The Effectiveness of Culvert Removal on Improving Water Quality Parameters in Carpenter Creek Estuary

Anthropogenic alterations to streams and estuaries have negative impacts on salmonid species in the Puget Sound region. Many estuaries have been dramatically altered from their natural state by the installation of undersized culverts and the degradation of riparian habitat. As part of the Washington Salmon Recovery Program, restoration of undersized culvert with bridge replacement are used to reconnect aquatic corridors and restore salmon spawning habitat. The Carpenter Creek estuary system, in the midst of Kingston’s Urban Growth Area, provides more than 30 acres of habitat that is currently in a state of recovery after estuary restoration in 2011. The monitoring program of the Carpenter Creek Estuary Restoration Project, lead by Stillwaters Environmental Center, has collected pre-restoration baseline data (2005-2011) to determine whether the restoration actions are effective in improving estuary habitat and function. This project reports on water quality data that were recorded post-restoration (2012-2015) from Carpenter Creek, the adjacent salt marsh, and estuary. A handheld multiparameter multiprobe system (YSI 556) was used to measure pH, salinity, dissolved oxygen concentration, dissolved oxygen percent saturation, total dissolved solids, and temperature. Of the parameters analyzed, significant differences existed in dissolved oxygen before and after culvert removal at each monitoring site (P = 0.04). This suggests that culvert removal and restoration of the natural hydrology in small streams raise the concentration and percent saturation of dissolved oxygen throughout an estuary. The increase in dissolved oxygen is most likely attributed to the movement of water through the system and presumably in an increase in photosynthetic organisms. Current and future studies are evaluating salmon presence and riparian vegetation. While the post-bridge water quality monitoring is still in its infancy, these early attributes may benefit salmonid species in estuarine systems of the Puget Sound