About the author: Abigail Stanhouse, P.E., is an engineer for Lockwood, Andrews & Newnam Inc. Stanhouse can be reached at [email protected].
A golf course built more than 50 years ago has become the solution for flooding and drainage issues for the Clear Lake City Water Authority (CLCWA) in Houston.
Developed in the 1960s, the 178-acre golf course was a popular community amenity. The property is located between multiple subdivisions and is lined by residences. Even after the golf course closed, the residents continue to use the old golf cart paths for walking and jogging.
In 2005, when the owner decided to sell the property, local developers expressed interest in turning the golf course into a massive commercial development. With the community already experiencing drainage issues due to increased runoff from growth and development over the previous decades, drainage control was a high priority in the area, so residents approached the CLCWA, the local provider of water, sewage and drainage services. After hearing their concerns, in 2011, CLCWA purchased the golf course for $6.2 million and decided to convert it into a series of detention ponds to improve storm water management in the area.
"When the water authority was originally developed, they didn’t have a detention policy, and the drainage did not keep up with the growth,” said Jennifer Morrow, CLCWA’s general manager. “This former golf course was the perfect chance to retrofit our master-planned community for more detention volume.”
CLCWA board members also saw the property as an opportunity to develop the massive green space so that it continued to provide recreational benefits to the surrounding community. With the community’s input, Houston-based SWA Architects created a master plan in 2013 to redevelop the former golf course.
New Beginnings
The project, named Exploration Green in honor of the community’s local exploration legacy and its proximity to Johnson Space Center, features a series of lake-like detention ponds, abundant natural habitat with wetlands and native grass land areas, as well as hike-and-bike trails, athletic fields and other amenities. In December 2013, local residents and CLCWA partnered to create a nonprofit organization called the Exploration Green Conservancy Inc. to develop, preserve and protect the project’s green spaces. CLCWA hired Lockwood, Andrews & Newnam Inc. (LAN) to prepare construction documents and oversee the construction of the Exploration Green detention facility. In September 2014, CLCWA signed a conservation easement agreement with the Galveston Bay Foundation to ensure the property would remain a green space forever.
Exploration Green will plant more than 60 different varieties of trees to accommodate floodings and drought, as well as nurture local wildlife.
Detention Ponds
In 2016, voters approved an $88 million bond, where $28 million was allocated to the construction of the Exploration Green detention facility. The project comprises five detention ponds, each incorporated with green spaces. Each pond will be constructed in phases, with the project having a total of five phases. The first phase is currently under construction.
The detention ponds, which are designed for 100-year storm events, are linked to each other and have been arranged in the master plan to have storage capacities ranging from 260 to 442 acre-ft. Each pond will have a 6-ft-deep permanent pool with the ability to detain significant amounts of storm water from local streets, property and waterways within the drainage area. As a flood threat eases, the ponds slowly release detained storm water, ultimately decreasing flooding. Per the master plan, the Exploration Green detention facility will have a storage capacity of 1,680 acre-ft—the equivalent of 750 Olympic-sized swimming pools.
“While the masterplan gave us a basic layout, as design progressed, we had to make a number of modifications,” said Kelly Shipley, project manager for LAN. “We collaborated with various groups to incorporate as much green space as possible, while satisfying CLCWA’s primary objective, which is to maximize the authority’s detention capacity. We also addressed concerns related to the ponds’ aesthetics and their proximity to residential homes. It was a delicate balancing act.”
The project also requires excavation to construct these detention ponds. Based on master plan layouts, it is estimated the entire project will require more than 2 million cu yd of excavation. To date, the general contractors for Phase 1, LECON Inc. and Paskey Inc., have excavated approximately 340,000 cu yd of soil. LECON performed the majority of the excavation and installed an irrigation line and piping for a planned aeration system. Paskey installed the Phase 1 detention pond outfall structure and excavated more than 30,000 cu yd of soil.
Building the detention ponds already has turned out to be immensely beneficial to the CLCWA. In August 2017, Hurricane Harvey dumped an estimated 40 in. of rainfall on the Clear Lake area and even more in some surrounding neighborhoods. Although only 80% of the Phase 1 pond was excavated at the time of Hurricane Harvey, the detention pond protected an estimated 150 houses from flooding. When all five phases are constructed, the entire detention facility is estimated to protect 2,000 to 3,000 homes near the floodplain by Horsepen Bayou.
One detention pond protected an estimated 150 homes from flooding during Hurricane Harvey.
Natural Habitat & Recreation
In addition to controlling flooding, the Exploration Green detention facility will provide green spaces. Once complete, the project will feature 101 acres of upland or island habitat and 39 acres of wetlands. To help with this effort, CLCWA and the conservancy collaborated and formed partnerships with a number of organizations, including the Galveston Bay Foundation, Trees for Houston, Texas A&M’s Texas Coastal Watershed and Agrilife Extension Programs, and the Stormwater Wetland Program.
As storm water runoff is conveyed through the property from neighborhoods within the drainage area, the wetlands will naturally filter the water as it flows in tributary streams to Horsepen Bayou, Armand Bayou and on to Galveston Bay. The wetlands also will reduce mosquitoes in the constantly flowing water.
In addition, the conservancy is working with hundreds of volunteers in the Clear Lake community to plant native trees, shrubs, grasses and flowers that will draw a variety of wildlife to the area.
Over the last year, the conservancy has planted more than 300 native trees within the Phase 1 project area, with 700 more to be planted in the next few months. At completion, Exploration Green will include more than 60 different varieties of trees. The expanded diversity of native flora will better accommodate flooding and droughts, while also providing food and nectar for birds, butterflies and wildlife. Lastly, the natural habitat will be complemented by an entrance plaza with a brook, approximately 12 miles of hike-and-bike trails, multi-use athletic fields, leisure and relaxation areas, and scenic lookouts.
“This park will be a diamond in the heart of the Clear Lake community,” said Doug Peterson, vice chair of the Exploration Green Conservancy. “To have such a huge green space in the middle of a highly populated area is something that this community can look upon with a lot of pride.”
Onward
Originally envisioned as a 15-year effort, the project has been accelerated to be completed in five years. The first phase is scheduled for completion in December 2017.
“Cities have been using athletic fields and parks for years when planning community amenities,” Morrow said. “Looking at ways to turn green spaces into detention can not only mitigate the impact of extreme storm events, but also serve as a multipurpose community benefit.”
