High contaminant average prompts letter to San Marcos water customers

FILE IMAGE (David Yeomans/KXAN)
FILE IMAGE (David Yeomans/KXAN)

SAN MARCOS, Texas (KXAN) — People living in San Marcos are receiving another notice about high averages of a disinfection byproduct in the water system associated with the Halloween floods last fall.

The city’s water supply in sampled in eight separate locations four times throughout the year and the results are averaged over the previous four quarters.

“The San Marcos water supply continues to be high quality and safe to drink,” said Tom Taggart, executive director of public services. “Total trihalomethane levels in the water system continue to remain well below the maximum contaminant level. However due to the effect of averaging the last four quarters, one site remains slightly out of compliance.”

Trihalomethane is an organic compound formed when organic materials combine over time with chlorine used to disinfect drinking water.

Samples taken on Nov. 7, 2013 at a site near 345 Champions Blvd. showed trihalomethane levels stood at 158 parts per billion (ppb). The federal standard average is 80 ppb. Several followup tests showed numbers well below those limits. However, the reading after the flood boosted the average numbers to 87 ppb in the 4th quarter of 2013, 86 ppb for the 1st quarter of 2014, and 81 ppb for the 2nd quarter of 2014. The latest number prompted the Texas Commission on Environmental Quality to require the City of San Marcos to send out another notice to its customers.

The city said it sent required notices to customers in their utility bills in early June and will mail a new letter to city water customers by Tuesday, July 29.

More than 15 inches of rain fell within 24 hours on Oct. 31, 2013, causing flooding in the Guadalupe River watershed. San Marcos receives 93 percent of its water supply from the Canyon Lake area and 7 percent from the Edwards Aquifer.

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