Illinois Administrative Code › Title 8 - AGRICULTURE AND ANIMALS › Part 675 - GROUNDWATER USE GUIDELINES › Subpart B - GROUNDWATER WITHDRAWAL IN KANKAKEE, IROQUOIS, TAZEWELL, AND MCLEAN COUNTY SOIL AND WATER CONSERVATION DISTRICTS › Section 675.80 - Recommended Guidelines for the Construction of Wells and the Type and Setting of Pumps

Current through Register Vol. 48, No. 28, July 12, 2024
a) The
				district, with the assistance and approval of the Illinois Department of
				Agriculture, shall issue recommended guidelines for the construction of all
				groundwater withdrawal points, and the type and setting of pumps for use in
				those points of withdrawal (Section 5.1 of the Act). It is not the intent of
				these guidelines to supersede the Illinois Water Well Construction and Pump
				Installation Codes (77 Ill. Adm. Code 920 and 925), and all constructed wells
				and well pump installations shall comply with those Codes.
b) A natural consequence of groundwater
				withdrawal is drawdown in the source aquifer. An aquifer can safely support a
				certain amount of drawdown (called "allowable drawdown") without jeopardizing
				the availability of the regional groundwater resources. This allowable drawdown
				implies that there is a critical water level elevation for the aquifer. As long
				as the actual water level in the aquifer does not fall below the critical water
				level elevation, the aquifer resource remains protected. It is the intent of
				the recommended guidelines to promote construction of new wells which will
				provide an uninterrupted supply of water for reasonable use (see Section 4(g)
				of the Act and Section
				675.10
				) with the aquifer water level at or above the critical water level.
c) The recommended guidelines for the minimum
				aquifer penetration and pump intake settings, based upon aquifer type, shall
				be:
1) Unconsolidated or consolidated
				(bedrock) aquifers under artesian conditions: The minimum well penetration into
				the aquifer shall be 100% or 80 feet, whichever is less. The minimum pump
				intake setting shall be at or as close as possible to the top of the well
				screen for unconsolidated aquifers. For consolidated wells, the minimum pump
				intake setting shall be at the depth corresponding to 50% of the well's
				penetration into the aquifer. If instability in the bedrock aquifer precludes
				setting the pump intake at this depth, the pump setting shall be adjusted to a
				depth which alleviates the condition.
2) Unconsolidated or consolidated (bedrock)
				aquifers under water table conditions: The minimum well penetration shall be
				100% for these aquifers which can be fully penetrated within 100 feet of land
				surface or which are less than or equal to 50 feet thick. The minimum well
				penetration for aquifers greater than 50 feet thick shall be 50 feet or 50% of
				the aquifer thickness, whichever is greater. The minimum pump intake setting
				shall be at or as close as possible to the top of the well screen in
				unconsolidated aquifers. For consolidated wells, the minimum pump intake
				setting shall be at the depth corresponding to 50% of the well penetration into
				the aquifer. Note: The aquifer thickness is controlled by the saturated
				thickness of the permeable geologic materials. For a water table aquifer, this
				thickness changes throughout the year as the water table rises and falls in
				response to natural groundwater recharge and runoff. Therefore, the aquifer
				thickness for water table conditions used in determining the minimum well
				penetration will be the thickness which results with the natural average annual
				low water table at the point of withdrawal as obtained from scientific data on
				the aquifer, hydrology, and geology of the area.
3) Multiple or combined aquifers (both
				consolidated and unconsolidated): In some areas a hydraulic connection exists
				between more than one interval of water-bearing unconsolidated and/or
				consolidated deposits such that all deposits will respond in varying degrees to
				pumpage from a select few. The degree of interconnection can vary from deposit
				to deposit which influences both the response time and magnitude. In some
				cases, the interconnection allows several units to be treated collectively as
				one aquifer. In most cases, one deposit or a small group of deposits can be
				designated the primary aquifer whether it be the thickest, most permeable,
				deepest, or largest in areal extent. For multiple aquifers, the minimum well
				penetration and pump intake setting shall be used from the aquifer
				classifications (Subsections (c)(1) and (c)(2) of this Section) which
				correspond to the primary aquifer at each individual point of withdrawal. If
				designation of a primary aquifer is not possible, the minimum well penetration
				and pump intake setting shall be determined on an individual case by case basis
				in accordance with the scientific data on the groundwater aquifer, hydrology,
				and geology of the area as may be available from the well driller, Illinois
				State Water Survey, and State Geological Survey.