Ill. Admin. Code tit. 35, § 734.445
a) At a minimum, the owner or operator must conduct a water supply well survey to identify all potable water supply wells located at the site or within 200 feet of the site, all community water supply wells located at the site or within 2,500 feet of the site, and all regulated recharge areas and wellhead protection areas in which the site is located. Actions taken to identify the wells must include, but not be limited to, the following:
b) In addition to the potable water supply wells identified pursuant to subsection (a) of this Section, the owner or operator must extend the water supply well survey if soil or groundwater contamination exceeding the Tier 1 groundwater ingestion exposure route remediation objectives of 35 Ill. Adm. Code 742 for the applicable indicator contaminants extends beyond the site's property boundary, or, as part of a corrective action plan, the owner or operator proposes to leave in place soil or groundwater contamination exceeding the Tier 1 groundwater ingestion exposure route remediation objectives of 35 Ill. Adm. Code 742 for the applicable indicator contaminants and contamination exceeding such objectives is modeled to migrate beyond the site's property boundary. At a minimum, the extended water supply well survey must identify the following:
1) One or more maps, to an appropriate scale, showing the following: