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OHA Drinking Water Services
Contact Report Details |
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| PWS ID: | OR41 00149 | ||
| PWS Name: | BROOKINGS, CITY OF | ||
| Who Was Contacted: | Mark Haglund | ||
| Contact Phone: | 541-412-0424 (Email address hidden) | ||
| Contact Date: | 02/13/2019 | ||
| Contacted By: | PARRY, BETSY (DWP) | ||
| Contact Method/Location: | Phone | ||
| Assistance Type: | MONITORING | ||
| Reasons: | GWR |
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| Details: | DWS data entry staff were unsure how to interpret a note attached to the January GWR 4-log treatment form. Their disinfection contact chamber is a 2.5-mile long pipe running from their source to the WTP – they add chlorine at the source, then measure it as it enters the plant down below. The approved monitoring location to meet the GWR 4-log disinfection standard is as it enters the plant. They had reported that the chlorine level at this location was <0.2 mg/L (their min. for 4-log treatment) for a span of 6.25 and 7.5 hrs, respectively, on 2 days in January, though the plant was actually pumping for a small part of that time (<2 hrs & < 1 hr). Pumping time is not relevant to compliance- only the max period during operations when the min. residual was not met. Later (in March), they submitted more data showing that in January, there was no 4-hour period when the min. residual was below the requirement for GWR 4-log treatment (so no Tier 2 violation for January). The situation was also confused by the fact that the GWR 4-log form has a column heading called "Lowest free chlorine residual at entry point to distribution system" for recording post-disinfection chlorine levels. However, in the case of Brookings, the post-disinfection chlorine level comes after their contact chamber (i.e., the chlorinated line bringing water to the plant). This water system ALSO injects chlorine for residual maintenance purposes before it leaves the plant (which is usually the "entry point"). For 4-log tmt reporting, OAR 333-061-0036(11)(b)(A) says that "at groundwater systems serving more than 3,300 people, water suppliers must continuously monitor the residual disinfectant concentration... at a location approved by the Authority." Because they are recording it at the OHA-approved location, we may consider editing the column heading on their form so that it says to enter readings there (in this case, where the chlorinated water enters the plant) rather than at the EP. |
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