NC0024112_Toxicity_20201116

Division of Water Resources
November 16, 2020
MEMORANDUM
To: Lon Snider
Water Quality Regional��Operations, WSRO
Through: Cindy A. Moore (�-7
Supervisor, Aquatic Toxicology Branch (ATB)
From: LorimarS. Henning sf
Environmental Specialist II, Aquatic Toxicology Branch (ATB)
Subject: Whole effluent toxicity test results
Thomasville -Hamby Creek WWTP
NPDES Permit # NC0024112/001
Davidson County
The aquatic toxicity test using flow -proportional composite samples of effluent discharged from
the Thomasville -Hamby Creek WWTP has been completed. Thomasville -Hamby Creek WWTP
WWTP has a permitted effluent discharge of 4.0 million gallons per day (MGD) entering Hamby
Creek (7Q10 of 0.43 CFS). Whole effluent samples were collected on November 3 and
November 5 by Mike Mickey and facility representative Misty Conder for use in a chronic
Ceriodaphnia dubia pass -fail toxicity test. The test passed. Toxicity test information follows.
Test Type 3-Brood Ceriodaphnia dubia chronic pass -fail
Test Result Pass
Test Concentrations 90%
Control Survival 100%
Control Mean Reproduction 20.9 neonates
Test Treatment Survival 100%
Treatment Mean Reproduction 23.1 neonates
First Sample pH 7.52 SU
First Sample Conductivity 546 micromhos/cm
First Sample Total Residual Chlorine 0.06 mg/L
Second Sample pH 7.40 SU
Second Sample Conductivity 366 micromhos/cm
Second Sample Total Residual Chlorine 0.05 mg/L
Test results for the above samples indicate that the effluent would not be predicted to have
water quality impacts. These samples were split and tested by Meritech, Inc. The chronic
Ceriodaphnia dubia pass/fail test run by Meritech resulted in a pass. Please contact us if you
have any questions or if further effluent toxicity monitoring is desired. We may be reached at
[phone].
Basin: Yadkin -Pee Dee
cc: Mike Mickey (WSRO)