Marshfield Utilities discusses corrosion control and orthophosphate addition as lead-action deadline approaches

Marshfield Utilities staff told the commission the utility must install a corrosion control treatment system by the end of September to address a prior action-level exceedance for lead and copper. The stated preferred treatment is continuous orthophosphate addition, which forms a protective layer inside pipes and reduces lead leaching into drinking water.

Staff said the utility currently has about 689 full lead water services remaining. Options discussed included: (1) proceed with orthophosphate injection and associated design, bidding and construction (staff estimated roughly $150,000 for installation), (2) attempt a testing-out path that requires two rounds of 60 distribution samples (spring and summer) with a 90th-percentile threshold below 15 micrograms per liter to avoid full implementation, or (3) request an extension from the Wisconsin Department of Natural Resources (DNR) and the U.S. Environmental Protection Agency (EPA). Staff said the EPA response time and the likelihood of approval are uncertain.

Commissioners pressed for public-health information about orthophosphate, including how much phosphate remains dissolved in drinking water versus what becomes part of pipe scaling, and whether long-term ingestion poses health risks. Staff said testing reports show total lead results (dissolved plus particulate) but do not distinguish whether lead is present as a phosphate complex; lab reports do not explicitly measure "lead phosphate" as a distinct compound. Staff also noted that orthophosphate is naturally occurring, that typical orthophosphate injection rates discussed are on the order of 3 milligrams per liter (well below cited World Health Organization guidance figures mentioned in discussion), and that the treatment is intended as an interim measure until lead services are replaced.

Commissioners discussed accelerating lead-service replacements. At current replacement rates the staff estimated roughly five years to replace remaining private lead services (about 125–130 per year); with third-party acceleration commissioners said a two-year timeline might be feasible but would require substantial additional funding (staff referenced ballpark total replacement costs in the multi-million-dollar range). The commission asked staff to gather more information on health studies, the fraction of orthophosphate that remains in drinking water versus that which becomes scale, per-sample testing costs (staff estimated $10,000–$15,000 to run a testing round), and procurement timelines. No formal action was taken on orthophosphate at this meeting; staff will continue design and prepare for bidding while exploring testing and extension options.