Wanaque Reservoir Modeling Results

  • In response to the recommendation made by Jacobs Engineering in their May, 2016 Report on behalf of the NJDWSC, Cornerstone conducted the modeling of the Wanaque Reservoir and groundwater and surface water at the Site to assess the potential risk to the Reservoir based on actual groundwater and surface water quality at the Site.  Ford submitted the flow modeling report to the EPA, the Borough and NJDWSC. 

    Summary Description of BIOCHLOR Computer Model Conducted for 1,4-Dioxane:

    • Cornerstone utilized an industry-wide accepted model, the BIOCHLOR computer model, to model the groundwater transport of 1,4-Dioxane and potential attenuation along a groundwater flow pathway. 

    • Concentrations of 1,4-Dioxane in mine water in the deepest part of the PMP Air Shaft where the highest concentration of 1,4-Dioxane (148 ug/L) was reported and 1,4-dioxane concentrations in bedrock wells in the downgradient direction from the PMP Area that form a groundwater flow path from the PMP Air Shaft were put into the model.

    • By varying the input parameters during the various model “runs”, field-measurements of 1,4-Dioxane were compared to the model results to confirm that the model was constructed in a manner that accurately simulates actual geologic and hydrogeologic conditions in the subsurface aquifer at the Site. 

    • The BIOCHLOR model was also used to simulate the transport of 1,4-Dioxane in the CMP Area using the same input parameters used for the PMP Area and the actual 1,4-Dioxane concentrations reported in the CMP monitoring well with the highest 1,4-dioxane concentration (well RW-2).

    Findings/Results of BIOCHLOR Computer Model:

    • The results of the groundwater and surface water modeling conducted demonstrate that there is no risk to the Wanaque Reservoir from the Ringwood Site.

    • The results of the modeling consistently demonstrate that 1,4-Dioxane from the Site would not reach the Wanaque Reservoir.

    • These results were reached using very conservative assumptions and are consistent with the absence of 1,4-Dioxane in Ringwood Creek and the absence of 1,4-Dioxane in the Reservoir. 

    • Cornerstone used both measured concentrations generated by sampling and laboratory testing as well as the conservative analytical modeling as recommended by the Jacobs Report.

    • Importantly, the model indicates that 1,4-Dioxane will not reach the Wanaque Reservoir which is located much farther downgradient of the PMP Air Shaft and CMP well RW-2.

    • The model results indicate that 1,4-Dioxane concentrations in groundwater dissipate to non-detectable within 1,000 to 1,800 feet of the PMP Air Shaft and/or CMP well RW-2, well within the limits of the Site, even using very conservative assumptions.

    • The results of the modeling are consistent with the actual field data generated from sampling and laboratory analysis that indicate that 1,4-Dioxane in groundwater is contained on the Site.

    Other “Worst Case Scenarios Which Were Run Through the BIOCHLOR Model:

    • What if the groundwater with the highest 1,4-Dioxane concentrations in the mine water in the PMP Air Shaft somehow traveled unchanged and undiluted and discharged directly to the surface waters of Ringwood Creek at its downstream inlet to the Reservoir?

    Outcome:  The model shows that 1,4-Dioxane would still be non-detect in the surface water.  This is consistent with actual data that show that concentrations decrease in groundwater and surface water in the downgradient direction and that 1,4-Dioxane is not detected below Sally’s Ponds, Ringwood Creek, or the Reservoir (which is even further downgradient from these surface water bodies).

    • What if the 1,4-Dioxane concentrations in Park Brook immediately upstream of Sally’s pond were 2 times higher than the highest concentration documented by testing?

    Outcome:  The model shows that 1,4-Dioxane would still be non-detect in Ringwood Creek near the entrance to the Reservoir.

    • What if the highest reported concentration of 0.678 ug/L of 1,4-Dioxane (based on sample location SW-PAB-04 which is in Park Brook upstream of Sally’s Pond) migrated downstream in Park Brook past Sally’s Pond without mixing or dilution in the surface water such that the concentration remained unchanged?

    Outcome:  The model was run for this “worst case scenario” and the results still showed that the 1,4-Dioxane would not reach the Reservoir.  This is consistent with the last 3 rounds of sampling at this location which were non-detect.  This is a very conservative analysis given that mixing does and will occur in the surface waters naturally in the downstream direction.

    • What if 1,4-Dioxane were detectable in Ringwood Creek at the Reservoir inlet (even though it has not been and the model results show it will not be)?

    Outcome:  Since the flow contribution from the Ringwood Creek to the Wanaque Reservoir ranges from 2% to 23% depending on the month and year (based on actual data provided by the NJDWSC), the model shows 1,4-Dioxane it would again be non-detect in the Wanaque Reservoir even at the highest range of flow contribution from the Ringwood Creek (i.e. 23%).