Harris County MUD 118 is a fully developed district that has been managed by EHRA Engineering for more than 20 years, with most of its infrastructure dating back to the 1970s. In 2003, the district joined the City of Houston’s Groundwater Reduction Plan (GRP), a long-term initiative aimed at addressing land subsidence caused by excessive groundwater pumping. Through this agreement, HCMUD 118 committed to gradually transitioning the primary source of water from groundwater wells to surface water, with the goal of reducing groundwater usage to 20% by the year 2030. This partnership with the City of Houston supports the region’s broader effort to preserve groundwater resources and maintain long-term sustainability.
To provide some background, the City of Houston and surrounding jurisdictions entered into agreements with multiple municipal utility districts (MUDs) to combat severe ground subsidence and comply with the requirements of the Harris-Galveston Subsidence District (HGSD). Established in 1975, HGSD was created to regulate groundwater withdrawal within Harris and Galveston counties and to mitigate the long-term impacts of land subsidence. According to the U.S. Geological Survey (USGS) report “Ground-Water Withdrawals and Land-Surface Subsidence in the Houston-Galveston Region, Texas, 1906–80” published in 1982, excessive groundwater extraction across the region caused water-level declines of 250 to 300 feet in several aquifers. The declines in water levels have caused significant subsidence of the land surface. This results in regional efforts to transition from groundwater to surface water sources and promote sustainable water management practices.
A recent study conducted by the University of Houston analyzed data from 2016 to 2020 across suburban areas, including MUD districts such as HCMUD 118. Using satellite observations, researchers identified land subsidence of up to 3.5 inches in areas north, northwest and west of Houston. During that period, an average rate of approximately 0.8 inches per year was registered. The study concluded that Houston continues to experience one of the fastest rates of subsidence in the Northern Gulf of Mexico region.
As the Water Supply and Groundwater Reduction Plan Wholesale Agreement reaches its implementation phase, HCMUD 118 is now required to begin incorporating surface water into its system and limit groundwater pumping by 2026. EHRA, serving as the district’s engineer, is leading the design and construction of the new infrastructure needed to connect to the existing City of Houston surface water infrastructure, ensuring a reliable, clean and sustainable water source for the community.
The design process began with identifying the nearest City of Houston (COH) waterline infrastructure to the district boundary. Through detailed research and coordination, a potential connection point was located approximately 2,000 linear feet from the district boundary and about 1.2 miles from the district’s Water Plant facility. A feasibility study was then conducted in collaboration with City of Houston engineers to confirm the suitability of this point for surface water delivery.
Based on the confirmed connection, the proposed 1.2-mile waterline alignment will extend along two major roadways: West Montgomery Road, which has a variable right-of-way of approximately 88 feet, and West Mount Houston Road, with a 100-foot right-of-way. Previously, both corridors underwent roadway expansions leaving very limited space for new utilities, at times narrowing the available utility easement to as little as nine feet on each side.
Following an effort to gather existing utility data through open records requests from both the County and the City, the project’s main challenge emerged: design a 12-inch waterline, considering only trenchless construction methods to avoid interference with existing underground infrastructure. Another key design consideration involved the placement of the water meter. Due to space constraints at the connection point, the design team proposed locating the meter station within the district’s remote well site, one of its existing facilities located at the borderline of the district, requiring additional engineering coordination and design refinement.
The project was a collaborative effort between EHRA’s District Services and Water and Wastewater Management (W&WWM) Departments. W&WWM was responsible for designing the Liquid Ammonium Sulfate (LAS) disinfection system and performing the chemical dosage calculations required to properly blend the surface water with the existing groundwater sources at the water plant. Meanwhile, the District Services team led the design of the waterline extension and coordinated the necessary agreements with the City of Houston to facilitate the connection and delivery of surface water.
At EHRA, we take pride in designing solutions that minimize disruption to public infrastructure and community life. As the district’s engineers, our top priority is to ensure both functionality and the comfort of the residents we serve.
The project is currently under final review for contract approval regarding maintenance and water distribution agreements, with construction anticipated to begin in early 2026.
