The area behind the Sampler should be at a lower level to prevent water from ponding on or around the Sampler grate. The direction of flow must be considered. Method 3 is perhaps the easiest as it can be done at any time. If this is the method used, place the level at several locations along the flow path in front of the Sampler to insure the direction remains fairly consistent. The further from the Sampler a variation in the flow direction occurs, the less effect it will have.
Worker safety is also an important consideration in selecting a suitable site near traffic.
The Sampler should be placed as far as possible from the traffic lanes-the wider the shoulder the better. The proposed site should be observed prior to installation to make certain the Sampler will not be run over. Hash-marked areas or shoulders proceeding a turn are often exposed to traffic when you may not expect them to be. While the Sampler can withstand occasional traffic without damage, it will fail if repeatedly run over . Often the grate will be the only piece that is damaged and can be replaced.