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A series of annual geochemical models were created by RockWare utilizing RockWorks20 which were interpolated based on the 1,4-dioxane levels that were measured during 1986 through 2023. In cases where the same intervals were samples on more than one occasion during a given year, the highest 1,4-dioxane values were used. The extent of each annual model were limited to polygons based on only the wells that were sampled during the associated year to eliminate interpolating in areas where data is not present. The annual geochemical models were then filtered based on lithology to eliminate any voxels within the areas deemed impermeable based on lithology. The models were further constrained by utilizing the maximum historical water level surface (MHWLS) grid model to further restrict the interpolation from areas lacking measured data. Finally, the voxel models were converted to annual grid models, in which the cell values are based on the highest value within the corresponding column of voxels.
The 2023 plume presented here was created from the RockWorks project database files on February 27, 2024 (Gelman5_v2023.sqlite). The grid file titled 2023-01-01_to_2023-12-31.RwGrd was converted by The Mannik and Smith Group (MSG) to a raster file compatible in ArcGIS and converted to polygons of areas of concentrations between the following values: 4 ppb, 7.2 ppb, 85 ppb, 150 ppb, 280 ppb, 500 ppb, 1000 ppb, 1900 ppb, 3000 ppb, and 5000 ppb. The 7.2 ppb lines were created because it represents the current EGLE Part 201 generic residential cleanup criterion (GRCC). The 85 ppb lines were created to represent the Consent Judgement 3 (CJ3) drinking water criteria. The 280 ppb lines were created because that is the new EGLE groundwater-surface water interface (GSI) criterion, and 1900 ppb is the Vapor Intrusion criteria. EGLE is contouring the 4 ppb level because that could become a new trigger for response if detected in sentinel wells if the proposed 4th Consent Judgment is approved.
This data is used in the Gelman Site of 1,4-Dioxane Contamination web map (item details). If you have questions regarding the Gelman Sciences, Inc site of contamination contact Dan Hamel at 517-745-6595 or HamelD@michigan.gov. Report problems or data functionality suggestions to EGLE-Maps@Michigan.gov.