Houston Public Works Makes Improvements to Critical Groundwater Facility (Source: Spring 2021 Texas APWA Participant)

By Melissa Mack and Tina Yao

Over the past decades, Houston Public Works has been making improvements at 80 of the city’s existing groundwater facilities and six re-pump stations. Originally, some of these groundwater facilities, constructed decades ago, were operated by Municipal Utility Districts. Later, ownership and operations of these facilities were transferred to the City of Houston. The improvements to these facilities, which produce more than 200 million gallons of water a day (MGD), have helped the City meet its customers’ water demands and provide redundancy for its surface water supplies.

Currently, there are more than 20 on-going Capital Improvement Projects (CIP) for groundwater facilities and re-pump stations city-wide. One of the projects in the ongoing CIP is the District 71 groundwater facility improvements in west Houston. This facility, which supplies 5.8 MGD of groundwater, pumps into a neighborhood that also receives treated surface water. District 71 currently uses free chlorine from chlorine gas injection to disinfect the water and provide the required chlorine residual in the distribution system. The water produced from District 71 mixes with chloraminated water in the distribution system.

To avoid water quality issues in the distribution system, Houston Public Works decided to convert the facility’s chlorine disinfection process to a chloramine disinfection process. This required the installation of an ammonia solution feed facility consisting of a new building, bulk storage tank, day tanks, liquid ammonia sulfate (LAS) vacuum feed system, piping, and monitoring and control equipment. Other improvements to the District 71 facility included rehabilitation of existing booster pumps, discharge header modifications (addition of isolation butterfly valves and flow meters), addition of flow meters on well discharge piping, and SCADA modifications to meet current City standards.

“District 71 is the largest groundwater facility in the western part of the city,” said Sandeep Aggarwal, P.E., managing engineer at Houston Water – Drinking Water Operations Branch. “So, this is a critical project for us.”

In 2015, Houston Public Works hired Lockwood, Andrews & Newnam, Inc. (LAN), a national planning, engineering and program management firm, to design these improvements. In November 2018, LEM Construction Co, Inc. began construction on this project.