Wellhead protection

The Illinois EPA is expanding procedures for gathering driller's logs and safe yield information during the development of new community water supply wells. This brochure outlines a step-by-step approach for obtaining this information when installing new wells.

Once the Illinois EPA receives this new well data, a delineated Source Water Protection Area and lateral area of influence calculation will be provided to the community. This information can then be utilized as the technical support to initiate:

• maximum setback zones;
• eligibility for chemical monitoring reform/permanent monitoring relief;
• lab fee savings;
• prevention programs including the pollution prevention and conservation reserve programs

Community water supply systems expanding through the construction of new wells are required to initiate local wellhead protection programs for these wells. Traditionally this has included assurance that wells are properly engineered to protect against sanitary contamination. In September 1987, protection was expanded to include siting prohibitions for new drinking water wells locating proximate to certain high risk activities. Further, under 35 Ill Adm. Code Section 653.103(a) ¹, community water supplies are required to conduct safe yield and drawdown tests.

1 "The basic criteria for design of community water supply facilities shall be the Standards (Recommended Standards for Water Works as adopted by the Great Lakes-Upper Mississippi River Board of Sanitary Engineers)."

Delineation of the wellhead protection areas can be accomplished more readily and more economically at this time because much of the hydrogeologic and well production information that is gathered can also be used for resource assessment.

An inventory of potential sources and routes of contamination must be conducted within 1,000 feet of a new community water supply well. This must be completed prior to issuance of a permit to construct a water supply well ("C-1 Permit") by the Illinois EPA.

Yield and drawdown tests must be performed on every production well after construction or subsequent treatment and prior to placement of the permanent pump and issuance of an operating permit ("C-II Permit") by the Illinois EPA. The best possible information should be collected on the new community water supply well. This information must include the static and pumping water level information used in calculating drawdown. In addition, groundwater quality analysis is required. Further, detailed information and supporting documentation must be provided in the calculation of a long-term safe yield for the new well.

Supply the Illinois EPA the following information, specific to the new well under development:

• driller's and/or correlated well logs;
• regional groundwater flow direction (if available or conducted);
• results of tritium analysis (if available or conducted);
• static water level;
• depth of pump setting;
• test pump capacity - head characteristics;
• time of starting and ending each test cycle (preferably at least six hours with stable drawdown at a continuous pumping rate, normally 1.5 times the designed pumping rate);
• pumping water level at the end of the test cycle;
• pumping rate; and
• water recovery rate and levels
• aquifer property data
• groundwater quality analysis

In certain instances an aquifer test may be necessary to assess the effects of well interferences, determine if groundwater recharge area boundaries exist, or to assess an aquifer's long-term safe yield or vulnerability with respect to potential contamination sources. Once the Illinois EPA receives this data, a determination will be made on the degree of natural geologic protection afforded the well. Depending on the type of aquifer being utilized as a source, a confined or unconfined determination will be provided to the community.

Once operation of the new well is initiated, Community Water Supplies shall complete at least one set of laboratory analysis for volatile/synthetic organic and inorganic chemicals from the new untreated source. Upon completion of these analyses, the community water supply must file a revision to their waiver application, with all relevant information (including any necessary wellhead protection management activities) with the Illinois EPA.

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