Mandeville Monitoring

Comite field crew Jason Day and Joel Mancuso carried out monitoring at the Bayou Chinchuba and Tchefuncte Marsh assimilation wetlands. Leaf Litter biomass was collected from each forested site (M-Tmt, M-Mid, M-Ref & TM-Tmt). Dissolved oxygen, conductivity, temperature, salinity and pH were measured at all sites. TM-T discharge is off. Water nutrient and water metals samples were taken at all sites TM-Out. Water nutrients were delivered to Curtis Environmental in LaPlace, LA. Free chlorine measurements were made at the package plant that discharges into a canal that leads out to the Mandeville TM assimilation wetland. Measurements were made at the package plant discharge pipe (0.2 ppm) and where the canal meets the wetland (0.0 ppm). Vegetation percent cover estimates were done at all sites. Accretion measurements were taken at the TM-T site. The TM-Mid site was not visited due to land access issues.

Jason Day at the TM-Ref site on August 21, 2018.
Jason Day at the TM-Ref site on August 21, 2018.

St. Charles Monitoring

St. Charles Parish has been using wetlands assimilation since 2008. The wastewater treatment facility consists of a facultative oxidation pond with a chlorination and dechlorination disinfection system with an average discharge of 1.6 million-gallons-per-day. Before 2008, the treatment plant discharged into Cousin Canal, which drains into Lake Cataouatche via the Louisiana Cypress Lumber Canal. Starting in 2008, the treated municipal effluent was piped approximately 150 ft to a 1439 ha cypress-tupelo dominated forested wetland. Effluent is retained within the project boundaries by low-lying levees running along the northern, eastern, and western boundaries that prevent hydrological exchange with the surrounding landscape, except at the southern most extent of the project area where water flows out of the project area into the Louisiana Cypress Lumber Canal and then to Lake Cataouatche.

Comite Resources carried out a carbon sequestration study at the St. Charles assimilation wetlands. Changes in carbon stocks of trees and soils as well as methane and nitrous oxide emissions were measured over a one-year period and compared to baseline conditions derived from the scientific literature (see Carbon Sequestration). Methods and equations were applied from the American Carbon Registry (ACR) wetland carbon offset methodology ‘Restoration of Degraded Deltaic Wetlands of the Mississippi Delta’. The results of the study demonstrate that wetland assimilation increases wetland productivity and enhances carbon sequestration. See Lane et al. 2017 for the peer-reviewed scientific study.

Comite Resources has been carrying out wetlands assessment of the site since effluent was diverted into the wetlands in 2008. Monitoring includes measurements of tree growth (dbh & leaf) and productivity, water hydrology, soil accretion, and nutrients and metals concentrations of surface waters, soils and vegetation. These measurements are made at permanent plots located in the forest directly impacted by the effluent (termed the Discharge site), where the surface water exits the assimilation wetland (termed the Out site), and a site in between these two sites (termed the Mid site), as well as a nearby Reference site that is not impacted by the effluent for comparison (see Hunter et al. 2009b and Hunter et al. 2018). Below are monitoring reports from this site describing work carried out and preliminary data.

Location of wetland monitoring sites at the St. Charles assimilation wetlands. R = Reference site, D = Discharge site, M = Mid site, and O = Out site.

 

Hammond Monitoring

The Hammond assimilation wetlands consist of 121 ha of mostly emergent wetlands located just north of the Joyce Wildlife Management Area, which encompasses about 14,000 ha. Once effluent exits the assimilation wetlands it then flows through this much larger wetland complex. Hammond’s treatment system has a design capacity of 8 million-gallons-per-day with a three-cell aerated lagoon. A 1.2 km effluent distribution system disperses effluent along the northern edge of the assimilation wetlands.

The Joyce Wildlife Management Area used to be a thriving cypress-tupelo forested wetland (see Shaffer et al. 2015). During the past century and a half, there have been a number of significant modifications to the landscape that substantially altered the hydrology of the region (see Lane et al. 2015). Now most trees are dead due saltwater intrusion and the lack of freshwater, and the area has converted to emergent wetlands dominated by smooth cordgrass (Spartina alterniflora). The living cypress that are left are confined to the northern reaches where the addition of municipal effluent has created a freshwater buffer that counters higher salinities coming from the south. Comite Resources planted several hundred cypress seedlings directly in the path of the municipal effluent over a decade ago, and now these trees are growing very fast at 2 cm/yr in diameter (see Hillman et al. 2018).

Comite Resources has been carrying out wetlands monitoring at the Hammond assimilation wetlands since discharge began in 2006. Monitoring includes measurements of tree growth (dbh & leaf) and productivity, water hydrology, soil accretion, and nutrients and metals concentrations of surface waters, soils and vegetation. These measurements are made at permanent plots located in the area directly impacted by the effluent (termed the Discharge site, taken at the boardwalks), where the surface water exits the wetland complex (termed the Out site), and a site in between these two sites (termed the Mid site). Since the Mid site is forested and the Discharge and Out sites are emergent wetlands, there are two Reference sites, an emergent and forested, not impacted by the effluent. Below are monitoring reports from this site describing work carried out and preliminary data.

Location of wetland monitoring sites at the Hammond assimilation wetlands. D = Discharge site, M = Mid site, and O = Out site, Rf = Forested Reference site, Re = Emergent Reference Site.

CHS Monitoring

Comite Resources designed two stormwater wetlands directly north and south of CHS, Inc. bulk grain transfer terminal, which handles both grain and grain by-products. The facility transfers grain from barges to ocean going vessels and services about 2 to 3 ships per day. Because of the high volume of grain handled by the facility, grain dust and spilled grain is deposited on the site and washed into the stormwater system. To address this problem, CHS partnered with Comite Resources to construct two wetlands totaling 2.5 acres to reduce total organic carbon (TOC) from stormwater runoff. Herbaceous species were planted and also colonized the area naturally, and baldcypress seedlings were planted at a density of 200 per acre, for a total of 500 trees. Hillman et al. (2018) reported a mean diameter growth increase of 2.5 cm/yr for these seedlings, which is very high. The use of wetlands to remove pollutants from stormwater runoff has great potential as a cost- and energy efficient method of improving water quality while also providing habitat for wildlife (see Stormwater Wetlands). The CHS stormwater wetlands have many species of birds living in the wetlands along with alligators, fish and frogs. Comite Resources visits CHS stormwater wetlands quarterly to carry out stormwater wetlands assessment and environmental monitoring to assess TOC reduction efficiency, vegetation growth, and overall health and system performance. Below are monitoring reports from this site describing work carried out and preliminary data.

Imagery of the CHS facility with the stormwater wetlands, labeled as North and South ponds, located on either side of the facility.

St. Martinville Monitoring

The city of St. Martinville began discharging treated effluent from the city wastewater treatment facility to the Cypress Island Coulee wetlands in 2011. The treatment facility has a maximum design flow of 1.5 million-gallons-per-day, and consists of a 63.7 ha facultative lagoon with ultraviolet disinfection and a cascade aeration structure. The Cypress Island Coulee wetlands are located adjacent to the treatment facility and consist primarily of water tupelo, baldcypress, and swamp red maple. These wetlands have been degraded by conversion of surrounding areas to rice and crawfish ponds, and now consist of a number of shallow ‘ponds’ separated by low levees. Treated effluent is discharged at six different locations and surface water drains into the Cypress Island Coulee after flowing through the wetlands. Comite Resources has been carrying out wetlands assessment of the site since it was officially permitted in 2011. Environmental monitoring includes measurements of tree growth (dbh & leaf) and productivity, water hydrology, soil accretion, and nutrients and metals concentrations of surface waters, soils and vegetation. In order to monitor the effects of this discharge on the vegetation of the receiving wetlands, several sets of study sites (Discharge, Mid, and Out) were established, as well as three Reference sites located in nearby wetlands. Comite Resources visits these sites monthly to carry wetlands assessment and environmental monitoring. Below are monitoring reports from this site describing work carried out and preliminary data.

Results from several ongoing and completed studies of wetland assimilation systems in Louisiana indicate that they are achieving the ecological goals of enhancing water quality, stimulating vertical accretion, and increasing productivity. At low loading rates, nutrient reductions are high, often greater than 80%, due to plant uptake, denitrification, and burial. There are substantial economic and energy savings for small communities and non-toxic industrial processors. Wetland assimilation can provide an economically viable, effective and sustainable alternative to expensive conventional tertiary treatment while also providing wetland restoration in a subsiding coastal zone.

Location of wetland monitoring sites at the St. Martinville assimilation wetlands. Ref = Reference site, D = Discharge site, M = Mid site, and O = Out site.

Breaux Bridge Monitoring

The city of Breaux Bridge began discharging treated effluent into the Cypriere Perdue Swamp starting in 1954 when a city-wide sewage collection system and wastewater treatment plant were constructed.  The city uses a 3-stage oxidation pond and chlorination-dechlorination disinfection system with the capacity to treat 1.27 million-gallons-per-day prior to discharge to the wetlands. The 1470-ha swamp wetlands are dominated by very large baldcypress, water tupelo, and swamp red maple trees, as well as black willow and tallow in some disturbed areas. The wetland is hydrologically bounded to the east, north, and west by natural levees, and drains into Ruth Canal that forms the southern boundary and connects to Bayou Teche and the Vermillion River. Comite Resources has been carrying out wetlands assessment of the site since it was officially permitted in 1997. Monitoring includes measurements of tree growth (dbh & leaf) and productivity, water hydrology, soil accretion, and nutrients and metals concentrations of surface waters, soils and vegetation. These measurements are made at permanent plots located in the forest directly impacted by the effluent (termed the Discharge site), where the surface water exits the assimilation wetland (termed the Out site), and a site in between these two sites (termed the Mid site; Hunter et al. 2018). A nearby Reference site that is not impacted by the effluent is also monitored for comparison. Below are monitoring reports from this site describing work carried out and preliminary data.

The Cypriere Perdue Swamp is a healthy forested wetland that has been assimilating nutrients from treated municipal effluent for nearly six decades with no apparent negative impacts to ecosystem function or water quality. Many forested wetlands in Louisiana are in a degraded condition due to impoundment and subsidence, and outside sources of nutrients are needed to increase productivity, organic matter deposition, and subsequent accretion. Treated effluent can be a valuable source of nutrients and suspended material for degraded wetlands in coastal Louisiana.

Location of wetland monitoring sites at the Breaux Bridge assimilation wetlands, also known as the Cypriere Perdue Swamp. R = Reference site, D = Discharge site, M = Mid site, and O = Out site. The small arrows indicate discharge locations, the large arrows indicate water flow, and the dashed line delineates the boundary of the assimilation wetland. The Reference site was moved after the permit was issued because the number of discharge points increased from one to five.