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Monitoring Response to the Stormwater Discharge at the Proposed Pointe aux Chenes Pumping Station, Project #MX974605

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Introduction

The overall hypothesis being tested is that stormwater additions will result in higher plant diversity and biomass and higher accretion rates. This hypothesis will be tested by measuring nutrient concentrations of surface water and sediments, sediment accretion, plant cover and biomass in both the control and treatment areas. Accretion will be measured in both the control and experimental areas using feldspar markers and sediment elevation tables as appropriate for each location.

I. Background: The Barataria-Terrebonne estuary has been eroding at a rate of up to 103.6 square kilometers of marsh a year for several decades. If the current rate of loss is not slowed by the year 2050, an additional 2,550 square kilometers of coastal wetlands will be lost (Louisiana Coastal Wetlands Conservation and Restoration Task Force, 1998). One of the contributing factors to the deteriorated state of this estuary is that the Mississippi River is leveed, thereby preventing the historical spring flooding into the Barataria-Terrebonne estuary (Reed, 1995). Another important factor is the submergence rate. This estuary is sinking at a rate of one centimeter per year (Reed, 1995).
Currently, stormwater in Terrebonne Parish, Louisiana, is pumped into canals where it quickly makes its way into the recreational and shellfish growing waters of the Gulf of Mexico. An opportunity exists in the Barataria-Terrebonne estuary to use this stormwater for wetland restoration. There are 256 pumping stations in the Barataria and Terrebonne estuary and these stations have the potential to be diverted, either completely or partially, into degrading wetlands.

II. Objectives: The objectives of this project are to: (1) Determine the response of vegetation, sediment accretion, and marsh elevation of degraded coastal wetlands in the Point Aux Chenes Wildlife Management Area to this stormwater discharge and (2) Monitor the effects of stormwater discharge on wetland soil and water quality (nutrient concentrations, dissolved oxygen, and salinity).

III. Results/Outcomes: Once diverted into the marsh, it is anticipated that this stormwater will push back the intruding saline waters of the Gulf. The nutrients will stimulate growth of the emergent vegetation and the suspended particulate matter will be captured and settle out counteracting the sinking of the soil and importantly because the stormwater will take longer to reach the recreational and shellfish growing waters, bacteria and viruses will die off before reaching them. Through the activities conducted in this project, data will be collected prior to the diversion of stormwater into the marsh and after the pump has been directed into the marsh so that the degree of benefit of redirecting stormwater pump discharges can be determined.
The overall hypothesis being tested is that stormwater additions will result in higher plant diversity and biomass and higher accretion rates. This hypothesis will be tested by measuring nutrient concentrations of surface water and sediments, sediment accretion, plant cover and biomass in both the control and treatment areas. Accretion will be measured in both the control and experimental areas using feldspar markers and sediment elevation tables as appropriate for each location.

Monitoring Parameters

Sedimentation rates
- Feldspar-Short term
- SET - Long term
Hydrology
- water level recorders
Water quality
- monthly water quality samples
Sediment characteristics
- seed bank study
- mineral content
Vegetation characteristics

Gulf of Mexico Program Office
Mail Code: EPA/GMPO
Stennis Space Center, MS 39529-6000
228-688-3726
FAX: 228-688-2709


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