Lake Lewisville Zebra Mussel Mitigation and Control
The Upper Trinity Regional Water District (UTRWD) hired Lockwood, Andrews & Newnam, Inc. (LAN) to evaluate options to mitigate the negative impacts of zebra mussels at their Lewisville Lake Raw Water Intake Structure. The project began in anticipation of zebra mussel colonization on raw water intake equipment at the lake after zebra mussel DNA was discovered in various locations throughout the lake. LAN studied conditions at the lake, researched proven strategies across the country and recommended protection strategies for the intake structure on an accelerated schedule (completing the study within 3 months) to maintain an aggressive response by UTRWD.
One main challenge of the study was that Texas did not have any known protection systems in place. LAN was able to utilize expertise company-wide with proven results from projects in the Midwest region where zebra mussels have been colonialized for over 25 years. LAN used that knowledge to evaluate strategies and develop a multi-part response to potential infestation that included chemical feed, protective coatings and cathodic protection. Design of the primary control system (chemical feed) was completed in just under 5 months in order to begin construction before the next zebra mussel spawning season. As a result LAN and UTRWD successfully bid the first construction project for zebra mussel mitigation protection in Texas and are proactively seeking to begin protection measures on other infrastructure within the UTRWD system.
At a glance
As the first response/control project in the state, coordination was required with the Texas Commission on Environmental Quality (TCEQ)
Given that the intake structure is on Lewisville Lake, extensive design and construction coordination was required with the United States Army Corps of Engineers
To compress the design schedule further, a conceptual design workshop was conducted rather than an extended 30% design phase
The control strategy included economical use of in place infrastructure, in this case a cathodic protection system
To fit all required equipment in the very limited space available, stackable chemical totes were used for chemical feed storage
The Lewisville Lake Intake Structure is jointly owned and operated by the City of Lewisville, requiring extensive design and construction coordination
The response strategies considered in the preliminary evaluation included various physical and chemical controls
To provide occupational safety with the introduction of these control chemicals, self-contained safety equipment (shower and eye wash) were included in design because construction of a potable water line was not permitted
The preliminary study also included evaluation of other UTRWD infrastructure, including water treatment plants, balancing reservoirs and transmission pipelines