Coastal & Environmental Engineering

Alexis Bay Terrace Project  (Client: Plaquemines Parish)

“For this project, Manchac designed a terrace field in the marshes near the mouth of the Mississippi River. Terraces are earthen features constructed in shallow open water for the purpose of creating habitat, reducing wave energy, and inducing sediment retention. To construct the terraces, native material was excavated from within the project area to build the earthen features. Once the earthwork was complete and the terraces reached the design elevation, the banks were stabilized by planting of native vegetation. This strengthens the terrace and protects against wave action and currents. This project was funded through FEMA as a result of damages from Hurricane Katrina. Construction began in October 2015 but was delayed due to high river stages. The project was completed in November 2016. The first three photos below are aerial views of this project that were taken as the it neared completion. The last two photos are Google Earth images of this successful project after completion.


Aerial View - October 2016


October 2016

Aerial View - October 2016


October 2016

Aerial View - October 2016


November 2016

Google Earth Image - November 2016


November 2016

Google Earth Image - November 2016


Wetlands Reforestation

A U.S. Army Corps of Engineers (USACE) permit required reforestation along parts of Black Bayou, Bayou Francois and Saveiro Canal for dredging those waterways.  Ascension Parish retained Manchac Consulting Group, Inc. in 2009 to comply with USACE Federal Guidelines related to replanting (reforestation) of areas of previously disturbed wetlands. The affected area consists generally from the Marvin Braud Pump Station (previously McElroy Pump Station) along the Saverio Canal to Black Bayou, then from Black Bayou to Black Bayou Road and then from Marvin Braud Pump Station along Bayou Francois to Airline Highway.

The reforestation limits of the waterways were defined as commencing from the top bank of the canal/bayou and concluding at the inside edge of the spoil banks that were created from the waterway dredging project.

There are approximately 57 acres along the waterways that were planted with water oak, cow oak, hackberry, American elm, and bitter pecan species.  Work began in the planting season of Fall 2011.


Scope of Services included:

  • Attend meetings with Parish and regulatory agency personnel to include, but not limited to, USACE, Department of Agriculture & Forestry, Department of Natural Resources, Louisiana Department of Wildlife & Fisheries, U.S. Fish and Wildlife Service and the East Ascension Drainage District.
  • Prepare any necessary permit applications or otherwise documentation required by any and all regulatory agencies.
  • Collect and assemble all necessary and pertinent information from the Parish to prepare adequate bid documents.
  • Contract Management (Bid Review, contract, schedule, closeout)
  • USACE Paperwork & Documentation

CDBG Road Overlay Environmental Site Assessment

Manchac Consulting Group was retained by the City of Lake Charles to provide environmental site assessment (ESA) services for the City’s 2012 CDBG Road Overlay Projects.  ESA’s were performed in accordance to the most recent HUD ESA requirements.

Port Sulphur Governmental Building – First & Second Floor Rehabilitation and Mold Abatement

Manchac Consulting Group developed engineering plans and specifications to rehabilitate the first and second floors and abate the potential mold in the attic at the Port Sulphur Governmental Building.  The building sustained damages as a result of Hurricane Isaac, which made landfall in Plaquemines Parish on August 28, 2012, as a Category 1 hurricane.


project image

cityofblpdesmajorCity of Bossier City - LPDES Major Permit Modification for the Red River WWTP

A new permit was required for the Red River WWTP since the capacity of the plant was increased by over 50%. All permitting activities were handled by Manchac engineering staff. Since the capacity of the plant was being doubled, this consisted of obtaining a major permit modification. Engineers at Manchac also obtained a new permit for Bossier City’s NE WWTP. The NE WWTP currently discharges to the Red River through a 7-mile long force main. The new permit will allow the City to discharge to Red Chute Bayou which adjoins this WWTP saving the City thousands of dollars per year in O&M costs.

Plaquemines Parish - Cat Island Restoration

Manchac Consulting Group, Inc. provided preliminary coastal engineering design to support the permitting process for construction of the island restoration project.  This phase of work mainly involves the design of containments around the island, as well as the design of a revetment to stabilize the containment, and biological characterization of the wildlife of the island.

Several configurations were considered and evaluated for the layout of the island. Design alternatives will be evaluated with respect to cost, sustainability/resiliency, environmental benefits, and their integration as part of the overall island restoration permanent design.

The project includes four main tasks, outlined below:

  • Project Management Support – meetings, coordination, schedule, design and hydraulic engineering advisors, reporting
  • Analysis – data review, land loss analysis, alternatives analysis, calculation of currents and wave climate for ambient conditions, wind waves, and winter storms.
  • Civil Engineering Design – data review, design conceptualization, alternatives analysis, design sizing and configuration.
  • Biological Support – data review, baseline biological survey, agency correspondence & coordination.
  • Bidding / Contractor Solicitation
  • Construction Management and Resident Inspection.
  • Contract Closeout

Project Photo:


Buras Shoreline Stabilization & Restoration

Years of marsh loss and subsidence along the back levees near Joshua’s Marina in Buras, Louisiana, have compromised the integrity of these levees, which protect this coastal community against storm surge. In an effort to protect this important infrastructure, Plaquemines Parish retained Manchac Consulting group to design a solution.

The total budget for this project was $2.4M with half of the funding from CIAP and the other half from Plaquemines Parish. The CIAP funding had a requirement, which obligated that the funds be used on a living shoreline solution. In general, a living shoreline addresses erosion in lower energy situations by providing long-term protection, restoration or enhancement of vegetated shoreline habitats through strategic placement of plants, stone, sand fill and other structural or organic materials. Living shoreline treatments do not include structures that sever the natural processes & connections between uplands and aquatic areas. For CIAP, the living shoreline concept is limited to the use of artificial oyster reefs for shoreline protection.

The final design consisted of a bioengineered artificial oyster reef breakwater and earthen berm as the two major components. The artificial reef system was installed inside of the marina to protect the surrounding marsh and back levee in this relatively lower wave energy environment. An earthen berm was constructed to the north and south of the marina entrance to stabilize the remaining marsh in front on the levee. To enhance the long term stability of the berm, two engineered products were used to protect the seaward side of the berm. Both of the bank stabilization products utilized a mat-type cover to give immediate protection and are planted with native vegetation to give long term stability and enhance ecosystem services. The construction of this project was completed in November of 2014. The vegetation is already experiencing a great deal of new growth in the short time since it has been planted, and we hope to see the same production out of the artificial oyster reefs in the future.

Please see the attached video link to view the results of the project

Tangipahoa Parish - Property Improvements

A confidential client owns approximately 4,000 acres of land in south Louisiana.  Development on adjacent properties, past land use, and changes within the environment have negatively impacted the property and restricted re-growth of this once healthy cypress swamp land.

The site’s surface hydrology was modified due to the spoil banks created from dredging channels excavated during the timber harvest in the early 1900’s.  It appears that the hydrological change allows saline water to wash into the site from a nearby lake during storm events.  Studies have shown that the mean salinity level is not the main concern, but it is the high saline spikes resulting from severe drought or storm water surges that directly impacts growing trees.

Another important factor in minimizing salt damage is internal drainage and elevation.  Average elevation at the site is 1-foot NGVD.

The areas within the site that sustain the largest population of bald cypress include slightly elevated shorelines and areas along interior waterways that permit water recycling with the larger bayous meandering through the site.

Confidential Client retained Manchac Consulting Group to evaluate options for regenerating cypress growth on the property and utilizing the available acreage for:

  • Wetlands polishing for sewer wastewater treatment plant effluent discharge, and/or
  • Development of a mitigation bank

Manchac Consulting Group, Inc. met with various state, federal & local regulatory agencies (U.S. Army Corps of Engineers, and the State Agencies:  Dept. of Environmental Quality, Dept. of Natural Resources, and the Office of Coastal Protection and Restoration) to determine land use options, mitigation bank options, and wetlands assimilation options.

Manchac Consulting Group, Inc. also met with Parish and Municipal officials in the immediate area to solicit interest in utilizing the property for wetlands treatment from the local wastewater treatment plant’s effluent discharge.


Project Photo

Baton Rouge Metropolitan Airport Phase I Environmental Site Assessments

Manchac Consulting Group, Inc. was retained by the Baton Rouge Metropolitan Airport in 2010 to provide on-call Phase I Environmental Site Assessments.  This is a yearly retainer contract that is currently in its third year.  A total of 9 Phase I ESA's have been completed for the Baton Rouge Airport.

Typical services provided to the airport include water, wastewater, mold, toxins, air quality and general environmental consulting assistance. This type of work was completed for the following projects/buildings at the Baton Rouge Airport:

  • Building ASR-7 Phase I ESA
  • Cotton Harris Trailer Park Phase I ESA
  • Proposed Dow Hanger Phase I ESA
  • Mausoleum Site Phase I ESA
  • North Infield Phase I ESA
  • Proposed Loomis Tract Phase I ESA
  • Proposed Flight Standards District Office Phase I ESA
  • LA Army National Guard Readiness Center and FMS #8 Mold and Asbestos Assessment
  • Army Reserve Center Mold Assessment