C.3.2 Sediment characterization

C.3.2 Sediment characterization

The following sediment characterization test should be performed in

replicates of three on the dredged material in the lysimeter prior to each rainfall

simulation run (wet and dry).

Sediment Moisture. Three replicate samples (1 to 2 g) of wet sediment are

placed in preweighed aluminum pans and oven-dried at 95 EC for 48 hr. The

pans are then removed and reweighed to determine percent water on a dry weight

basis using the formula ((wet weight dry weight) /dry weight) H 100).

C.3.3 RSLS procedure

Up to eleven 208-L (45-gal) drums or 2,290 L of sediment are required to

conduct the RSLS test. The sediment is loaded into the lysimeter one drum at a

time, mixing as the sediment is dumped. Polyethylene shovels or large spatulas

are used to mix the material as effectively as possible. Final depth of the

sediment in the lysimeter is approximately 33.0 cm. The interstitial water is

allowed to evaporate and a series of rainfall simulations are conducted while the

sediment is still anaerobic. Three 30-min storm events at 5.08 cm/hr (2 in./hr) are

applied on successive days (Skogerboe et al. 1987). Runoff rates are measured

every minute, and 4-L runoff samples are collected at 5, 15, and 25 min after

runoff begins to occur. Additional samples are collected in 250-ml polyethylene

bottles for pH, electrical conductivity and suspended solids determinations every

minute through 15 min and then every 5 min thereafter to 30 min. The 4-L

samples are combined at the end of the each day's test representing one replicate

of three successive test runs. After the three test runs are complete the lysimeter

is moved outside and covered with a ventilated, transparent top, and the sediment

is allowed to dry and oxidize over a 6-month period. After 6 months of drying,

the lysimeter is moved back into the rainfall simulation bay and the three

consecutive storm events are repeated on the now dry and oxidized sediment.

The sampling protocol is the same as for the wet sediment.

C.3.4 Characterization of runoff samples and preparation for

analysis

The 250-mL samples collected are subjected to the determination of

suspended solids, pH and electrical conductivity as described below. The

composite runoff samples are split and half are placed into appropriate

containers for contaminants of concern for analysis of total contaminants. The

other half of the samples are prefiltered, if necessary, through a 2.7-um filter and

then filtered through a 0.45-um membrane filter for metals or a 0.7-um glass

fiber filter for organics to represent the soluble fraction of contaminants.

Preservation of filtered samples should be done according to specific

requirements for each contaminant according to USEPA (1986).

The samples should be analyzed as soon as possible after extraction.

Dissolved and, if required, total concentrations of desired analytes should be

Appendix C Test Procedures for Surface Runoff Discharges