C.4.1 Runoff water preparation for water column toxicity test

column at the disposal site. The recommended procedures for water column

toxicity tests for evaluation of runoff discharges are conducted in generally the

same manner as those for discharges of material into open water as described in the

Inland Testing Manual (ITM) (USEPA/USACE 1998). The only exception is that

the toxicity test medium is prepared using the SLRP or RSLS runoff procedure.

The results of the water column toxicity tests should be interpreted considering

the effects of mixing. If the concentration of dissolved plus suspended contami-

nants, after allowance for mixing, does not exceed 0.01 of the toxic (LC50 or

EC50) concentration beyond the boundaries of the mixing zone, the discharge is

predicted not to be acutely toxic to water column organisms. If the concentration of

dissolved plus suspended contaminants, after allowance for mixing, exceeds 0.01

of the toxic concentration, the discharge is predicted to be acutely toxic to water

column organisms.

C.4.1 Runoff water preparation for water column toxicity test

The volume required for each analysis, the number of variables measured, and

the desired analytical replication will influence the total runoff sample volume

required. A 4-L cylinder is normally used for the test, and the supernatant volume

available for sample extraction will vary from approximately 500 to 1,000 mL,

depending on the sediment properties, settling times, and initial concentration of

the slurry. It may be necessary to composite several extracted sample volumes or

to use large-diameter cylinders to obtain the total required volume.

C.4.2 Apparatus

The following items are required:

a. SLRP or RSLS apparatus.

b. Several 4-L glass bottles with teflon caps.

c. Clock with second hand.

C.4.3 Test procedure

Sample collection and preparation. Runoff samples for the water column

toxicity test are collected in 4-L bottles as described in the SLRP or RSLS runoff

procedures. It may be necessary to let the samples settle and the supernatant

carefully removed so that the suspension is clear enough at the first observation

time for the organisms to be visible. The general guidance in the ITM should be

followed in performing the toxicity tests.

C10

Appendix C Test Procedures for Surface Runoff Discharges