Board approves canal closure plan for Lakeside

A variety of factors including the height of water at a gauge and weather forecasts will determine when officials close the Walnut Canal Barge Gate in Lakeside Subdivision to reduce flooding in the subdivision.
The St. Mary Parish Consolidated Gravity Drainage District 2 board approved an operational plan Monday for the Walnut Canal Barge Gate in Lakeside Subdivision at their monthly meeting. The gate is located at the canal’s intersection with Lake Palourde in Morgan City.
Before Monday, no formal operations plan for opening and closing the barge gate was in place.
The issue is a touchy one in Lakeside, where using the barge as a flood control measure blocks access to Lake Palourde.
The drainage district paid T. Baker Smith LLC $16,000 to analyze the existing topography and current drainage system of the subdivision to determine a water level in Walnut Canal, said Drainage District 2 Treasurer Jean Paul Bourg.
According to the analysis, the overall objective is to reduce flooding in the eastern subdivision of Lakeside by establishing an elevation at which the gate should be closed and reopened. The analysis was completed in September 2015.
The report indicates residents experience flooding caused by high water levels in Walnut Canal, local rain-fall or a combination of both.
The subdivision drains by gravity via subsurface drain pipes into Walnut Canal and then into Lake Palourde.
At the north end of the canal is a barge gate which, if closed, can prevent flooding due to high levels in Lake Palourde.
It may also restrict access to the lake for some residents. But if the barge is not closed and the water gets too high, the pipes drain poorly and flood streets and yards.
Lakeside residents attending the meeting were concerned that trash in the drainage pipes contribute to flooding and restricted flow of water.
Based on the findings, T. Baker Smith confirmed that changing the elevation at which the barge gate is opened or closed will not prevent flooding in the subdivision.
Therefore, the operational plan is to minimize the severity and duration of exposure to flooding.
In addition, the analysis revealed that the weir is probably too small for a storm event greater than the one-year recurrence interval.
Officials typically close the barge gate when the water gauge at the canal reaches around 1.75 feet high.
Other factors T. Baker Smith recommended the drainage district consider when deciding whether to close the gate include:
—Lower Atchafalaya River forecast at Morgan City.
—Current weather fore-cast.
—Estimated time between closures. Opening and closing the barge is an operational expense for the district and should be considered as part of the decision-making process.
—Availability of resources for closing the gate. A diver is required for inspecting sill and making sure the closed barge is properly sealed.
After the barge closes, the water level in Lake Palourde should reach a minimum of 1.7 feet before determining whether to re-open the barge.
Also, the Atchafalaya River forecast should indicate a downward trend with an estimated rainfall for five days to be less than 0.5 inches of cumulative rainfall when deciding to reopen.
In recent circumstances due to weather, Lakeside residents were not told that the barge would be closing.
Those attending the meeting stated that in the past, residents would receive a notice from the district stating plans to close the barge.
Drainage District 2 Chairman Lee Dragna said that if it’s possible, he would make an effort to get a 24-hour notice out to residents. However, it depends on the nature of the circumstances at the time.
Bourg also stated the district would make an effort to contact residents about barge closures.
The following short-term improvements can be implemented more quickly and require less money than long-term projects:
—Inspection and cleaning of existing subsurface system. The existing system has a lot of sediment built up in the pipes and at the junctions.
—Increase capacity of existing overflow weir at a cost of $62,360. Improvements to increase capacity, in addition to increasing the range of elevations the crest can be, should be evaluated.
—Localized plumbing totals $144,407 for one pump. Installation of localized pumping could benefit some lower areas by isolating the outfall pipe from the canal with a submersible pump and gate.
The short term suggestions do not fix all drainage problems in the subdivision, but it will help the current system function more efficiently until long-term improvements are implemented.
Options for long-term improvements are:
—Localized pumping, which costs $935,160 for four pumps