Water Sampling

Environmental Health Services (EHS) routinely conducts bacteriological sampling of many areas in an effort to provide information to the public on water quality and promote the safe use of these resources. View a map of the associated water sampling areas and locations. 
           
This sampling utilizes the bacteriological indicator organism Enterococci for salt water and Escherichia coli (E. coli) for fresh water. These organisms are found in the intestines of all warm-blooded animals and are important chiefly because, when found in higher concentrations in conjunction with a known or suspected source of sewage contamination, the probable presence of other more pathogenic organisms is indicated.

A history of sampling helps to provide some of the background information needed to evaluate long-term trends in water quality. Water conditions change constantly. It should be noted that any single sample or group of samples represents a “snap shot in time” and should not be used without other supporting information to characterize the water quality of a particular river, lake or bay. 

Water users should remember that all natural waters support many different microorganisms. Some of these organisms are pathogenic to humans; however, most are not. Water users should note that murky or debris-strewn water, which often occurs after violent storms or heavy rains, is a general indication of poor water quality. Excessive storm water runoff after heavy rains can carry pet waste, agricultural waste or fecal contaminants from brief sewage overflows as well as various chemicals including those associated with commercial and residential lawn care.

Swimmers, skiers, boaters or any one whose activities will bring them into close contact with natural waters should always take into consideration their own observations before entering the water. Natural waters should never be considered safe for ingestion.

Should sampling by the County measure elevated bacteriological levels due to a known or suspected sewage overflow, that would make water activities unsafe or unhealthy at a particular location, a water contact alert will be issued. In the event that these conditions affect a public bathing beach, that beach will be closed. The Water Contact Alert will be posted and a press release will be issued to major media outlets. Signage may also be posted at points of greatest access to the affected body of water.

In open waters, the public will be advised to minimize water contact and the health risks associated with sewage contaminated waters will be explained. After a water contact alert has been issued, the conditions, which may have contributed to poor water quality, will be investigated. After those conditions have abated, sampling will resume to determine when the water quality has improved to an acceptable level. The water contact alert will then be lifted.

When monitoring in open areas of water indicates a widespread, abnormal rise in the concentration of bacteria and there is no known or suspected sewer overflow, a Water Quality Advisory may be issued. These conditions are typically associated with storm water runoff. Water Quality Advisories are non-regulatory and usually temporary in nature. Advisories are issued to provide recommended precautions for recreational water users and applicable public health recommendations will be noted on this web site. Precautionary signage is not typically posted for Water Quality Advisories, however a press release may be issued if conditions are widespread and severe.

In an effort to inform the public regarding specific health related precautions, various types of signage may be found in and around access points to both fresh and tidal waters.

• Water Contact Alert—No Recreational Activities
• Recreational Water Quality Advisory
• Health Advisory—Baltimore Harbor
• Stream Sense
• Stream Sense Sign Locations

Baltimore County is required by the United States Environmental Protection Agency (USEPA) and the Maryland Department of the Environment (MDE) to take routine bacteriological samples at public bathing beaches.  Baltimore County also samples in larger areas of open water subject to frequent recreational use. Various chemical parameters such as temperature, salinity, and pH are also routinely measured.

Bathing beach monitoring consists of five samples taken in a pattern designed to represent the designated swimming area at the facility.  Sample runs are made every two weeks for tidal water bathing beaches and monthly at fresh water bathing beaches.

Non-regulated open areas in tidal waters typically subject to recreational uses such as boating, fishing, skiing, or wind surfing that involve only occasional full body contact and occasional accidental ingestion of water are also sampled on a bi-weekly basis.

Sampling for tidal waters is typically conducted from early April through November, weather permitting. Sampling at fresh water beaches is performed from Memorial Day through Labor Day.  Additional sampling may be initiated in response to unusual conditions or events that could negatively impact water quality and public health.

Recreational water quality standards are used to determine the relative risk of illness for swimmers. Beach closures and associated Water Contact Alerts are based on consideration of the geometric mean of results for that beach or area and any known or suspected sewage contamination. The association of sewage contamination with elevated indicator organism concentrations is particularly important because sewage carries a significant array of human pathogens, greatly increasing the possibility of contracting a water borne illness. Elevated, naturally occurring bacteria concentrations due to water fowl, marsh decomposition, or normal ground surface runoff are, in general, not considered to have as great a public health significance.

The USEPA/MDE bacteriological standard for consideration of beach closure at tidal beaches is a geometric mean of 104 MPN, Enterococci. The USEPA/MDE bacteriological standard for fresh water beaches is a geometric mean of 235 MPN, E. coli.

The results for open recreational waters are considered individually and as a geometric mean. The geometric mean beach closure standards for Enterococci and E. coli are used for comparison purposes only in conjunction with information regarding known or suspected sewage contamination to evaluate the need for a Water Contact Alert.

In cases where there is no suspected sewage overflow, there are no mandated standards for evaluation. The County, therefore, considers sampling results, other sources of possible contamination, sampling history, and environmental factors to determine the need for increased concern, investigation, or public notification regarding water quality.

This evaluation also reflects the manner in which the public uses these waters. The majority of activities, which routinely occur in these areas, seldom involve the participation of very young children or immune-compromised individuals. In addition, activities do not typically consist of constant, complete repeated immersion in, or ingestion of water. This reduces both the opportunity for exposure and pathways for bacteria to enter the body. Occasional, reduced water quality in these areas therefore poses less of a risk to the general recreational population.