More Than Just Parking: A Watershed Moment in Grapevine

In Grapevine, Texas, a small parking lot renovation at the local botanical gardens could be the impetus for big-time municipal changes.

The Grapevine Botanical Gardens at Heritage Park is home to meandering trails, streams, ponds and hundreds of plant varieties; it’s freely accessible to the public and open 365 days a year. The property includes a longstanding structure, the Bessie Mitchell House, which is part of the land acquired from the Mitchell family in 1995 and is currently under renovation.

The renovation includes a parking lot expansion, which provided an opportunity to responsibly manage stormwater runoff utilizing green infrastructure strategies as well as mitigate significant erosion occurring along Morehead Branch, a creek adjacent to the site.

Familiar with TBG from ongoing work at nearby Denton Creek Park, the City of Grapevine Parks and Recreation Department commissioned TBG to redesign the parking lot to add additional spaces and realize the desired stormwater management objectives.

The project has provided an exciting opportunity to explore a variety of stormwater management approaches, add new educational aspects to the botanical gardens, and support the City in its mission to incorporate green infrastructure approaches in a setting as common and ubiquitous as a parking lot.

Early in the process, key performance factors were identified through collaborative efforts between TBG and the City. Socially, the team wanted to provide educational learning opportunities for green infrastructure strategies. Environmental goals included mitigating bank erosion by slowing and cleansing stormwater runoff before entering into the creek system. Economically, the team strategically chose green infrastructure systems for long-term cost savings, showcasing financial benefits over the long haul.

Site analysis was conducted to understand the flow of water on site and how much stormwater flows off site to set baseline metrics. The team then studied varieties of stormwater percolation, filtration and collection systems, gauging their effectiveness based on considerations like functionality, cost and maintenance needs. The systems studied included pervious concrete, permeable concrete pavers, geogrid with aggregate base, bioswale infiltration systems, bioretention areas and vegetated filter strips.

Ultimately, multiple green infrastructure systems were strategically chosen and designed together to meet the team’s design goals, and nearly every type of system studied was integrated into the design solution. Most of the parking spots were kept in their current configuration, while another bank of parking was added as well as a new drop-off area, and several medians were repurposed as rain gardens.

The new parking area is comprised of decomposed granite with the geogrid sub base that allows percolation, while the handicapped parking spots and pedestrian pathways are constructed of porous pavers, which provide a more durable quality that will better accommodate wheelchairs.

The parking lot’s existing storm inlet was kept in place, but it will be bounded by rain gardens on both sides, and a bioswale near the main entry will be a centrally positioned focal point. Finally, vegetated filter strips are featured along the street, showcasing a wide variety of stormwater management systems, which are explained through the inclusion of educational signage. The selection of an ecologically inspired plant palette will further assist with the project’s environmental ethos.

Installation of the project is underway and it has been a valuable learning opportunity for both TBG and the City of Grapevine. The City views it as a pilot project and hopes to one day revise the municipal development code to incentivize or require better-performing parking lots of this nature.