Sodium Hydroxide Release, Wilmington, Ohio

The Challenge:

A CSX Transportation (CSXT) train derailment near Wilmington, Ohio in June 2001 released approximately 28,500 gallons of sodium hydroxide (NaOH) solution into Cowan Creek.  The derailment occurred approximately 1½ miles upstream of Cowan Lake State Park.  Immediate concerns were for acute exposure to aquatic organisms, to persons using the creek and lake for recreation, and long-term ecological effects. 

The Response:

Emergency response cleanup efforts were coordinated by CSXT, state and local officials and ARCADIS personnel managed and implemented containment and remedial activities at the site.  In order to contain the NaOH and reduce water flow, six temporary earth and rock dams were constructed both upstream and downstream of the release.  These dams provided settling points for the solution, as it was heavier than water. Remedial response activities focused on 1) removal of the NaOH solution using vacuum tankers; 2) monitoring surface water pH in Cowan Creek and Cowan Lake; and 3) neutralizing the surface water pH. 

Creek water pH neutralization was completed with the addition of diluted solutions of citric and/or glacial acetic acid by one of three methods:  1) batch treatment where creek water mixed with NaOH was pumped into tanks, neutralized and released back into the creek; 2) continuous flow through treatment where acetic acid was continuously pumped into pipes that flowed through the dams; and/or 3) localized treatment where diluted citric acid was hand-pumped directly to NaOH pockets near the creek bottom.   To better utilize the natural buffering capacity, seven pumps were spaced along the creek downstream to facilitate the mixing of creek water.   Neutralization and pH monitoring activities were conducted round-the-clock for five consecutive days and surface water pH and sediment pH were monitored for 12 days after the derailment.

Once initial remedial response activities were complete ARCADIS assessed the potential impacts to the creek and the lake as they related to environmental impact, human heath, and future use of the State Park facilities.  Assessments included: 1) A thorough physical and ecological description of the study area, including ecoregion, watershed and aquifer identification; 2) Pre-release ecological status of Cowan Creek and Cowan Lake, including habitat evaluations, land use, point and non-point discharge identification and beneficial use designation attainment; 3) Post-release ecological status of Cowan Creek and Cowan Lake, including effects on surface water, sediment, aquatic biota and the riparian corridor of the creek; 4) Human health exposure evaluation, including exposure scenario identification; and 5) A five-year human use comparison to a similar state park.

The response activities at the derailment site and locations downstream required the construction of access corridors and work areas along the undeveloped tracts of Cowan Creek.  After completion of the response, ARCADIS coordinated bank and flood plain restoration activities in the access corridors and work areas.  Indigenous tree species and shrubs were replaced and stream bank grading was completed to pre-incident conditions.

The Result:

Initial emergency response efforts were successful in mitigating the impacts to Cowan Creek from the release and no impact was observed in Cowan Lake.  Response activities reduced pH to background levels in Cowan Creek within six days of the release. ARCADIS was able to demonstrate to the Ohio Environmental Protection Agency (EPA) that although the NaOH release resulted in an acute fish kill in Cowan Creek, no ecologically relevant alterations to the biological community of Cowan Creek were observed. Additionally, ARCADIS demonstrated that that the NaOH release did not adversely affect human health or human use at Cowan Creek State Park.  A summary report was submitted to the Ohio EPA in September 2002 that documented the response, restoration, and rebound of Cowan Creek.  In January 2003, Ohio EPA provided a "No Further Action" status for the site.