SAMPLING SITES
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Site Selection:
A sampling site must characterize both the water quality and
biological diversity of the stream and identify the sources and types of
pollutants affecting it. Several important factors to consider are: 1) mixing
characteristics; 2) presence of tributaries; 3) presence of potential discharge;
4) suitability for flow measurement; 5) accessibility/safety; and 6) suitability
for biological monitoring.
Information used in the site selection process is obtained from USGS 7.5 Minute Quadrangle Maps, onsite assessments, community recommendations of potential pollution sources and the MPCA. The preliminary assessment sheet used to assess a site's suitability for monitoring are included in Appendix A. All preliminary assessment sheets and recommendations will be kept on file.
The following criteria are used to select collection sites:
- Above and below known or suspected point (e.g. wastewater treatment plants) and non-point (e.g. feedlots) pollution sources.
- Above, below and at the mouth of major tributaries.
- At areas of public use for water contact recreation (e.g. swimming areas).
- At habitat areas of sensitive species (e.g. spawning areas important to trout and other cold water species).
- Away from the banks and in the main river current. A good way to accomplish
this is to sample from bridges or boats. When this is not possible, locate the sampling site next to the bank where homogeneous mixing of the water occurs, such as on the outside bend of a river.
- Variability of flow patterns caused by artificial physical structures such as dams, weirs, and wing walls must be considered in sample site location. These structures may influence the representative quality of the water.
- Where the river is accessible and sampling is safe. Steep, slippery or eroding banks or sites where landowner permission cannot be obtained should be avoided.
- Representative of the water quality of the reach being analyzed.
- Suitability for flow measurements.
- Suitability for biological measurements.
