Section 734.325  Stage 3 Site Investigation

The Stage 3 site investigation must be designed to identify the extent of off-site soil and groundwater contamination that, as a result of the release, exceeds the most stringent Tier 1 remediation objectives of 35 Ill. Adm. Code 742 for the applicable indicator contaminants.

a)         The Stage 3 site investigation must consist of the following:

1)         The drilling of soil borings and collection of soil samples necessary to identify the extent of soil contamination beyond the site's property boundaries that exceeds the most stringent Tier 1 remediation objectives of 35 Ill. Adm. Code 742 for the applicable indicator contaminants.  Soil samples must be collected in appropriate locations and at appropriate depths, based upon the results of the soil sampling and other investigation activities conducted to date, provided, however, that soil samples must not be collected below the groundwater table.  All samples must be analyzed for the applicable indicator contaminants; and

2)         The installation of groundwater monitoring wells and collection of groundwater samples necessary to identify the extent of groundwater contamination beyond the site's property boundaries that exceeds the most stringent Tier 1 remediation objectives of 35 Ill. Adm. Code 742 for the applicable indicator contaminants.  If soil samples are collected from a monitoring well boring, the samples must be collected in appropriate locations and at appropriate depths, based upon the results of the soil sampling and other investigation activities conducted to date, provided, however, that soil samples must not be collected below the groundwater table.  All samples must be analyzed for the applicable indicator contaminants.

b)         The Stage 3 site investigation plan must include, but is not limited to, the following:

1)         An executive summary of Stage 2 site investigation activities and actions proposed in the Stage 3 site investigation plan to identify the extent of soil and groundwater contamination beyond the site's property boundaries that exceeds the most stringent Tier 1 remediation objectives of 35 Ill. Adm. Code 742 for the applicable indicator contaminants;

2)         The results of the Stage 2 site investigation, including but not limited to the following:

A)        One or more site maps meeting the requirements of Section 734.440 that show the locations of all borings and groundwater monitoring wells completed as part of the Stage 2 site investigation;

B)        One or more site maps meeting the requirements of Section 734.440 that show the locations of all groundwater monitoring wells completed to date, and the groundwater flow direction;

C)        One or more site maps meeting the requirements of Section 734.440 that show the extent of soil and groundwater contamination at the site that exceeds the most stringent Tier 1 remediation objectives of 35 Ill. Adm. Code 742 for the applicable indicator contaminants;

D)        One or more cross-sections of the site that show the geology of the site and the horizontal and vertical extent of soil and groundwater contamination at the site that exceeds the most stringent Tier 1 remediation objectives of 35 Ill. Adm. Code 742 for the applicable indicator contaminants;

E)        Analytical results, chain of custody forms, and laboratory certifications for all samples analyzed for the applicable indicator contaminants as part of the Stage 2 site investigation;

F)         One or more tables comparing the analytical results of the samples collected to date to the most stringent Tier 1 remediation objectives of 35 Ill. Adm. Code 742 for the applicable indicator contaminants; and

G)        For soil borings and groundwater monitoring wells installed as part of the Stage 2 site investigation, soil boring logs and monitoring well construction diagrams meeting the requirements of Sections 734.425 and 734.430 of this Part; and

3)         A Stage 3 sampling plan that includes, but is not limited to, the following:

A)        A narrative justifying the activities proposed as part of the Stage 3 site investigation; 

B)        A map depicting the location of soil borings and groundwater monitoring wells proposed to identify the extent of soil and groundwater contamination beyond the site's property boundaries that exceeds the most stringent Tier 1 remediation objectives of 35 Ill. Adm. Code 742 for the applicable indicator contaminants; and

C)        The depth and construction details of the proposed soil borings and groundwater monitoring wells.

c)         Upon completion of the Stage 3 site investigation the owner or operator must proceed with the submission of a site investigation completion report that meets the requirements of Section 734.330 of this Part.