Water and Sewer CSO Storm drain Sampling location Reserved Channel South Boston Carson Beach McCormack Bathhouse BOS084 BOS085 BOS086 BOS087 I Street BOS083 BOS082 M Street BOS081 Dorchester Bay Pleasure Bay Savin Hill

15 Carson Beach: Percent of weekly samples failing to meet posting limits, % 40% 30% 20% 10% 0% Fecal coliform Enterococcus Summer Rainfall (in.)

16 Carson Beach: Response to rainfall Mean ln(enterococcus) EPA single sample limit for designated swimming area (104 cfu/100 ml) EPA geometric mean limit for designated swimming area (35 cfu/100 ml) > hour rainfall (in.)

17 Weather condition and water quality Weather condition Percent of samples failing to meet standard Of samples that fail, proportion of samples in each weather condition Dry/Damp 4% 62% 10% 10% In total, 58 out of 1005 samples failed to meet the standard Light Rain Heavy Rain 22% 28% All weather 6% 100% 36 of these samples were in dry weather, 22 in wet weather

18 Summary Rainfall does affect water quality, but it is not the only cause of elevated bacteria counts. Most high bacteria counts occur in dry or damp weather. But, compared to dry weather, wet weather samples have a greater proportion of high bacteria counts Other factors also play a role: dry weather contamination (illicit sewer connections), animal waste, tidal influences

19 Summary At Carson Beach, 22 out of 1005 samples, or 2.1% of samples failed to meet the Enterococcus standard in wet weather The infrequency of rain events (and infrequent high counts during/after the rain event) make it difficult to evaluate relationship of rainfall and high counts using daily monitoring alone.

20 Ongoing projects M&E storm monitoring MWRA low-tide monitoring evaluating dry-weather effects BWSC repair of illicit sewer connections