ML20210D494

Chronic Toxicity Bioassay Rept Diablo Canyon Power Plant

ML20210D494
Person / Time
Site:	Diablo Canyon
Issue date:	05/31/1992
From:	PACIFIC GAS & ELECTRIC CO.
To:
Shared Package
ML20210D491	List: ML20210D488 ML20210D494
References
NUDOCS 9206160066
Download: ML20210D494 (4)

Text

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.1 PG&E Letter No. DCL-92130--  ;

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CHRONIC TOXICITY BIOASSAY REPORT -1 j

DIABLO CANYON POWER PLANT.

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-. PACIFIC GAS &~ ELECTRIC COMPANY-MAY 1992-

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9206160066 920602 PDR ADOCK 05000331- '1 P: PDR --

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PG&E Letter No. DCL-92-130 CHRONIC TOXICITY BIOASSAY REPORT Diablo Canyon Power Plant NPDES No. CA0003751 -

Introduction in accordance with the 1990 California Ocean Plan (Ocean Plan), PG&E conducted chronic toxicity testing during 1991 for Diablo Canyon Power Plant (DCPP). Tho_.

purpose of this testing was tc determino compliance with the Ocean Plan chronic toxicity objectivo of no chronic toxicity (TUc = 1) at the edge of the zone of initial dilution. An additional objective was to determine the most sensitive test species so that future chronic toxicity testing could be reduced from testing three species to testing one species. Three test species chosen from the stato approved list were tested. Test species included a fish, an aquatic plant, and an invertebrate.

Methods The sensitive life stages of throo test species, red abalono (Hallotis rufoscens),

giant kelp 'Macroevstis ovrifera), and silversides (Menidia bervilina) were selected for screening. Red abalone chronic tests were conducted at the Diablo Canyon Biological Laboratory, while the giant kelp and silversides tests were conducted at the ERC B!oassay Laboratory in San Diego. All 1991 screening tests were conducted with 24-hour composite offluent samples collected from the point of discharge. The protocols approved by the State Water Resources Control Board were followed in the conduct of all chronic bloassays at the two laboratories.

Dilution water controls, reference toxicant tests, and rigorous acceptance criteria, as specified in the protocols, ensured dilution water quality and comparable

! laboratory techniques. Test results were subjected to statistical analyses as specified in the protocols.

Since water samples were collected at the point of discharge rather than at the l

edge of the zone of initial dilution, an effluoret toxicity. limit was calculated using the following formula from Chapter IV, Sectica A, of the 1990 California Ocean Plan:

l Ce = Co + Dm (Co - Cs) 1 where Ce = the effluent toxicity limit at the point of discharge Co =. the toxicity limit at the edge of the zone of initial dilution (1)

Dm = the minimum probable dilution Cs = background toxicity (= 0 for DCPP)

DCPP Dm = 4.11, Ce = 5.11 5703S/85K '

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The toxicity of water samples tested in chronic toxicity bloassays was calculated

- using the No Observed FJfect Level (NOEL). (The NOEL is the highest test y concentration of offhtant in percent that gives results not significantly different i from the control resuits.) Once the NOEL was dotarmined, the sample toxicity  !

(TUc) was calculated by dividing 100 by the NOEL (TUc = 100/ NOEL). Toxicity values below tt's effluent ioxicity'limit (Ce) aio in compliance with the chronic toxicity objective of the Ocean Plan.

Results Results of the DCPP chronic toxicity bioassays during 1991 are summarized in Table 1. Of the three positive red abalone test results, only one was above the 1 calculated effluent limit and subsequent test results were below the calculated

- effluent limit. No toxicity was detected in the fourth red abalone test not in any of the tests of the other two test species.

j Two end points were measured for the giant kelp and silversides tosts. The two end points measured for the giant kelp were percent germination and germ tube length, whereas the two end points measured for the silversides were larval growth rate and percent survival. Since tlie results w3re the same (TUc = 1) for each and point and each quarterly test, only the one value for each species is listed in Table 1.

Reports on individual chronic t icity bloassays, including all original data and statistical analpes, are avail 0ble upon iequest.

Conclusions and Recommendations

, Since omy one test result was above the calculated effluent limitation, PG&E did not detect consistent chronic toxicity at the edge of the zone of initial dilution.

l Red abalone was determined to be the most desirable test species for use in chronic toxicity testing at DCPP for the following reasons:

1. Of the three chronic toxicity test protocols, only the red abalone larval bioassays indicated chronic toxicity during the 1991 tests.

2. Red abalone juveniles have historically been the test species for acute toxicity tests at DCPP.

3. The red abalone is important in sport and commercial fisheries, and it is present in the DCPP receiving waters.

For these reasons, PG&E recommends that the red abalone larval _ development assay be adopted as the DCPP chronic toxicity test protocol.

5703Si85K - . .

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• TABLE 1 e 1991 CHRONIC TOXICITY TEST.RESULTS DIABLO CANYON POWER PLANT i .

i- Calendar 1 Toxicity

• Soecies Tested Quarter (TUcl 1

j Red- Abalone i

1st Quarter 10.06' j 2nd Quarter. 3.0'  ;'

3rd Quarter 3.0 .

{ 4th Quarter 1.0 . ,

i j Giant Kelp J

'1st Quarter: -:1.0 f_ 2nd Quarter 1.0 -

i i 3rd Quarter 1.0 4th Quarter 1.0

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Silversides

'1st Quarter - 1.0

' 2nd Quarter; 1.0 _

3rd Quarteri 1.0 6 4th Quarteri 1.0 L

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' Effluent Toxicity Limit (Ce) = 5.11 -

h 6 Indicates chronic toxicity._at the edge of the zono of initial dilution._ ,

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