Water recreation activities resume at White Rock Lake

On March 24, Dallas Park and Recreation resumed water recreation activities at White Rock Lake after Dallas Water Utilities (DWU) reported water sampling results were within normal weather-related, pre-incident levels. Park visitors can enjoy activities like fishing, boating, and rowing. While swimming remains prohibited, the water launch area at White Rock Lake Dog Park is available for pets.

Following best practices, park officials will continue receiving testing data from DWU and will enact its maintenance operations protocols for restricting water recreation activities if water quality deteriorates from upstream incidents and major weather storms.

DWU began sampling White Rock Creek and White Rock Lake immediately following the sewage overflow in Plano that occurred on Thursday, March 14. E. coli sample results showed that two days immediately following the overflow, on March 16, levels were at the maximum detectable limit of 2419.6 MPN (most probable number) at the Mockingbird Lane site where White Rock Creek enters White Rock Lake. The E. coli levels were also elevated at 776 MPN around the lake near the White Rock Pump Station on March 17; near the Bath House Cultural Center on March 18 and 19, the levels were at 538 MPN and 794 MPN after the overflow made its way to these locations. On March 16, prior to the sewage overflow reaching those two locations, the E. coli levels were 201MPN at the pump station and 130 MPN at the Bath House.

E. coli levels continued to improve as further sampling by DWU continued. E. coli levels from the White Rock Creek at Mockingbird Lane site improved to 187 MPN on March 24. There were two noticeable spikes in the E. coli levels at this location, but those instances occurred on or immediately following rain events on March 22 and 25. The cultural center and pump station sites also saw a similar spike during the same time frames. Historically, rain events cause E. coli levels to rise in the short-term following the event due to several factors before returning to baseline levels shortly after. E. coli sampling results collected on March 27 from White Rock Creek at Mockingbird Lane (299 MPN), Bath House (158 MPN) and White Rock Pump Station (109 MPN) sites all revealed that levels had returned close to their baseline levels.

DWU continued to take water samples through Friday, March 29, to ensure the lake levels remain within normal limits. As a reminder, rainfall can introduce pollutants, including bacteria, into the lake. 

Over the past decade, DWU has been conducting bioassessment and sampling sites along White Rock Creek north of the lake have exhibited levels of E. coli with a geomean of 329 MPN, while those around the lake have shown a geomean of 210 MPN. These numbers are considered the baseline levels of E. coli for the locations. These samples were collected during dry conditions at least seventy-two hours after any rain event and analyzed by a NELAP (National Environmental Laboratory Accreditation Program) accredited laboratory.  

When examining sampling data collected during rain events over the same timespan from local wet weather sites, including the same Mockingbird Lane at White Rock Creek site where White Rock Creek enters White Rock Lake, the geomean from these sampling events is much higher with a geomean of 1094 MPN. These samples were also analyzed by a NELAP accredited laboratory. Notably, these sites often encounter E. coli loads exceeding 2419.6 MPN, the highest amount the laboratory can detect for E. coli. 

Parks officials closed the lake on March 19 for water activities. Elevated bacterial levels were detected due to a recent sewage overflow in Plano that impacted White Rock Creek and the lake.