Another example of how LID adds value involves master planned developments which offer a greater opportunity for large-scale reuse of stormwater by incorporating LID features. The LID systems can treat the runoff, capture the excess water, and then use the captured water to reduce the potable water needed for irrigation and other potential non-potable water uses such cooling tower makeup water. This approach is essential to minimize the environmental impact of the project. City Place, formerly Springwoods Village, in the Houston area employs natural streams, vegetated drainage swales, bioswales, sedimentation basins, and wet ponds to treat stormwater runoff. The treated stormwater is then made available as a non-potable water utility for non-potable demands such as cooling towers and irrigation. By incorporating LID into the overall design and infrastructure systems, master planned communities can create sustainable and efficient non- potable water supply systems that benefit both the environment and community. Captured and reused stormwater can help to alleviate flooding downstream by diverting excess runoff to reduce the demand for potable water treatment and distribution, and to improve the quality of the water released into the downstream systems. Finally, LID can be applied to small-scale development projects in innovative ways as well, despite limited space available to accommodate the features. Midtown Park in Houston is an example of this approach, using linear rain gardens to capture, detain, and treat stormwater runoff. At Midtown Park, an underground tank captures additional runoff, which is then reused for park irrigation. A bioswale provides overflow capacity for further detention and treatment of runoff on-site. The use of LID reduces the need for above ground detention, allowing the space to be repurposed for a revenue-generating parking facility. Reimagining the surface detention area as a LID park feature adds to the enjoyment of the space. “LID was integral in Midtown’s ability to address the dilemma of being ‘under-parked,’” Marshall says. “In the case of Midtown Park, ‘under-parked’ had a dual meaning in that the neighborhood did not have enough park space nor enough parking to meet the demands of its residents and visitors.” The “under-parked” dilemma presented an opportunity to include creative LID elements in the Midtown Park design to provide site detention as a park feature while allowing for the development of a 400-space underground parking facility. According to Marshall, Midtown Park’s signature LID feature is the “bayou” which serves as the site detention system for the project. The “bayou” is a constructed water channel which mimics the natural bayous, swamps, bottomland hardwood forests, and wetlands of Houston. The site’s LID rainwater collection system stores water from the exposed portion of the top of the underground parking garage and other impervious surfaces in the park in a 70,000-gallon subsurface cistern to be reused on-site for irrigating plant material.
“Working together with bioswales and rain gardens, the LID features at Midtown Park have proven to enhance economic and environmental resiliency by protecting against flooding while improving water quality,” Marshall says. “During extreme rainfall events, like Hurricane Harvey, the ‘bayou’ has detained stormwater to prevent local flooding and property damage.” The successful integration of highly complex green stormwater infrastructure systems has helped to offset operational costs and led Midtown Park to become Houston’s first SITES-certified project, a rating system designed to protect ecosystems. LID can also expand to a larger scale with the re-greening and expansion of drainage facilities. This includes the Harris County (Texas) Flood Control District’s Brays Bayou project, which has transformed flood damage reduction projects into multi-use parks and landscapes. Additionally, the Los Angeles River Ecosystem Restoration, which involved restoring 11 miles along the river and includes the reintroduction of ecological and physical processes, such as a more natural hydrologic and hydraulic regime that reconnects the river to historic floodplains and tributaries, reduced flow velocities, increased infiltration, improved natural sediment processes, and improved water quality. Much of the initial attention from infrastructure funding was focused on broadband and electric vehicle deployment. But now, other funding sources are getting lots of attention and bridge repair and replacement is occurring throughout the country. The bipartisan infrastructure bill provided $5 billion per year until 2026 just for bridges. That funding is encouraging state and local officials to reimagine how they deliver bridge projects. In 2021, it was reported that U.S. bridges had accrued a $125 billion backlog of critical maintenance needs. That was because 42 percent of them had been in service for more than 50 years. The same report
26
csengineermag.com
June 2023
Made with FlippingBook Annual report