Flint, Michigan Water Situation

Glossary

  • mg/L (ppm) = milligrams per Liter or parts per million
  • µg/L (ppb) = micrograms per Liter or parts per billion

Water Treatment Plant

The Town of New Castle's Millwood Water Treatment Plant (MWTP) receives its raw water supply primarily from the Catskill Aqueduct, which is fed by the Ashokan Reservoir located in the Catskill Mountains of upstate New York. This raw water source is low in alkalinity and hardness making it extremely soft and corrosive. Below are the annual averages for the raw water alkalinity, hardness and pH:

  • pH - 7.2
  • Hardness - 14 mg/L (ppm)
  • Alkalinity - 12 mg/L (ppm)

If left untreated, the corrosive characteristics of the raw water could corrode the homeowner's fixtures and pipes that may contain lead and copper, and allow lead and copper to dissolve into the water. However, the MWTP operates a very comprehensive three part program to prevent this corrosion from occurring. This program is detailed for you here.

Program

First Step

First, a chemical called Blended Liquid Orthophosphate is added to the treated water before it enters the distribution system. Blended Orthophosphate is a, food grade, corrosion inhibitor specifically designed to reduce lead and copper residuals at the tap and effectively minimize distribution corrosion. Blended Liquid Orthophosphate is ANSI/NSF (American National Standards Institute/ National Sanitary Foundation) approved product that also meets the AWWA (American Water Works Association) drinking water standards. When the Orthophosphate is added to the finished water it forms a protective layer on the interior of the piping. This protective layer acts as a barrier to corrosion, reducing dissolution of lead and copper into the water.

Second Step

Second, the pH range at which the applied, blended orthophosphate is most effective for minimizing lead solubility is 7.4 to 7.8. At the Millwood Water Treatment Plant we add Sodium Hydroxide to the finished water to raise the pH to 7.5. The Blended Liquid Orthophosphate is added to the finished water at a maintenance dose of 3 to 5 mg/L (ppm) and a residual of PO4 (phosphate) 1.2 mg/L (ppm) to 1.9 mg/L (ppm) is maintained throughout the entire distribution system. These maintenance dosages were recommended by the chemical manufacturer.

Final Step

Third, as a control procedure, a daily analysis is conducted on the entry point water and a sample is taken every day from different locations in the distribution system for corrosion control monitoring. Below are the average daily analytical results.

Finished Water

  • pH - 7.5
  • Hardness - 2 mg/L (ppm)
  • Alkalinity -17 mg/L (ppm)
  • Orthophosphate as (PO4) - 1.60 mg/L (ppm)

Distribution Samples

  • pH - 7.6
  • Hardness - 2 mg/L (ppm)
  • Alkalinity -18 mg/L (ppm)
  • Orthophosphate as (PO4) - 1.58 mg/L (ppm)

In addition to the daily monitoring, the New York State Health Department requires Biweekly Corrosion Control Monitoring of the entry point as well. Below are the averages for the first 4 months of 2016.

  • pH - 7.5
  • Hardness - 2 mg/L (ppm)
  • Alkalinity -16 mg/L (ppm)
  • Orthophosphate as (PO4) - 1.60 mg/L (ppm)

In addition to the Biweekly Corrosion Control monitoring, the Westchester County Health Department requires the Town to collect 10 distribution water samples from specific locations, twice a year, for corrosion control analysis. The samples are collected in May and September. Below are the average analytical results for the samples collected in 2015.

May

  • pH - 7.8
  • Hardness - 2 mg/L (ppm)
  • Alkalinity - 15 mg/L (ppm)
  • Phosphate, as PO4 - 1.41 mg/L (ppm)

September

  • pH - 7.6
  • Hardness - 3 mg/L (ppm)
  • Alkalinity - 19 mg/L (ppm)
  • Phosphate, as PO4 - 1.56 mg/L (ppm)

New York State Health Department regulations also require the Town to monitor their distribution system for Lead and Copper. Thirty samples are collected in June and the number of required sample sites is based on the population served. The results of the 30 samples are placed in ascending order from lowest concentration to highest. 

The number of samples are multiplied by 0.9 and the contaminant concentration of the number sample obtained by this calculation is the 90th percentile containment level. Provided are the June 2015 results for Lead and Copper. Typically more than 85% of the locations sampled were "non-detected" for lead.

Results

Results of compliance monitoring for the 90th percentile:

Level Detected

  • Lead 2.6 µg/L (ppb)
  • Copper 95.0 µg/L (ppb)

Action Level

  • 15.0 µg/L (ppb)
  • 1300 µg/L (ppb)

These results indicate that the Lead and Copper levels are well below the action level set by the New York Health Department and it clearly illustrates the effectiveness of the addition of Blended Liquid Orthophosphate and the Town's corrosion control monitoring. The Town of New Castle has remained well below and has not exceeded the action level for Lead or Copper in over 20 years; ever since the regulation went into effect.

In fact, the corrosion control monitoring program has been so effective that the Town's water system actually qualifies for both a reduced number of monitoring sites from 60 per year to 30 per year, and the Town could opt for monitoring only every three years instead of yearly. The Town made a conscious decision to accept the reduced number of monitoring sites option, but decided to retain the annual sampling and testing protocol to allow for a more complete evaluation of the ongoing success of the corrosion control program.