Direction of water flow through the facility was determined oneach sampling date. Flow direction was determined using a floatattached by a thread to a compass. The float was placed in the waterand allowed to be carried by the current until the thread was taut.The direction on the compass indicated by the thread was recordedat each of the three sampling points, and then compared againsta map of the facility to ensure an accurate determination of flowdirection and which point was “upstream” and which was “down-stream” for that sampling date. “Upstream” was water that had notentered the facility, or inflow, while “downstream” was water thathad passed through the facility, or outflow. Flow speed was mea-sured at each sampling point using a Model 2100 Current VelocityMeter (Swoffer Instruments Inc., Seattle, Washington).