United State* Office of Water Publication # EPA 833-F-94-004
Environmental Protection 4203 June 1994
Agency
EPA SUMMARIES OF STORM WATER
SPECIAL PROJECTS
Whole Effluent Toxicity of Storm Water
Discharges from an Airport
Acute Toxicity of Storm Water Discharges from BWI Airport
This storm water project was conducted during 1993 and investigated the acute toxicity of storm water discharges from
Baltimore-Washington International (BWI) Airport in Maryland. There is a US Weather Service Climatological monitoring
station to record storm events and also existing programs for storm water collection, flow analysis and chemical analysis (which
are collecting additional data for planned storm water mitigation projects at the airport) that were used for this project
The two sampling sites for this project were located at Kitten Branch which drains to the Patapsco River and Muddy
Bridge Branch which drains to Curtis Bay. During the winter months, de-icing activities at the airport discharge to both of these
locations. The Kitten Branch discharge point receives runoff from the main terminal area and the primary de-icing area while
Muddy Bridge Branch receives discharges from the commuter flight area. Four storm events were sampled. The results of the
two winter storm events are summarized below.
The first storm event sampled took place in mid-February, 1993, and included ice, snow, sleet and rain. Planes were de-
iced during the morning. A sample taken at Kitten Branch was light to medium pink showing that de-icing mixture was present.
The sample taken at Muddy Bridge Branch did not appear to have any color however, all the samples taken contained some
ethylene glycol as indicated by refractometer readings. Bioassays were started the day after the samples were taken. Peak
concentration and composite samples were tested from Kitten Branch and peak concentration samples were tested from Muddy
Bridge Branch. The two species tested included the fathead minnow and daphnid.
The second storm event sampled took place in late February, 1993, and included ice and snow with very little rain. All
de-icing took place at the primary de-icing area (Kitten Branch location). Planes were de-iced all day but more de-icing occurred
during the morning. Peak and composite samples were collected from both sites. Kitten Branch samples appeared bright pink and
refractometer readings demonstrated that the concentration of ethylene glycol was much greater in the samples from the second
storm event since there was no rain during the second storm event which could dilute the de-icing mixture. The Muddy Bridge
Branch sample did not appear to have any color and together with refractometer readings indicated there was only a small amount,
if any, ethylene glycol in the sample. Bioassays were started the day after the second storm event samples were taken. Peak and
composite samples were tested from Kitten Branch and peak samples were tested from Muddy Bridge Branch. Samples from
Kitten Branch had to be diluted because the samples caused almost instant mortality in the test organisms.
Results from both storm events showed that Kitten Branch samples were toxic and that the Muddy Branch samples were
only minimally toxic. The results also showed that samples from storm event 2 were much more toxic than samples from storm
event 1. For storm event 1, for Kitten Branch peak samples, the 48 hour LC50 (as % effluent) was 34.3% for fathead minnows
and 54.8% for Daphnids and 63.5 % for fathead minnows and 69.3% for Daphnids for composite samples. For storm
event 2, the 48 hour LC50 for Kitten Branch peak samples was 1.1% for fathead minnows and 1.7% for Daphnids and for com-
posite samples it was 1.5% for fathead minnows and 1.7% for Daphnids. The Muddy Bridge Branch peak samples for storm
events 1 and 2 and the composite samples for storm event 2 were not toxic to the fathead minnow. The 48-hour LC50 for the
Muddy Bridge Branch peak sample for storm event 1 was 50% for Daphnids.
Chemical analysis of the samples was performed by Maryland Environmental Services and the details are provided in a
final report. For more information contact Melvin H. Knott of the Maryland Department of the Environment at (410) 631-3906.
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