The largest wetland restoration project in the state of Texas is a big step closer to completion. Three interior channels are receiving finishing touches that will link the shallow waters of the 6,800 acre Bahia Grande with the nearby dry basins of Little Laguna Madre and Laguna Larga. The three basins are just north of Highway 48 between Brownsville and Port Isabel and together total nearly 10,000 acres.
Water has slowly been flowing into the long dry Bahia Grande basin since a pilot channel was dug in July of 2005. The pilot channel linking the Brownsville ship channel with Bahia Grande is only 15 feet wide at the base and runs beneath Highway 48. A permanent restoration will require a channel ten times wider and several feet deeper to allow for substantial water exchange.
The recovering estuary had been a dust bowl since being cut off from the Laguna Madre in the early 1930's when the ship channel was dug linking the Port of Brownsville to the Gulf of Mexico. Dredge material or spoil from channel construction was deposited along the banks and blocked the estuary from receiving water from the bay and Gulf. The isolation was completed with the construction of State Highway 48 between Brownsville and Port Isabel.
After years spent garnering funding and clearing titles, 21,000 acres of land known as the Bahia Grande Tract was finally purchased by the Untied States Fish and Wildlife Service in 2000 and became part of Laguna Atascosa National Wildlife Refuge. Nearly half that acreage was historic wetland and targeted for restoration.
Since the pilot channel was opened eight months ago, Bahia Grande has become nearly 90 percent filled with a sheet of water ranging in depth from a few inches to a couple of feet. The water enters on high tides thru the narrow pilot channel and gradually flows across the basin, but the depth and coverage varies depending on tides and wind direction. The adjoining basins remain isolated and have yet to receive any water from Bahia Grande.
Sonny Perez, Assistant Refuge Manager, at Laguna Atascosa National Wildlife Refuge, is supervising the construction work on the interior channels, and he anticipates water to be flowing thru them by summer. "The Laguna Larga which is approximately 1,700 acres and little Laguna Madre which is approximately 1,300 acres are still cut off from a permanent water flow, and that is what these channels will do is connect with Bahia Grande which connects to the Brownsville Ship Channel. Right now plugs have been left on both ends of the channels, but we are in the process of doing the final specifications before opening them up," Perez said. "We are hoping by summer to be able to come in and remove these plugs. We will have water flowing into the entire system, and then we will be closer to a complete restoration effort."
Perez explained that a cooperative effort between Foremsot Paving, the contractor widening Highway 48, and the refuge enabled the interior channels to be dug at a tremendous savings to all. Foremsot Paving needed fill for the expansion of the highway, and the refuge needed channels dug linking the nearby basins.
"They have helped us by bringing in their equipment and providing their services, and helping with the rough excavation, which in turn provided them fill dirt taken from channels they dug," Perez said. "It has saved on the construction of Highway 48, and it has saved on the construction of these channels. When we first discussed this with the contractor, they said they needed approximately 110,000 to 112,000 cubic years of fill for the highway expansion, and we needed to have about the same amount removed for our channels. It was perfect timing. The in kind services that the contractor has provided are in excess of $200,000."
Now that rough excavation is nearing completion, Perez is overseeing final planning for the exact dimensions of the finished channels. When the channels are refined this summer and water begins to flow into the dry basins it will bring the system much nearer complete restoration. What is needed to fully restore the wetland is a larger channel linking the entire system to the Brownsville Ship channel.
The Texas Department of Transportation is constructing a bridge over Highway 48 that will accommodate the 150 foot wide main channel that is planned. However, the cost of constructing the channel is estimated at 1.4 million dollars. Efforts are underway to secure the needed funds thru a variety of sources including the federal government and private organizations.
Laguna Atascosa is partnering with local universities to monitor the ongoing recovery of Bahia Grande. Dr. David Hicks, professor of estuarine ecology at the University of Texas at Brownsville, has been working with his students sampling the sediment and salty waters of Bahia Grande. "What we are seeing so far suggest that this system will rebound under the right conditions," said Hicks. "We are going to see it play out, step by step."
Several species of marine worms and fish have already colonized Bahia Grande, but for complete restoration increased water exchange thru a bigger channel is critical "The salinity is very, very high," said Hicks. The salinity right now is about 65 parts per 1,000. Full strength sea water is about 35 or 36 parts. Generally the Laguna Madre when you are in the area of the populated part of South Padre Island is around 36 to 37. When you move further north and you get away from the passes it can be in the 50's."
"The current salinity in Bahia Grande will not kill fish yet, but once it gets to 80 and 90 you are talking about real trouble," Hicks said. "Every month we have been monitoring since September it has been going up. Right now, this flooding of Bahia Grande is acting as a dust abatement project, but for it to flourish I think we are going to have to see that bigger channel."
The Texas Department of Transportation, Cameron County, Brownsville Navigation District, United States Fish and Wildlife Service and others are all cooperating to achieve the restoration. "This is something that never could be completed by just one agency or one entity," Perez said. "It takes everyone's involvement, and it is definitely going to be a tremendous boon for our local environment."
Refuge personnel are currently conducting a comprehensive conservation planning process which will determine public usage at Bahia Grande. Fishing, kayaking, hiking, bicycle access, and wildlife photography are all being considered. A series of public meetings will be scheduled within the next 60 days to solicit public input.
Copyright 2007 Richard Moore