Cabot/Koppers Superfund Remediation Site Overview and Investigation Site history and background:
The Cabot Carbon-Koppers Superfund location is a past industrial place in Gainesville, FL. It legitimately stopped its processing and wood-treating actions in 2010. The site initially opened in 1912 and the approximately 90 acre site was utilized as a wood-treating facility for about 90 years. In fact, wood-treating process initiated with the usage of creosote in 1916 that basically was phased out of use in 1992. Throughout the 1960’s, two extra chemical treatments were also used which comprised chromated copper arsenate and pentachlorophenol. Throughout the functioning period, the chemical wastes were discharged and trickled onto the soil during processing as well of disposed of in unlined lagoons on Cabot/Koppers location. These particular wastewater lagoons have been roofed, and graded; although, for several years, they performed as major source zones for contamination to the top soil, surficial aquifer, subsurface soil matrix, as well as the Upper and Lower Hawthorne clay layers into that contaminants have entered. The Hawthorne Clay layers have also proceeded as a comparative barrier to the Upper Transmissive Region of the Floridian Aquifer, where there is also some indication of trace constituents of concern. The facility was proposed as a National Priorities List (NPL) in August of 1983. Ultimately, it was added to the list in September of 1984, therefore formally making the site a Superfund location, a location so contaminated with poisonous, toxic waste that it poses a threat to human wellbeing and the atmosphere. Monitoring of the potential fate and conveyance of pollutants, toxics in different phases has been a concern over the years with monitoring having begun prior to the site’s listing as a Superfund site.
The Cabot-Koppers Superfund place is situated at 200 NW 23rd Ave and the neighboring land has been industrialized over past few years in such a way that it has been zoned a diverse land-use area, zoned for housing, marketing , and civic land use. The surrounding area consists of marketable businesses, car dealerships, apartments to the north and south, and few residential houses to the west. The Gainesville Public Work facility also id situated on northeast of the Cabot carbon-Koppers when the area to the east is regularly not industrlized. Roughly 97, 600 people live within five to six miles of the facility. About 3.5 miles northeast of the Koppers facility lies the Gainesville Regional Utilities Murphree Well Field which supplies civic drinking water to the City of Gainesville as well as the adjacent Alachua County districts, processing at 28 million-gallons-per-day (MGD) Approximately 87% of the Well Field’s manufacture is from the Lower Transmissive Region of the Floridian Aquifer, and it serves approximately 168,200 people in that area. The primary goal of this report is to illustrate the time associated with the fate and conveyance of chromated copper arsenate (CCA), which is known as one the known chemical at the facility. Before determining CCA’s potential to infiltrate the Hawthorne Clay layers and enter into the Floridan Aquifer, thus posing a potential threat to the health and further treatment methods for the drinking water being pumped at the Murphree Well Field. Constituent of Concern Features: Chromated copper arsenate (CCA) is basically a chemical maintainer that is mainly utilized in the treatment of pressure-treated wood to preserve it from decomposition from different microbes or insects. This chemical compound comprises three different chemicals: chromium, copper, and arsenic are basically three primary, different kinds of this chemical. CCA is mainly recognized as one of the severe chemicals which has harmful, detrimental effects on human health and other inhabitants in the planet. Respiratory disease, ulcers, skin irritation, and carcinogen are the diseases that could possibly impact human’s life. In fact, the soil-water partition coefficients (Kd (L/kg) = Cabsorbed to soil/Cin water) for the three metal constituents that contains CCA are all similarly high. This simply indicates their hydrophobic nature and propensity to stay trapped within the soil/clay matrices. There have been some contaminations recorded in the Floridan Aquifer of arsenic (10 μg/L) in some samples). Although this is a natural mineral in the soil, it is still imprecise as to where the origin of the arsenic essentially derives. When drilling technique is applied in the construction of a monitoring and sampling well, oxygen actually enters in the water resulting in the desorption of arsenic from soil and into the water. The uncertainty arises from a well when it is constructed. In fact, some of the drilling mud mixed with the ground water and soil was randomly lost throughout the drilling. This actually has led to cross contamination within that well and shows the potential for future and supplementary sources and locations of cross contamination. For Instance, higher pH elevations have been noted at some of the Upper Floridian Aquifer monitoring wells that are possibly the result of cement grout utilized in the well construction that is eventually lost in the aquifer .Cement is recognized as one of the materials that is capable to enhance the water PH. It is crucial to be aware that arsenic could be extremely poisonous, toxic in high concentrations. EPA has regulated rules related to arsenics toxicity. Likewise, pH increases towards an alkaline ambient environment leading to desorption of both arsenite and arsenate from soil. This basically lets arsenic to become more portable within the aqueous phase.
Methodology:
Base of the Given the information that is written above, a theoretical model of the transport and fate of the constituent of concern (COC) and CCA, within the Upper Floridan Aquifer was formed by utilizing the software program Interactive Groundwater Modeling 3.5.9 (IGW). The model generally is applied to simulate the contaminant, pollutant plume which is produced transversely in the aquifer over time by the CCA. The particular model was run for a sufficient time s to let the plume and CCA concentration to dissolve in the aquifer until it reached the GRU Well Fields approximately 2.5 miles northeast of the source zone. On the shown figure that is shown below, the comparative difference in spatial extent between the well fields and the zone of surrounding the sites can be observed. Figure 1: Map of distance between GRU well fields being modelled and the Cabot/Koppers site

Figure 2: Potentiometric Surface for the groundwater surface underneath the Koppers site Results/Data Analysis: The following data is the result of the running Scenario 1 in the IGW software. In this scenario, there is no remediation and the plume is made over time by natural dispersion through the aquifer. Increased pumping from the GRU Morpheme Well Field tend to cause mobilizations increment as the hydraulic gradient increases. For the model simulation, the hydraulic gradient was assumed to be only 10 feet. Figure 8 shows the Gainesville area base-map input into IGW with the monitoring wells and the GRU Well Field drinking water wells. Figure 3: Base-map of the Gainesville area without remediation, noting GRU pumping wells and monitoring wells.

Figure 4: Plume generated by dispersion of CCA from constant contamination source and concentration with respect to time.

According to the graph, the plume reaches the GRU Well Field in approximately 77 years. Figures 5 through 9 show the mass concentrations of the COC in each of their individual monitoring wells. Figure 10 shows the plume mass balance and Figure 11 shows the water flux for the entire watershed area modeled. All the figures are made in the following pages.

Figure 5: Monitoring Well 131

Figure 6: Monitoring Well 130

Figure 7: Monitoring Well 129

Figure 8: Monitoring Well 127

Figure 9: Monitoring Well 126

Figure 10: CCA Plume Mass Balance without remediation treatment applied Figure 11: Water Flux in the watershed without remediation treatment applied

Remediation Solution:
For remediation, active recovery systems do not appear to be economically feasible .In fact there are abundant COCs related to the site and its historical land use which could hypothetically cause harm to the neighboring residents as well as the general population as a result of the surrounding areas current land use, an active pump and treat system was utilized in the simulation. Two remediation wells were placed to the northeast of the facility, each pumping 0.001075 MGD each. Figure 12 basically shows the base-map image uploaded for the watershed area with the remediation wells employed.
As shown by the IGW, the plume reaches the GRU Well Field in approximately 60 years. This assumption can be clarified by the increased hydraulic gradient caused by the augmented pumping near the Koppers facility. Figures 13 through 18 represent the concentrations in the monitoring wells after remediation was employed. Figure 19 shows the plume mass balance after remediation and Figure 20 shows the water flux for the whole watershed area modeled after remediation.

Figure 12: Plume generated by dispersion of CCA from constant contamination source and concentration over time with active pump and treat systems as a remediation technique

Figure 13: Monitoring Well 131

Figure 14: Monitoring Well 130

Figure 15: Monitoring Well 129

Figure 16: Monitoring Well 128

Figure 17: Monitoring Well 127

Figure 18: Monitoring Well 126

Figure 19: CCA Plume Mass Balance with remediation treatment applied

Figure 20: Water Flux in the watershed with remediation treatment applied

Cost Estimates:

Table 1: Summary of Remediation Cost and Unit Cost Data for 48 Sites Using Pump and Treat Systems to Recovery COCs.

Sources: FRTR and RTDF.

Conclusion:

By inspecting the plume concentrations, it is obvious that there is not much change, most probably a result of CCA having such a high average soil-water partition coefficient (500 L/kg). Although, it should be noted that the concentrations are not capable to dissolve as far as they were able to without active remediation. The amount of water pumped increases and should be utilized either in treatment or recirculation. Because the CCA concentrations are low within the dispersion area, it can be expected that drinking water standards are not a concern for treatment in the near future. Subsequently, the recommendation is to use passive treatment systems, as described earlier and to advance explore soil remediation techniques at the surface and within the surficial aquifer where contaminant levels are significantly higher according to current reports and literature. If more mobile or hydrophilic COCs are needed to be addressed, active treatment might be a better remediation method. Related to this model and case study, the costs incurred and water used are too great for active treatment to be recommended.