Floodgate change may save district money
GONZALES -- A proposed design change in the foundation of the Henderson Bayou floodgate is expected to provide the East Ascension drainage board a net savings of about $194,600, parish officials said.
Combined with another recent contract change to account for a parish sales tax exemption for the contractor, the project’s construction cost has fallen from $15.89 million to $15.027 million, or about $865,328, parish officials said.
The proposed foundation change comes after urging from project contractor Cajun Constructors Inc. to speed up pile installation for the floodgate, pump station and related retaining wall, fuel storage area and diversion dyke.
The plan, which is now being designed by Camp, Dresser and McKee Inc., would switch from drilled shaft piles to precast concrete piles, according to a drainage board change order.
The Henderson Bayou levee and floodgate in Galvez are designed to halt backwater flooding out of the Amite River from moving upstream into Henderson Bayou and causing flooding problems farther west and north.
Both piling systems are designed to bolster structures, including against sideways forces, according to a May 2010 Federal Highway Administration guide on drilled shafts.
With drilled shaft piles, pile holes are dug and concrete is poured inside with reinforcing material. Precast piles are driven into the ground with a pile driver.
On Feb. 6, the East Ascension Consolidated Gravity Drainage District No. 1 Board of Commissioners backed the change order and a related request for CDM to redesign the foundation based on Cajun’s recommendations.
“It’ll be a lot easier for them to install it, save some time and also be a value to us” as far as savings, Bill Roux, East Ascension drainage director, told the commissioners.
CDM did the original design for the floodgate and levee. Cajun’s requests followed the use of test piles in December.
The switch would require an increase in the number of piles from 284 to 475. The new piles would be 14 inches by 14 inches by 60 feet long.
Also, a 9-foot by 9-foot by 4-foot slab would replace drilled shafts meant to support the diversion dyke, a change order memo from Cajun states.
The changed design will save $342,415 on construction costs but the added engineering will cost an additional $147,818, resulting in the net savings of about $194,600.
The project is being paid for with a $65 million bond issue dating from 2007 and backed by the East Ascension drainage half-cent sales and 5-mill property taxes. The 40-year bonds generated about $60 million in proceeds for earmarked projects.
According to Cajun’s estimates, CDM’s redesign is expected to take six weeks.
The overall cost of the Henderson Bayou project, at $21 million, remains close to the early budget figure of $20 million, a report from Roux states.