Thursday - July 31, 2014

Channel work near the River Intake Pump Station Stirs up Sediment

Channelization work on the river bank

The river intake pump station (RIPS) contractor started excavating on the Clackamas River bank near the RIPS last week, as required by the Water Partnership’s environmental permits. Environmental agencies required this channelization work as part of the project to make it easier for fish to safely travel past the new intake structure. This week, excavation occurred in soft soils, causing some sediments to mix with river water, creating a visible, muddy plume. The visible sediment is similar to that caused by a winter rainstorm that washes sediment into the entire river. The difference is this sediment is confined to the area downstream from the channelization work, making it appear darker than surrounding water and more visible.

All erosion and sediment control measures are in place as required by the 401 Water Quality Certification conditions of the US Army Corps of Engineers permit, including turbidity curtains and sand bags. Per permit requirements, the contractor has been taking samples upstream and downstream of the site, measuring turbidity, or muddiness, with a monitor. All measurements to date have been within the allowable limits and in full compliance with the permit. Future excavations will continue for about a month, with the visible sedimentation likely to continue for another week. Work will then move into firmer soils and rock that are less likely to result in visible sedimentation.

If you have any questions, please call the project hotline on 503-697-6502 or contact us.