Constitution Park

DURATION: October 2016 - February 2017

STATUS: completed

RIVERBANK LOCATION: In Constitution Park upstream of the Main Street Bridge and adjacent to the Dominion Pavilion and Love sculpture

RIVERBANK LENGTH: 500 feet

ESTIMATED MERCURY INPUT FROM ERODING BANKS: 12.8%

OUTCOME:

Mercury levels in sediment immediately adjacent to the riverbank began to decline within a year after completion and remailn similar to reach-wide average concentrations. A program is underway to control knotweed plants at this location. Efforts have included a series of targeted herbicide applications and physical removal. The lack of established vegetation at this location has made the riverbank more susceptible to erosion during flooding events. In 2019, maintenance activities included placing planting substrate, native live stakes and plant plugs.

Monitoring Data

For Phase I of this work, samples were collected at the remediated Constitution Park riverbank and analyzed in a laboratory. Based on the laboratory results:

Mercury levels have decreased in the sediment immediately adjacent to the remediated bank.
Before remediation, upstream sediment with elevated mercury levels had deposited on this riverbank. Now, after remediation, these deposits have been replaced with cleaner sediment from upstream areas.
Although immediately after the remediation mercury levels in the water between the grains of sediment (otherwise known as pore water) slightly increased, these mercury levels have decreased to below baseline levels.