Illinois Administrative Code
Title 35 - ENVIRONMENTAL PROTECTION
Part 611 - PRIMARY DRINKING WATER STANDARDS
Subpart L - MICROBIOLOGICAL MONITORING AND ANALYTICAL REQUIREMENTS
Section 611.532 - Unfiltered PWSs
Current through Register Vol. 48, No. 38, September 20, 2024
If the Agency determines that filtration is required, it must specify alternative monitoring requirements, as appropriate, until filtration is in place. A supplier using a groundwater source under the direct influence of surface water not providing filtration treatment must monitor as the Agency directs in a SEP after determining under Section 611.212 that the supplier's groundwater source is under the direct influence of surface water, requiring the supplier to install and apply filtration treatment, and specifying appropriate monitoring requirements until filtration is in place.
a) The supplier must sample and analyze for fecal coliform or total coliform as Section 611.231(a) requires on representative source water samples it collects immediately prior to the first or only point of applying disinfectant. The supplier must sample for fecal or total coliforms no less frequently than Table B specifies each week the supplier serves water to the public. The supplier must also sample and analyze once for fecal or total coliform density every day the supplier serves water to the public and the turbidity of its source water exceeds 1 NTU (these samples count towards the weekly coliform sampling requirement), unless the Agency issues a SEP determining that the supplier cannot analyze within 30 hours after collecting the sample for logistical reasons outside the supplier's control.
b) The supplier must measure turbidity as Section 611.231(b) requires on representative grab samples of source water it collects immediately prior to the first or only point of applying disinfectant no less frequently than every four hours when the supplier serves water to the public. A supplier may substitute continuous turbidity monitoring for grab sample monitoring after validating the accuracy of regular the continuous measurement for accuracy using a protocol the Agency approved in a SEP.
c) The supplier must determine its total inactivation ratio for each day it operates based on the appropriate CT99.9 values in Appendix B. The supplier must monitor the parameters necessary to determine its total inactivation ratio using specific procedures:
d) The supplier must calculate total inactivation ratio using a specific procedure:
Ai = CTcalc/CT99.9
B = [SIGMA](Ai)
e) The supplier must continuously monitor the RDC of the water entering its distribution system and record the lowest value each day, except that the supplier may use grab sampling every four hours for no more than five days in lieu of continuous monitoring after a failure of the continuous monitoring equipment. A supplier serving 3,300 or fewer persons may take grab samples on an ongoing basis at the applicable frequency in Table C in lieu of continuous monitoring. If the RDC falls below 0.2 mg/L in a system using grab sampling in lieu of continuous monitoring, the supplier must take a grab sample every four hours until its RDC is equal to or greater than 0.2 mg/L.
f) Measuring Points
BOARD NOTE: This Section derives from 40 CFR 141.74(b).