How do I deal with issues of historic sediment contamination when assessing the groundwater-to-surface-water pathway?
In cases where groundwater is being discharged to surface water, you should, as a general matter, focus your groundwater environmental indicator evaluation on the question of whether or not contaminated groundwater is significantly impairing the quality of the surface water body. A positive environmental indicator determination would generally be appropriate where the groundwater is not affecting the surface water body in a way that leads it to fail basic water-quality criteria. In many cases, RCRA facilities are located near rivers or other water bodies characterized by historic sediment contamination. In such situations, the potential contribution of current groundwater discharge to sediment quality (and similarly, to the hyporrheic zone) would be beyond the scope of a groundwater environmental indicator determination. Instead, sediment quality issues would be dealt with as a part of the final remedy (or perhaps more broadly as part of an area-wide investigation).
