March 13, 2019
Susan Laitsch
Introduction
Tallahassee, Florida, was established as the State Capital in 1823 (Robertson, 2001) as it was half way between the two existing settlements at the time. It was here that the Cascades waterfall was located, depicted only once by Compt Francis Castelnau’s drawing in 1839. The waterfall acted as the primary meeting place until it was consequentially destroyed in 1855 by the development of the Pensacola/Georgia Railroad which ran along the St. Augustine creek bed (Robertson, 2001). Population growth and an increased demand for energy prompted the Federal government to establish the Rural Gasification Program. This in turn instigated the establishment of a Manufactured Gas Plant (MGP) (located at what is now Cascades Park) by the City of Tallahassee. This paper will discuss the political, environmental, and topographic history of Cascades Park from 1895 – 2019 and the processes that allowed for its remediation following the MGP.
FUNCTION OF MGP’S
Manufactured gas plants produce synthetic fuel gas by three main processes: coal carbonization, carbureted water gas (CWG), and oil gas (Heritage Research Center, 2002) In the case of the Cascade Park Gasification Plant, both coal carbonization and water gas processes were used to produce gas for heat/light energy.
Coal carbonization was used as the primary method for producing synthetic coal gas prior to 1875 (Heritage Research Center, 2002). In this process gas was produced by destructive distillation of bituminous coal which involved the heating of coal in an anaerobic environment, or in the case of MGP’s, retorts. This effectively broke down the coal into its volatile components, resulting in roughly 20% (based on weight) of the original coal being converted to gas (Schobert, 1987). The remaining coal was converted into solid byproducts, the majority of which was coke. After distillation, the volatile gases were collected, cooled, and purified resulting in usable coal gas and contaminated waste.
The carbureted water gas process was later developed by Thaddeus S. C. Lowe in 1873 (Heritage Research Center, 2002). In this method, oil was injected into a retort containing gas produced by destructive distillation of coke/coal and thermally cracked causing it to bond to the coal gas. This mixture was then cooled and purified to produce water gas (and waste). Although similar to coal goas, water gas had a higher thermal content, or calorific value, than coal gas (Miller, 2005) meaning it could provide more energy per unit volume.
History and Duration of the Cascades Coal Gasification Plant
The Cascade Park Gasification Plant was built by the City of Tallahassee in 1895 (Robertson, 2001) and operated until its closure in the late 1950s. Throughout the plants operation, waste and contaminants produced – including polycyclic aromatic hydrocarbons (PAHs), BTEX chemicals (benzene, toluene, ethylbenzene, and xylenes), naphthalene, 1-methylnapthalene, 2-methylnapthalene, coal tar, and arsenic – were disposed of inadequately in adjacent pits, lagoons, or landfills. Consequently, sub/surface soil and sediment/ground water in these locations showed elevated concentrations of PAHs, acenaphthene, BTEX (United States Environmental Protection Agency, 2017). In 1924 contaminated soil was used to build Centennial Field, which was used between 1926-1971 (Robertson, 2001). The MGPs wastes were also deposited in the Cascade Landfill, which was operated from 1928-1936. In total, contaminated surface area of the MGP site, landfill, and Centennial Field covered approximately 9.8 acres (United States Environmental Protection Agency, 2002).
In 1971, following the acquisition of the Cascade Park Gasification Plant and Centennial field by the state of Florida in 1963, new legislation declared the area Cascades Park in tribute to the location’s history. The MGP was subsequently demolished in 1974 and remained vacant until a holding pond was excavated in 2006 (Robertson, 2001). Construction of the current Cascades Park commenced four years later in 2010, until its completion is 2014.
Remediation Efforts and Magnitude of Contamination
Governmental concern regarding rural gasification sites began in the late 1970’s with the commencement of a nationwide investigation of MGPs by the Environmental Protection Agency (Robertson, 2001). Analysis of the Cascade Park Gasification Plant was first managed by both responsible parties of contamination, each previous site owners, the State and City. In 2002 the City continued investigations/response actions under the supervision of the EPA after entering into a Superfund alternative approach (SAA) agreement…” (United States Environmental Protection Agency, 2018). From 1999-2002 the above parties conducted an Engineering Evaluation/Cost Analysis (EE/CA) which was later approved in 2004. In 2003 the EPA released an Action Memorandum that identified Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) removal actions to mitigate soil, sediment, and groundwater contamination (United States Environmental Protection Agency, 2017).
Following the initial investigations and suggested removal actions regarding the site contamination levels/locations, a Non-Time Critical Removal action was conducted in 2006. Approximately 347.59 tons of sediment from Cascade Creek, and roughly 84,551.69 tons of ground soil was excavated and taken to a licensed landfill in Georgia (McCarthy, 2013). Residual contamination was capped thus determined to be of minimal risk. From 2007 – 2011 Monitored Natural Attenuation (MNA) was conducted for groundwater which showed an increase in contamination levels. As a result, the City conducted a Focused Remedial Investigation and Feasibility Study (RI/FS) of groundwater from 2011-2012 devising a final RI/FS work plan in March 2012. An Updated Remedial Investigation/Risk Analysis (RI/RA) was completed in November of the same year. Bench & pilot studies regarding in-situ chemical oxidation were implemented from January – August 2013. Bench testing results indicated un-activated persulfate was effective for groundwater treatment. In 2013, 68,500 gallons of a 5% sodium persulfate solution were injected on site at depths ranging from 90 – 140 feet below sea level with a flowrate of 5 – 10 gallons/minute at 10 PSI. Results showed a decrease in contamination and chemicals of concern succeeding injections.
Cascade Park officially opened in March 2014, subsequent to which groundwater contamination decreased rapidly as shown by annual NAM results collected from 2012 – 2017. 2017 contamination levels were measured below ‘health-based clean-up levels’ (United States Environmental Protection Agency, 2018) and by February 5, 2019 the United States EPA issued a no further action Record of Decision (ROD) effectively completing the remediation process.
Conclusion
Over the course of roughly 120 years the use of the land which now comprises Cascade Park had shifted dramatically. A once natural landscape was squandered by a coal gasification plant with harmful waste which forced remediation efforts. Thus, Cascade Park became a superfund site followed by the eventual opening of the environmentally healthy and ‘smart’ park that exist today. Through years of work, the land contaminated by the Cascade Coal Gasification Plant was able to undergo a dramatic remediation finally resulting in a 25 acre park (Kim, 2018) designed to prevent flooding, provide recreational activities, and increase livability.
Works Cited
Heritage Research Center, Ltd. (2002). A Brief History of the Manufactured Gas Industry in the United States. Retrieved from http://www.heritageresearch.com/documents/More%20Ab out%20Manufactured %20Gas.pdf
Kim, G. (2018). An integrated system of urban green infrastructure on different types of vacant land to provide multiple benefits for local communities. Sustainable cities and society, 36, 116-130.
McCarthy, A. J. (March 22, 2013). State of Florida Manufactured Gas Plant AKA: Coal Gasification Plant Assessment and Remediation Status. Retrieved from https://floridadep.gov/sit es/default/files/MGP-draft-update_22Mar13_0.pdf
Miller, B. G. (2005). Coal energy systems. Academic Press
Robertson, J. O. (2001). A History and Case Study of Government Relations concerning Cascade Park. Tallahassee, FL: FCRC Consensus Center.
Schobert, H. H. (1987). Coal: The energy source of the past and future.
SIS, E. (2014). Florida Park Provides Flood Control, Recreation, and Entertainment. Civil Engineering.
United States Environmental Protection Agency. (March, 2002). Superfund Proposed Plan Fact Sheet, Cascade Park Gasification Plant/Cascade Landfill, Removal Action Memorandum, U.S. EPA Region IV, Tallahassee, FL, March 2002. Retrieved from https://web.archive.org/web/20030627134444/http://www.epa.gov/region4/waste/npl/nplfln/cascade.pdf
United States Environmental Protection Agency. (October 20, 2017). Cascade Park Gasification Plant Tallahassee, FL, Cleanup Activities. Retrieved from https://cumulis.epa.gov/superc pad/SiteProfiles/index.cfm?fuseaction=second.cleanup&id=0404729
United States Environmental Protection Agency (July, 2018). Superfund Proposed Plan, Cascade Park Gasification Plant and Cascade Park Landfill Sites. Retrieved from https://semspub.epa.gov/work/04/11094739.pdf