Post on 21-Jul-2016
description
Page 1 of 2
RACER Site, Lansing, Michigan 1,4-‐Dioxane in Groundwater For nearly three years, RACER has been performing comprehensive environmental studies at Plants 2, 3 and 6 at the former General Motors facility in the City of Lansing and Charter Township of Lansing, Michigan (the Site). Under the oversight of the Michigan Department of Environmental Quality
(MDEQ), the studies have consisted of extensive sampling across the three plants and collection of soil and groundwater samples for laboratory testing. As RACER was nearing completion of the investigation in mid-‐2013, a substance called 1,4-‐dioxane was detected in groundwater samples collected from a depth of about 65 feet on a portion of former Plants 2 and 3.
1,4-‐dioxane is primarily used as an additive to stabilize industrial solvents for storage and dissolves
easily in water. When a solvent containing 1,4-‐dioxane is accidentally released into the environment, 1,4-‐dioxane dissolves in groundwater and can move with the groundwater to form long plumes. In an environmental investigation, a plume refers to an area of groundwater containing chemicals moving with groundwater. The size, direction and speed a plume travels depend on groundwater flow
patterns. The investigation work completed at the Site has established the size of the 1,4-‐dioxane plume and how it is moving. The location of the 1,4-‐dioxane plume is shown on the figure on the back of this page.
The key conclusions about the 1,4-‐dioxane plume at the Site are summarized below:
• The 1,4-‐dioxane plume does not extend to the municipal water supply wells and, for a variety of geological reasons, is not likely to affect those municipal drinking water supply wells in the
future. Sampling of municipal wells to date has not detected the presence of 1,4-‐dioxane. • The plume is located 65 to 80 feet below the ground in groundwater located above the
deeper bedrock drinking water aquifer. • The plume is more than 30 years old and is generally moving slowly to the south at an
average rate of 50 feet per year. • Groundwater monitoring will continue at the Site to verify that these conditions do not
change.
RACER has worked closely with the MDEQ, West Side Water, the Lansing Board of Water & Light, City of Lansing, and Charter Township of Lansing officials to develop a proposed remediation plan to
address contamination at the Site, including the 1,4-‐dioxane plume. After the proposed plan is reviewed by MDEQ, it will be available for public review and comment. RACER will implement a remedial plan when approved by MDEQ.
RACER Trust Public Informational Meeting
Lansing and Lansing Townsip July 8, 2014
2012 Site Activities, Plants 2, 3, and 6:
As part of the Resource Conservation and Recovery Act (RCRA) Facility Investigation (RFI) Phase 2 completed between April and December 2012, the following activities were completed:
• Installation of: o 6 bedrock monitoring wells, o 15 shallow monitoring wells, and o 11 light non-aqueous phase liquid (LNAPL) monitoring wells.
• Completion of: o 81 Laser Induced Fluorescence (LIF) borings, o 52 vertical aquifer profile (VAP) and/or Hydraulic Profiling Tool (HPT) borings, and o 310 shallow soil borings.
• Installation of 4 soil gas monitoring points. • Collection of:
o 1,257 soil samples and o 221 groundwater samples (excluding routine groundwater monitoring samples).
2013 Site Activities, Plants 2, 3, and 6:
The RFI Phase 2 investigation culminated in the submittal of the RFI Phase 2 Summary Report to the MDEQ in February 2013. Based on the results of the RFI Phase 2, additional work was completed at the Site including the lower 1,4-dioxane investigation, additional investigation for metals, and investigation of various utility corridors. As part of the investigation the following activities were completed:
• Installation of 3 bedrock monitoring wells, 24 deep overburden monitoring wells and 5 shallow/perched monitoring wells.
• Completion of 41 deep VAP soil borings. • Completion of 15 shallow soil borings. • Collection of 43 groundwater samples. • Collection of 93 soil samples • Sampling of one Lansing Township municipal water supply well and one Board of Water and Light
municipal water supply well. • Quarterly groundwater sampling from monitoring wells
2014 Site Activities, Plants 2, 3 & 6:
The following has been completed to date in 2014:
• Submittal of an RFI Phase 2 Supplemental Activities Summary Report to MDEQ. • Submittal of a Preliminary Groundwater Geochemical and Plume Stability Assessment Report to MDEQ. • Submittal of a Revised Interim Groundwater Monitoring Plan to MDEQ. • Completion of a groundwater hydraulic study on the lower 1,4-dioxane plume to verify groundwater flow
and the potential effects of municipal pumping on groundwater trends at the Site. • Sampling of three additional Lansing Township municipal water supply wells and two Board of Water and
Light municipal water supply wells for 1,4-dioxane. • Submittal of a Draft Corrective Measures Study (CMS) to MDEQ.
Corrective Measures Study (CMS), Plants 2, 3, and 6:
After assessing the information from the site investigation and considering various alternatives, the proposed final corrective measures for the Site include:
• Land Use Restrictions: Limit future use of the properties to commercial and/or industrial land use only. • Groundwater Use Restrictions: Prohibit the use of groundwater for drinking, irrigation, or other
purposes on-site. • Monitored Plume Stability: Implement a long term groundwater monitoring program. Groundwater
plumes to be monitored over time to verify they are stable or shrinking. • Clean Cover/Caps: Utilize clean covers and caps to prevent potential exposure to impacted soils on-site. • Targeted Excavations: Excavations will be completed at several areas of the Site to eliminate soil and
groundwater impacts located near the property boundaries. • 1,4-Dioxane in Deep Groundwater: Installation of a groundwater treatment system to address the deep
1,4-dioxane located beneath Plants 2 & 3.
Further Evaluations/Interim Measures:
• Investigation to further define the source area for the lower 1,4-dioxane plume. The data collected will be used to aid in the design of the treatment system.
• Hydraulic testing of the lower aquifer. Data will be used to assist in the design of a groundwater treatment system.
• Groundwater monitoring will continue on a routine schedule to monitor the effectiveness of corrective measures.