Details:

Creators:
Griffin, D. M.
Corporate Creators:
Louisiana Transportation Research Center
Corporate Contributors:
Louisiana. Dept. of Transportation and Development
Subject/TRT Terms:
[+]
Bridges--Drainage Systems Drainage Drainage Basins Drainage Structures Measurement Runoff Runoff--Louisiana--Shreveport Urban Runoff--Management Water--Pollution--Measurement Water Pollution Water Quality Management--Louisiana--Shreveport.
Publication/ Report Number:
FHWA/LA.09/447
Resource Type:
Tech Report
Geographical Coverage:
Louisiana
Edition:
Final report; May 2003-Aug. 2009.
Corporate Publisher:
Louisiana Transportation Research Center
Abstract:
The Cross Lake Bridge in Shreveport, Louisiana, spans Cross Lake that serves as the city’s water supply. Concern

about accidents on the bridge contaminating the lake prompted the Louisiana Department of Transportation and

Development (LADOTD) to construct a closed drainage system on the bridge to convey precipitation falling on the

bridge deck to a concrete lined holding pond on the east side of the lake. Once there, bridge runoff is tested for oil

and grease, pH, and lead before discharge to 12-mile bayou.

This report describes the methodology and results of two studies dealing with runoff from the Cross Lake Bridge.

The first examined the degree to which repairs to the Cross Lake Bridge’s closed drainage system were successful

in capturing runoff from the bridge. An earlier study found that, because of leakage, only about one half of the

precipitation falling on the bridge actually ended up in the holding pond. This is substantially less than would be

expected from a catchment that is essentially impervious. To test the success of repairs to the drainage system,

volume balances for 22 precipitation events were conducted by comparing the rainfall on the bridge to the

subsequent flow into the pond. The ratio of the volume of runoff to the volume of precipitation was found to

average 0.86, which when compared to values from the previous study as well as published values, suggested a

successful repair of the drainage system.

The second study examined the use of the Microtox toxicity analysis system manufactured by Azur Environmental

for use as a screening tool to assess toxicity of the pond contents. Microtox protocols rely on measurement of light

output from a specific strain of luminescent bacteria. Toxicity is indicated when light output from the bacteria

decreases. Tests can be run in time periods ranging from 5 to 30 minutes. The standard endpoint of the tests occurs

once light output has dropped 50 percent and is termed the EC50. Samples from the water column and sediment

were collected and analyzed for toxicity using the basic test (liquid) and the basic solid phase test (sediment).


Format:
PDF
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:58992489ef139e97002df2d8fdc3158e75acf9b3a451954221002ab5b2eab555
Download URL:
https://rosap.ntl.bts.gov/view/dot/16955/dot_16955_DS1.pdf
File Type:

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