Vegetation Management

Invasive aquatic vegetation is a huge problem for us. It impedes the flow of water in our ditches, reduces storage volume during big storms, plugs culverts, chokes pumping operations and damages equipment. Invasive water weeds affect water quality, promote mosquito habitat and crowd out native plants. Massive growth and decay cycles create large nutrient pulses and leave a wake of sludge and biomass in the ditches that we have to remove in order to keep Longview from flooding. 

Integrated Approach

Improvement is our middle name!  We're always looking for innovative ways to do things. In the 90's, we introduced grass-eating carp to see if fish could do a better job than we were to keep invasive water weeds under control. When that didn't work so well, we went back to using excavators. We currently use a combination of mechanical and chemical methods to keep our heads above water. 

Our pump stations discharge directly to the Cowlitz and Columbia Rivers, and we want to do our part to stop invasive water weeds from spreading. In 2026, we are launching an aerial drone program so we can target problem areas and ditches that are hard to get to. Most recently, we teamed up with the City of Longview and Cowlitz County Noxious Weed Control and applied for grants to conduct field surveys and develop a strategic plan to help us get invasive water weeds under control.  

Lake Sacajawea

Did you know the City uses our ditches to deliver flushing water from the Cowlitz River to Lake Sacajawea? Without flushing water, the lake water will discolor, get warm and form algae blooms in the summer. The lake is a year-round treasure and we want to keep it that way!  Invasive aquatic vegetation in our ditches can spread to the lake where infestations look terrible, interfere with recreation, impact habitat and stress out the fish by restricting their movement and reducing their dissolved oxygen.  

Prevent the Spread

It will take more than just us to keep invasive aquatic plants from spreading. We use the Clean, Drain, Dry method to stop aquatic hitchhikers and we hope you do the same. Be careful about what you put in a home aquarium and don't dump water or plants from an aquarium into our ditches. We have plenty of invasives to deal with already, don't introduce new ones!