June 20, 2006

Water quality monitoring tied to the Milltown Reservoir cleanup is underway. Key to this effort is the now-final Remedial Action Monitoring Plan (RAMP) (PDF), which is designed to keep the river and groundwater from becoming polluted during all construction activities in the Milltown reservoir area.

CFRTAC’s technical advisor Chris Brick offered this summary of the first two weeks of monitoring:

The initial drawdown of the reservoir began June 1st, about two weeks after peak runoff, and the reservoir is currently about 6.7 feet lower, fluctuating slightly with flow in the river. The level will continue to drop as flow decreases until it is drawn down about 10 feet. So far it’s gone well, and water quality has been similar to other years of spring runoff. River water quality is being monitored closely, and the results are available daily at the following website: ftp://milltown.envirocon.com/ (Drag the “Surface Water Monitoring Data” folder to your desktop and open it on your computer, not on the ftp site.)

In the first week, turbidity (the cloudiness of the water measured in units known as NTUs) nudged up to the project standard, triggering daily sampling for arsenic, copper and total suspended solids. Arsenic and sediment were both high at Turah (above the dam), but remained below warning limits below the dam.

In the second week, heavy rain kicked up both flow and turbidity in the river. Turbidity was above the standard (12 NTU) most of the week, getting as high as 29 NTU. Daily sampling for arsenic, copper and total suspended solids continued, and these parameters remained below warning limits. The highest arsenic value in the river below the dam was 6 micrograms per liter.

By June 15th, flows in the river were declining along with turbidity, which fell below the 12 NTU trigger value. Both have continued to fall for the past couple days, and arsenic, copper and total suspended sediment have also decreased. Arsenic in the river is currently at 3-4 micrograms per liter.

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