5.4.3 Tier III - Rainfall Simulator/Lysimeter System (RSLS)

elutriates or from analysis of samples of wet, dry, and oxidized sediments using a

dilution calculation. If no standards for whole water contaminants exist, the runoff

water only requires analysis of dissolved contaminants. This will be true in most

cases.

Figure 5-3. Photo of the Simplified Laboratory Runoff Procedure (SLRP)

Apparatus

Predicted dissolved contaminant concentrations based on the results of the

SLRP can be used with applicable WQS to determine if the discharge is in

compliance with the standards after consideration of mixing. The mixing zone

evaluation is made for the contaminant that would require the greatest dilution.

Detailed procedures for conducting the SLRP water quality prediction of

runoff are provided in Appendix C.

5.4.3 Tier III - Rainfall Simulator/Lysimeter System (RSLS)

The Tier III RSLS, shown in Figure 5-4, provides a quantitative evaluation of

the effects of long-term drying and oxidation of dredged material on runoff water

quality. The RSLS procedure uses a mechanical rainfall simulator that accurately

simulates the kinetic energy and drop pattern distribution of natural rainfall. Wet

dredged material is placed in a soil lysimeter and is then subjected to rainfall

simulations at a standard rainfall intensity and duration. Runoff rates are

determined and samples are collected during the runoff period for analysis of

suspended solids, total and soluble COC. The lysimeter is then covered with a

transparent, ventilated top and moved outside to allow natural drying and

oxidation processes to occur. After 6 months of drying, the rainfall simulation is

repeated on the oxidized material. Conditions of the RSLS procedure can be

modified to site-specific conditions including precipitation intensity, duration,

vegetative cover, physical disturbance, etc. to provide realistic, accurate

assessments of potential water quality problems or effects of treatments or controls

to improve water quality.

Detailed procedures for conducting the RSLS test and prediction of runoff

quality are provided in Appendix C.

5-10

Chapter 5

Surface Runoff After Disposal Operations