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OHA Drinking Water Services
Contact Report Details |
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| PWS ID: | OR41 00248 | ||
| PWS Name: | DALLAS, CITY OF | ||
| Who Was Contacted: | Jake Dyer | ||
| Contact Phone: | 503-623-3446 (Email address hidden) | ||
| Contact Date: | 01/03/2025 | ||
| Contacted By: | HOFELD, EVAN (DWP) | ||
| Contact Method/Location: | |||
| Assistance Type: | WATER QUALITY ALERT RESPONSE | ||
| Reasons: | Disinfection Byproducts |
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| Details: | I received an alert on January 3, 2024 for a HAA5 result of 0.0607 MG/L from a sample collected at 1426 SE ANA ST (Site ID# 2DBP-03) on 11/21/24. I calculated the locational running annual average (LRAA) for 2DBP-03 to be 0.0359 (LRAA = [0.0607 + 0.0364 + 0.0312 + 0.0153] / 4) and the Operational Evaluation Level (OEL) to be 0.04725 mg/l for HAA5 (OEL = [(2 x 0.0607) + 0.0364 + 0.0312] / 4), which did not result in an RAA MCL or OEL exceedance. I emailed jake the calculations and two charts showing long-term trends of TOC and DBP data, noting that they appear to have had periodic high HAA5 results in the past, but then it drops back down, however, the peaks were gradually getting higher over time with a fair amount of variability of filtered water TOC despite relatively stable raw water TOC. I recommended taking paired raw and filtered water TOC samples to see how well the filters are removing TOC. I let Jake know that UV254 monitoring may also help evaluate filter performance with respect to organics removal and taking paired UV254/TOC results can help them see how well UV254 correlates with TOC levels. I let Jake know that no further actions are needed at this time other than to other than include the 0.0607 mg/l HAA5 result in the range of HAA5 results reported in their Consumer Confidence Report (CCR). Jake replied on 1-27-25 noting that they would start including raw and finished TOC samples with quarterly DBP sampling. Jake said he was also looking back at chlorine levels over the last few years which seemed to show that pre chlorine doses have been creeping up, causing a higher residual before the water hits the filters. He wasn't sure if this could contribute to higher DBP results or not and said they would make some adjustments and keep an eye on it. I responded that the goal is to reduce organics as much as possible through filtration prior to chlorination and should consider discontinuing pre-chlorination, but to consider CT and keep me posted. | ||
| Associated Alerts: | DBP-129 - 01/03/2025 - TOTAL HALOACETIC ACIDS (HAA5) |
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