Water Quality Improvement Project
Palouse River Toxics Study
Historical data from Ecology and USGS studies indicated high levels
of certain chlorinated pesticides and PCBs in Palouse River fish. The
contaminants of concern pose a risk to people that consume the fish.
However, the amount of data available was limited and dated. A fish
tissue study was conducted by Ecology in 2005 to give a better
understanding of the extent and severity of the problems.
During May through August 2005 Ecology collected fish samples from
the mainstem, north fork and south fork Palouse Rivers. Fish were caught
using an electro-backpack shocker and nets. The fish species collected
included largescale suckers, northern pike minnows, chiselmouth, carp,
and smallmouth bass. Fillets from these fish were analyzed to determine
the level of chlorinated pesticides and PCBs. In addition, Ecology
conducted a stormwater study in the city of Pullman. This study took
place during the winter of 2005-2006.
The good news is that the results of the fish tissue study indicate
that the levels of chlorinated pesticides and PCBs have declined
substantially over time. Some of the levels are now within human health
criteria and others are very low.
TMDL report detailing how the Palouse River will achieve water quality
standards for PCBs and dieldrin (the only chlorinated pesticides still
above standards) was completed and submitted to the Environmental
Protection Agency (EPA). EPA approved the TMDL on November 9, 2007.
The TMDL relies on:
- The natural decline of these chemicals over time.
- Stormwater control activities.
- Agricultural methods and best management practices that reduce
- Investigation of old landfills as a possible source.
- Limits placed the amount of these pollutants in wastewater
treatment plant's discharge.
WRIA: #34 (Palouse)
# of TMDLs:
PCBs and chlorinated pesticides: - 4
PCB and chlorinated pesticides TMDL - approved by EPA.
Toxics study - under development
Department of Ecology
4601 N Monroe Street
Spokane, WA 99205-1295