Section 372.500  Groundwater Monitoring

a)         General

1)         Saturated zone groundwater monitoring shall be provided for all land application systems.  A minimum of three groundwater monitoring wells must be provided, one upgradient for determining background concentrations and two downgradient in the dominant direction of groundwater movement from the land application system.

2)         Provision shall be made for sampling of the discharge from any drainage tiles underlying the application area.

b)         Potable Water Supply Wells

            Where the project site is within 1,000 feet of existing potable water wells but the wells are outside the minimum setback zone of the Illinois Groundwater Protection Act [415 ILCS 55], groundwater monitoring wells must be provided between each potable water well and the land application system.

c)         Monitoring Well Design

            The monitoring wells shall be constructed with provisions for sampling at the surface of the water table and at 5 feet below the water table at each monitoring site.

d)         Testing and Monitoring Equipment

            Provision shall be made for testing groundwater for nitrates, ammonia nitrogen, chlorides, sulfates, pH, total dissolved solids, phosphate, and coliform bacteria as specified by the Agency permit for the project to measure compliance with groundwater standards.  Testing shall be performed in accordance with 40 CFR 136 (1992) (no later amendments or editions), and may be done either at an onsite laboratory or through a contractual arrangement with an offsite laboratory.