Correspondence between

Darren and Mike, The City of Flint and their engineering consultant would like EPA to provide a previously approved example of an optimal corrosion control treatment evaluation completed for a water treatment plant when full scale testing of the new source water was not available. This is in an effort to assist the City of Flint regarding the required corrosion control treatment evaluation of the City’s future change in source water to Lake Huron supplied by the Karegnondi Water Authority at the City of Flint Water Treatment Plant, as outlined in the Department’s October 30, 2015 letter to the City, and in accordance with the November 3, 2015, EPA Memorandum Lead and Copper Rule Requirements for Optimal Corrosion Control Treatment for Large Drinking Water Systems, both attached. While the later part of the EPA memo discusses systems that plan to disconnect from a supplier that had installed corrosion control treatment to determine the OCCT for the new source (and in the case of the City of Flint, new treatment), the guidance document that is referenced in this memo appears to focus only on existing systems where full-scale treatment evaluation is possible, with no apparent guidance for new systems or systems that disconnect from their supplier prior to their source and treatment change. Your assistance regarding this matter is greatly appreciated. Stephen Busch, P.E. MDEQ Lansing District Coordinator Office of Drinking Water and Municipal Assistance Lansing and Jackson District Supervisor 517-643-2314 buschs@michigan.gov xxxEND_PAGE:deq18_b217_1652_1652_1

his will surimarize our phone conversation of 10/19 and provide clarification regarding the previous comments. The City of Flint converted back te purchasing of Detroit Water and Sewerage Departrnent water on Friday Gctober 16, 2615. No indications of upset in the distribution systern have been reported to date. Detroit Water and Sewerage Department (DW5D} has confirmed the use of Innephas “Phosphoric Acid 7596 Technical” product which is NSF Standard 60 certified with a maximum allowable feed rate of 13 mg/L as product. The City of Flint will need to supaly a similar phosphoric acid product, NSF Standard 60 approved with allowable maximum dosage. DASE supplied water is currently dosed at 0.39 mg/L as PU1.2 mae/fl as PO4) slightly above DWSD’s OCCT requirement o dose a minimum of 0.9 mg/L as PO4 and have a minimum plant tap residual of 0.8 mg/l as PO4. DWSD plant tap residuals have been shown to consistently be at 0.39 mg/L as P OL2 me/b as PO4), In addition water supply entering Flirt has been tested and so far shown to contain approximately 0.39 me/i as POL? me/E as POS) as well, fo achieve pipe passivation Flint will boost orthophosphate dosage to establish @ rninimurn distribution residual of 1.0 mae/Las P (3.1 mg/h as POS), The chemical feed systern will be sized to achieve a dose up to 2.0 mg/L as Pi6.. mg/L as POd) in case orthophosphate foss is observed. Fling will continue Water Quality Parameter Monitoring in accordance with the LOR at the same 25 distribution locations used under the Flint River, in addition LO of these locations alsa serve as total colifarm monitoring sites, including disinfectant residual, and Flirt will be told te, for the purpase of assessing water stability, conduct water quality parameter monitoring along with turbidity and iron sarapling will be at these 10 locations ora weekly basis as suggested, This wil also ensure that a minimiurn recornmended ph levels are being maintained throughout the system, EPA ORD staff will provide instructions ta the City of Flint for creating test loans to help confirm effectiveness of the corrosion control treatment. This data will help in rebuilding public trust. The County Health Department and Mi Department of Health and Human Services will be conducting blood lead level esting of children in Flint. Chifdren with elevated blood lead levels will be offered exposure assessments of their homes, These assessrnants should inchide the contribution of lead fram service line and interior plurnbing sources. Such diagnostic testing should help further substantiate the effectiveness of corrasian contral reatment Procedures recommended by EPA should be shared with the Michigan Department of Health and Human Services, The University of Michigan in Ann Arbor had previously expressed interest in assisting the City of Flint. Both the Department of Chil and Environmental Engineering, and Schaal of Public Health should be contacted to determine if hat interest still exists with potential to assist in both test loop construction and monitoring, and exposure assessment monitoring in homes. Any water analysis should occur at a certified laboratory. xxxEND_PAGE:deq21_b122_0406_0411_2 The City will be required ta complete a6 month round of lead and copper compliance monitoring in the January ~ tune 2016 period, The City continues to offer all residents a first draw lead sarmple collection and analysis. Any additional staggered monitoring suggestions should be brought before the City’s Technical Advisory Committee. Criteria for deerning the treatment optimized must be established as the LOR only requires cornpliance with the lead and copper Action Levels once this determination has been made. The City of Flint is continuing to digitize service line index card records into a Geographic information System to confirm the location of lead service lines. EPA can provide additional information to the City regarding a sampling procedure to verify lead service line sites. The City’s engineering corsultant will need te evaluate RWA water in conjunction with the City of Flint treatment plant processes to determine any necessary adjustrnents in optimized carrasion contral treatment prior to initiating service te customin's. Full scale testing rnay not be feasible. Stephen Busch, PLE. MDEO Lansing (istrict Coordinater Office of Drinking Water and Municinal Assistance Lansing and Jackson District Supervisor BE? -643-2344 buschs@michigan.gov

Gentlemen, “Attached i is a timeline of events that led us to the recent boil water notice. It shows all sampling and results