AI 44765 - Bayou Trepagnier

  •   Agency Interest Number     44765
  •  Location                            Norco
  •  LDEQ Contact                    John Halk


Site Background and Activities

Bayou Trepagnier is located east of the lower guide levee north of Airline Highway (U.S. 61) near Norco. The bayou extends north from the Hurricane Protection Levee approximately 15,500 feet to its confluence with Bayou LaBranche. The bayou received discharges of wastewater from petroleum refinery operations from the 1930’s to 1995. The site was split into two identifiable units – Operable Unit 1 (OU1) and Operable Unit 2 (OU2). OU1 is the upper reach of the bayou and extends approximately 5,500 feet in length. OU2 is the middle and lower reach of the bayou that comprises approximately 10,000 feet in length.

The New Orleans Refining Company (NORCO) facility was located on US Highway 61. The NORCO refining facility began operating in 1920. NORCO discharged wastewater and storm water into Bayou Trepagnier from 1920 until 1929, when Shell Petroleum Corporation (Shell) purchased the facility and began its operation. In 1930 the USACE constructed the Bonnet Carre’ Spillway. The Spillway’s lower guide levee eliminated the upper portion of Bayou Trepagnier. Shell, like its predecessor also discharged wastewater and storm water into Bayou Trepagnier. In 1951 the Louisiana Department of Public Works dredged Bayou Trepagnier. The dredged sediments were placed in spoils banks, primarily along the west side of the Bayou. The width of the Bayou varies from approximately 25 to 60 feet, being generally narrower in the upper reach and wider in portions of the lower reach. The refinery ceased discharge into the Bayou Trepagnier in 1995. Motiva Enterprises, LLC (Motiva) has owned and operated the facility since 1998. 

Previous investigations and risk assessments conducted at Bayou Trepagnier identified several constituents of concern (COCs). These studies found concentrations of several COCs above typical background levels (e.g., lead, chromium, zinc, and individual polycyclic aromatic hydrocarbons [PAHs]) in the sediments and surrounding soils. 
In response to public concerns and a growing need to address the environmental issues of Bayou Trepagnier, the Bayou Trepagnier Work Group (BTWG) was formed in 2000. The BTWG comprises federal, state, Motiva LLC, and non-governmental environmental organization representatives. 
Several key elements for the remedial and natural resource restoration were established by the Bayou Trepagnier Work Group (BTWG). 
·         Division of remedial work in Bayou Trepagnier by dividing the area into Operable Unit (OU1) and Operable Unit 2 (OU2);
·         Complete a Remedial Action in OU1 to reduce potential exposure risk due to contaminated sediments;
·         Construct a Clean Corridor in OU1 to allow for the potential future conveyance of fresh water to the wetland ecosystem;
·         Complete an updated Human Health and Ecological Risk Assessment for OU2 and portions of OU1 not included in the Operable Unit 1 Remedial Action; and
·         Complete a NRDA Damage Assessment and Restoration Plan (DARP) for Bayou Trepagnier incorporating the necessary elements and supporting documents for wetland restoration
Many work activities have been completed in OU1 and OU2. A LDEQ Decision Document for OU1 was issued in February 2007 to address corrective action in OU1 and address further investigation and risk analysis in OU2. 
For OU1, a Remedial Design was completed followed by a Pilot Study in June 2010 to test various stabilization and capping procedures. Remedial action in OU1 will stabilize and cap the sediments in the bayou from the Hurricane Protection Levee northward for about 5,500 feet. As part of this remedial action, complete removal of sediment and spoil bank will be done in order to allow for a future 800 foot-wide clean corridor for conveyance of freshwater into the surrounding swamp land. The cut into Engineers Canal will be filled in. 
For OU2, a RECAP Investigation was completed that analyzed sediments, spoil bank, surrounding soils, and biota and evaluated risks to human health and the ecosystem. Results of the RECAP Investigation indicated that no unacceptable risks to human health or the ecological system due to levels of contaminants present in OU2 and that no further action is warranted for the sediments, dredge spoils, and adjacent soils in OU2 as well as all other OU1 media (i.e. dredge spoils and adjacent wetland soils outside of the Clean Corridor) not included in the OU1 Remedial Action. A Decision Document was issued in October 2010.
A Natural Resource Damages Assessment (NRDA) process is also occurring for the site. Motiva is working with the NRDA trustees to review data necessary to complete the DARP and determine the amount and manner of compensation for natural resource damages.
Current Status


The Remedial Project Plan and associated sub-plans were reviewed by LDEQ and revised as needed to prepare for the remedial action of OU1.  Final approval of the Remedial Project Plan was given by LDEQ in February 2011.  Necessary permits and access approvals were obtained by Motiva for equipment laydown and access to the staging areas.  The OU1 Remedial Action commenced field operations March 23, 2011 with the collection of soil borrow material from the Bonnet Carre’ spillway. Field office trailers and construction equipment were moved on-site. The soil borrow material is being used to construct the temporary access road on the east side of Bayou Trepagnier for vehicle traffic and work access to the bayou sediment. The access road was completed and a floating bridge was installed across Engineers Canal to facilitate truck traffic in June and July.  Clean Zone excavation, water management, and solidification of bayou sediments commenced in August.  These activities continued through the typically dry and cool fall weather with minor interruptions due to isolated fronts.  Solidification of bayou sediments was completed mid-December; capping of stabilized bayou sediments with clay soil borrow material was completed in late December.  The access road footprint, clean zone area, and other areas  were dressed and graded and water control equipment removed from site in early January 2012.  The now capped former bayou channel  is  seeded with a interim rye grass cover and planting native vegetation species will ensue in coming weeks.




                                      Areial View of Bayou Trepagnier                                                   Bayou Trepagnier in Lower Reach


                                                                                    Sampling Sediment (Fall 2008) 

                     Testing soil mixing reagent (Summer 2010)                                          Overview of Pilot Cells              
                                                        Construction of access road along

                                               east side of Bayou, looking north (May 2011)  


                                                               Looking north from top of Hurricane Protection Levee:

                                                               Former Bayou channel now capped with soil (12-21-12)

Documents and Reports

Below are document links.  Click on the link to view the doucment


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