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Water Quality Committee of Friends of Sligo Creek |
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Is Sligo Creek Safe? |
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Where to Report Pollution Problems |
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How to Help Sligo Water Quality |
Sligo Creek's water quality is affected by being in a heavily paved, urbanized area. High quality stream water is cool and rich in dissolved oxygen, on which fish and aquatic insects depend. It is relatively free of suspended materials such as sand or mud and toxic chemical inflows. Presently, Sligo Creek's temperature spikes during rainstorms as the heat and chemicals on roofs and parking lot surfaces is transferred to stormwater entering the creek. This rapid runoff causes severe erosion to the stream bed, making the creek turbid with suspended sediment. The erosion exposes adjacent sewer pipes to the force of the stream and can cause the sewer pipes to leak directly into the creek. The best hope for reducing these problems affecting Sligo Creek's water quality is the increased use of good stormwater management practices in the watershed.
| Parameter | Maryland State Standard | Sligo Creek |
|---|---|---|
| Temperature | Less than 32.2° C (90° F) at any time | Meets standard |
| Turbidity | May not exceed levels detrimental to aquatic life; turbidity resulting from discharges may not exceed 150 units at any time or 50 units as a monthly average. | Turbidity standard breached during stormwater events See Recent Breaches |
| Bacteria | Steady state geometric mean indicator density: Enterococci bacteria ≤33 E. coli bacteria ≤126 Maximum allowable density for infrequent full body contact recreation: Enterococci bacteria = 151 E. coli bacteria = 576 |
Sligo sites usually exceed standard levels See Sligo Bacteria Levels |
| pH | Never less than 6.5 or greater than 8.5 at any time | pH standard sometimes breached See Recent Breaches |
| Dissolved Oxygen | Never less than 5 mg/L at any time | See Recent Breaches |
Other evidence for this, from studies by other organizations:
"Of the three major tributaries surveyed, Wheaton Branch exhibited the lowest baseflow dissolved oxygen (DO) levels. Violations of Maryland Department of the Environment's (MDE) 5.0 mg/L DO criteria were recorded at Wheaton Branch on four out of the 30 sampling dates (5/23/94, 6/18/94, 6/22/94, and 6/9/95). The lowest stream DO concentration observed during the study 2.87 mg/L, was recorded on 6/18/94 approximately 250 meters downstream of the Wheaton Branch stormwater management facility (SWM). While some aquatic can tolerate low dissolved oxygen levels (or even anaerobic conditions) for show periods, concentrations of 6.0 mg/L or higher are often required for long term survival."¹
Sligo Creek received a poor rating at all tested sites based on surveys of bottom dwelling stream insects in 2004, 2006, and 2008 for the Maryland Stream Waders program. This means that the population of bottom dwelling aquatic non-backboned creatures was found to be lacking in variety and abundance, and that few types of pollution sensitive macroinvertebrates were found in Sligo Creek.
Sligo Creek similarly received a poor rating in previous macroinvertebrate surveys.
Pesticides
The U.S. Geological Survey sampled Sligo Creek for pesticides in August 1994. The concentrations of pesticides found in the single sample didn't break any known Environmental Protection Agency standards, but little is known about the effects of pesticide mixtures. Here is an attempt at evaluating pesticide levels in Sligo Creek.
Email: Water Quality Committe Chair
