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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: | Yvonne Mazza Jacobs | ||
| Contact Phone: | 303-985-8579 (Email address hidden) | ||
| Contact Date: | 10/30/2019 | ||
| Contacted By: | PARRY, BETSY (DWP) | ||
| Contact Method/Location: | |||
| Assistance Type: | SURVEY/DEFICIENCY FOLLOW-UP | ||
| Survey: | 10/31/2018 | ||
| Reasons: | GWR |
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| Details: | Yvonne had proposed two possible locations for a "raw water" tap. For either one, the raw water would be obtained operationally, i.e., they would still chlorinate into the Ranney Well, turn off the chlorinator and pump to waste in order to "clear" the chlorine before collecting a "raw" sample. In a test run, it took 1 hour 15 minutes to go from 0.6 mg/L free chlorine to zero residual. Although not ideal, this method is acceptable to meet the federal Groundwater Rule. For their consideration, I emailed some reasons why it is not ideal: • The sample would not be truly representative of the raw water quality in the area, as compared to a sample obtained in a location that does not usually experience continuous chlorination. For example, there would likely be scarce representation of microbes that normally live in groundwater, even though they may not pose health risks. It is not a perfect solution. • Although not required based on their water system’s current classification as GW, there may be future instances in which this version of a raw water sample tap will not work out. For example, if an Microscopic Particulate Analysis (MPA) test were required (say, based on changes in river flow or floodplain configuration), this arrangement would require pumping to waste for several hours before beginning the MPA test in order to truly represent the suite of microorganisms present. Another possibility is if Brookings ever wanted to monitor for cyanobacteria. Any trace chlorine could lyse the cell walls, making it hard to identify the type of cyanobacteria present and therefore whether they posed a risk. • Public water systems may want to (or may be asked to) conduct more types of raw water sampling in the future. Yvonne later informed me their choice of location - they will install a "raw" water monitoring tap at each of the 3 turbine pumps (that extract water from the Ranney Well). |
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