Levels of Bolero and Abolish (thiobencarb) have hit record levels in the Colusa Basin Drain potentially impacting water quality levels for the City of Sacramento and others who take drinking water from the Sacramento River.
On May 24, the thiobencarb monitoring results reached 11.0 parts per billion (ppb) at the Colusa Basin Drain (CBD) site located in the Colusa National Wildlife Refuge. Downstream at the CBD site close to Knight’s Landing, the levels were 3.2 ppb. These levels are higher than we have observed at any point during the drought, and since the California Rice Commission took over management in 2003. All other monitoring locations have reported non-detects for the season. The thiobencarb performance goal in all rice drains is 1.5 ppb.
We ask growers and applicators to closely follow all of the thiobencarb permit requirements. If you see a violation, please call your County Agricultural Commissioner immediately.
The CRC will again increase monitoring to work with to identify the source of the exceedances. As required, we have also notified the cities of our monitoring results.
We continue to communicate regularly with the County Agricultural Commissioners and the Department of Pesticide Regulation to ensure they have the latest monitoring results, and understand the support of the industry for full use of their regulatory authority – including removing the use of thiobencarb from a grower’s permit.
We are greatly concerned that these exceedances will have a negative impact on water quality at the City intakes. The continued use of this material in the areas that drain into the Colusa Basin Drain (Colusa and Glenn Counties) and for the industry as a whole are in serious doubt with these ongoing violations.
– Tim Johnson