City announces strategy for dealing with stagnant canal

by | Oct 17, 2017 | Around Town

From City of Fredericksburg

Several concerns have surfaced over the past few months regarding the historic Rappahannock
Canal resource. City staff has been working diligently to address issues such as the lack of fresh
water entering the system, an overabundance of duckweed and other surface aquatic vegetation, and
inquiries regarding mosquito populations and the potential associated public health concerns.
Earlier this year City Public Works crews discovered a significant failure with the intake pump that
delivers water from the Rappahannock River into the canal to keep it full. After a lengthy overhaul
process at a pump repair facility, the pump was returned to the City in early October and crews
reinstalled and activated it during the week of October 9. As of today, the canal water has been
restored to normal levels.
Staff has also been monitoring dissolved oxygen levels in the water, which is important for aquatic
life, including fish that inhabit the canal. Recent tests found that oxygen levels were low; however,
the recent pumping of water into the canal, as well as ongoing efforts to repair the canal aeration
system is anticipated to improve dissolved oxygen levels.
The recent water pumping and aeration has also improved agitation of the water system and
displaced a majority of the duckweed and other aquatic vegetation from the water surfaces,
improving the appearance of the waterway. While duckweed is a common and oftentimes beneficial
aquatic plant, the high concentrations that were experienced in the canal this past year caused
surface waters to receive an inadequate amount of air and sunlight, resulting in lower dissolved
oxygen levels and impacting aquatic life, and causing an unsightly appearance. Lastly, the addition of
“fresh” water to the system also serves to dilute excess nutrients and other pollutants that may be
entering the canal through residential and general storm water runoff.
Another concern over the summer was mosquito borne diseases promulgated by mosquitoes
emanating from or near the canal. In response to citizen concerns, the City completed trapping and
testing of mosquitoes along the canal in September using a professional mosquito control company,
Clarke Environmental. Results of the testing did not show elevated mosquito populations along the
canal, nor the presence of mosquito related viruses. Despite the recent appearance of the canal,
Clarke Environmental determined that the canal is not a major contributor to mosquito populations,
and further stated that mosquitoes are more prone to grow in small containers in residential yards.
Residents are encouraged to be vigilant in their own yards and to tip, toss, and cover containers
holding standing water.
City Council has identified the canal as a valuable resource that needs to be maintained in a healthy
and attractive condition – naming it Priority # 27 (not a ranking of importance) in their recent
Visioning work last year. City Public Works staff is planning to achieve this goal by continuing their
ongoing efforts to make short term improvements, such as further repairing the aeration system,
reduction of floating vegetation and trash, and removal of fallen trees; and also continuing to
develop long term strategies and budgeting to maintain the Canal as a viable resource for future
generations. This work is likely to be in cooperation with the U.S. Army Corp of Engineers who
recently toured the Canal at staff’s request.

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