Test Results

Current Water Testing Results

Test results are provided by Fredericktowne Labs  historically from Memorial Day to Labor Day. Water test samples are collected in the evenings from Nightingale Beach, and the results are posted when provided from the lab the following day (i.e., the results from samples taken the evening of August 28 are posted on August 29).

LLA posts testing results Monday through Friday. Test results, including weekend test results, can also be found on Facebook at Friends of the Lake • Lake Linganore at Eaglehead

Test Results

Today’s results (posted September 3, tested September 1):
E.coli: 21 MPN/100 ml
Phycocyanin: 13 ug/L

What do results include and what do the numbers mean?

  • E. coli: 235 MPN/100ml is EPA’s / MDE’s Beach Action Value (BAV). Recreators in waters with E. coli exceeding the BAV, risk illness (at a rate exceeding 1 in 28 people).
  • PC (phycocyanin): 90 ug/L to 100 ug/L or higher indicates an elevated cyanobacteria (blue-green algae) population and signals the need for further testing to determine whether toxin-producing cyanobacteria and toxins are present.
  • E. coli concentrations can “spike” after it rains. So, as long as it doesn’t rain, you can use the prior day E. coli concentration to make decisions about today. Lake Linganore is no exception to Maryland Department of the Environment’s general advice that “…you should avoid swimming in natural waters within 48 hours of a heavy rain event…”.

For more information, see the FAQs below.


Why test for E. coli?
E. coli is an accepted indicator of the possible presence of bacteria or viruses in water which could cause illness. The test used for E. coli is far less expensive and more reliable than other tests. Data can be used to correlate to precipitation data, identify / remedy sources and keep the Linganore community better apprised of water quality.

What is E. coli?
E. coli or Escherichia coli is a type of bacteria commonly found in the intestines and wastes of healthy warm-blooded animals (humans included). There are more than 100 different strains of E. coli, and most are harmless. E. coli O157:H7 is one strain of E. coli (usually associated with cattle, but has found in the intestines of deer, goats and sheep) that can cause illness.

How is E. coli data reported?
Laboratories normally present testing results in units of most probable number (MPN) of bacteria colony-forming units (CFU) per 100 milliliters.

Where does E. coli in the lake come from?
The primary source of E. coli in Lake Linganore is believed to be agricultural storm water runoff (e.g., manure) from farms in the 88 square miles draining into Lake Linganore. Higher levels can be expected during or after rainfall events. Suspended sediments and algae are believed to prolong the survivability of E. coli in lake water.

When and where does sampling for E. coli take place at the lake?
The lake water is sampled daily at Nightingale Beach during the summer season (June 1, 2014 through August 31, 2014). Results are available to the community within 1 day of sampling. Because the reported results are not “real-time” and conditions vary throughout the lake, residents should be aware that the results may not be representative of the water quality actually encountered.

What is an acceptable level of E. coli?
Maryland’s public beach standards are an unenforceable point of reference for Linganore’s private beaches. Maryland regulations establish for public “designated bathing beaches” what it believes is an acceptable average (geometric mean) E coli concentration for “Frequent Full Body Contact Recreation” of 126 MPN / 100 milliliters. Also, based on statistical analysis of the daily E. coli measurements taken June 1, 2013 to August 31, 2013, Maryland regulations indicate that no single sample should exceed 459 MPN / 100 milliliters (based on the variability of E. coli concentrations in Lake Linganore).

What are E. coli levels at Lake Linganore?
Based on daily E. coli sampling of Lake Linganore during June 1, 2013 through August 31, 2013, the geometric mean E. coli concentration of Lake Linganore during the summer season is 39 MPN / 100 milliliters, well below Maryland’s mean standard of 126 MPN / 100 milliliters. There were 12 days during the summer season when E. coli levels spiked above 459 MPN / 100 milliliters daily maximum, temporary exceedances that were associated with significant (>0.4-inch over 24-hours) precipitation events.

Should I be concerned about swimming at Lake Linganore because of E. coli?
Lake Linganore has been a drinking water reservoir and recreational area for 40 years. During this time no known serious illness or injury due to E. coli exposure has been documented. Over the years, significant improvements have been made to County agricultural land and waste management practices to increase surface water quality. Residents have used and continue to use the private lake at their own risk. As with any lake, residents can reduce risks of contracting waterborne illnesses by not swallowing lake water and minimizing contact after rainfall events, during periods of excessive algae or siltation or when E. coli levels are higher than normal.

What is Phycocyanin & Why Field Scan Water Samples for it?
Phycocyanin (PC) is a pigment-protein complex found in cyanobacteria (also called blue-green algae). Because it fluoresces at certain wavelengths, PC can be conveniently and cost effectively semi-quantitatively measured in real time with field instrumentation (especially if sampling personnel are already present sampling for E. coli). PC is a surrogate / indictor for the possible presence of cyanobacteria. Cyanobacteria are of interest because they can produce toxins that may be irritating or hazardous to recreational users and pets. Microcystis, one of many types of cyanobacteria, was found in a Lake Linganore by Hood College, Center for Coastal and Watershed Studies during a 2013 algae survey. Planktothrix, another cyanobacteria was discovered in Lake Anita Louise in the winter of 2015-2016. Because field testing for PC is semi-quantitative screening method, further quantitative testing for cyanobacteria / toxins occurs if warranted by elevated or rapidly rising PC field readings. Blue-green algae like Microcystis did not predominate in bi-weekly Lake Linganore plankton surveys during May-July 2006 when lake water PC ranged from single digit to ~100 ug/L. Therefore, blue-green algae at Lake Linganore become a greater concern when PC readings rise rapidly and are well in excess of 100 ug/L . Should this occur, Maryland Department of the Environment (MDE) may conduct additional testing.