Sustainable Sites Initiative

Queuing Garden for the Florida Aquarium

Florida Aquarium Parking Lot and Queuing Garden

Size & Type of Project:
11.5 acres; Urban redevelopment; Greyfield

Location:
Tampa, Florida

Budget:
$1,091,000 for base sustainable construction cost/ $2,124,500 with enhancements and research/education components

Project Phase:

Completed 1995

Project Overview

In 1993, Florida Aquarium in mid-town Tampa partnered with the Southwest Florida Water Management District to build an 11.25- acre stormwater research and demonstration area to evaluate the effectiveness of alternative low impact parking lot design to reduce runoff and improve the quality of water flowing into Tampa Bay, an Estuary of National Significance included in the National Estuary Program. This partnership was significant, given that all parties were aware from the outset that approximately one-third of the parking lot area would be eventually removed and redeveloped for a cruise ship terminal.

The fundamental goal of the project was to extend the environmental education objectives of the Aquarium to the parking lot and the Aquarium's shaded Queuing Garden near the entrance. The Aquarium uses its entire site to tell Florida's unique water story by following a drop of water from its underground source to the open sea.

The original site plan for the parking lot area was not envisioned as sustainable, however the project team worked closely with Florida Aquarium to develop an alternative site plan that would demonstrate the benefits of sustainable practices. In the new plan, the site was configured to maximize the use of green space vegetated with native plants to convey, infiltrate, and filter stormwater runoff.

During a two-year period, more than 50 storm events were sampled to measure water quality and quantity from eight small basins in the parking lot. The study greatly improved the scientific knowledge base for sustainable development practice, specifically demonstrating the benefits of low impact development strategies while educating Aquarium visitors and employees in the process. Regulatory agencies are now working to incorporate some of these elements into a proposed forward-thinking stormwater regulation for the State of Florida - the Unified Stormwater Treatment Rule.

Site Context

Tampa sits in the Southwestern Coastal Plain (Southwestern Florida Flatwoods) ecoregion. In this humid subtropical climate, Tampa receives an annual precipitation of 46.3 inches, occurring primarily during the summer rainy season. The average high temperature is 82 degrees and the average low temperature is 65 degrees (Fahrenheit).
Florida Aquarium is an urban redevelopment site, built on a former Coca Cola bottling facility. Situated in downtown Tampa, on the waterfront next to the Ybor Channel, the Florida Aquarium site is near entertainment venues, restaurants and shops and draws many visitors. The study area is an 11.25 acre parking lot that currently serves approximately 700,000 visitors annually.

Site Plan

Sustainable Practices

Stormwater Treatment:  The 11.25-acre parking lot was the study site for the low-impact stormwater treatment system. The research was designed to determine pollutant load reductions measured from three elements in the treatment train: different treatment types in the parking lot, a planted strand with native wetland trees, and a small pond used for final treatment (See Figure). Additionally, the Queuing Garden near the entrance of the Aquarium treated stormwater runoff but it did not drain into the parking lot system; rather it was a pretreatment system for runoff that flowed directly into the parking lot pond.

In the study site, stormwater runoff was directed from the Aquarium roof and parking lot into a chain of bioswales, into smaller basins that converge into larger ones (i.e. strands), and finally, through a linear progression of vegetated filtering zones. The strands fed the parking lot pond before the pond discharged to the Ybor Channel. Runoff from the pedestrian areas is also redirected to help support vegetated areas.  

• Stormwater treatment train - a series of increasingly larger cells (i.e. bioswales, strands) for filtration, infiltration and sedimentation prior to discharge
• Bioswales - vegetated open channels or swales that infiltrate and transport runoff water
• Strands - a series, or channel, of wider, deeper vegetated basins that collect runoff after treatment by bioswales. Strands have a longer detention time than bioswales.
• Clarification pond - ponds that supplement storage and pollutant removal

The components of the stormwater treatment train (described above), in addition to permeable paving, were used to work synergistically to accomplish water quality and quantity goals. Today, all bioswales and one strand (adjacent to York Street) exist although the major strand (near Ybor Channel) and parking lot pond were removed for the cruise ship terminal. See the "Monitoring" section below for more details on results.

Pervious pavement: The experimental design in the parking lot allowed for the testing of three paving surfaces as well as vegetated swales (i.e. bioswales) to paved swales or pipes. Three types of paving were compared-asphalt, concrete, and pervious paving. The study was conducted to test the effectiveness of permeable pavers for reducing Total Suspended Solid (TSS), nutrient, metal, and thermal loads. See the "Monitoring" section below for more details on results.

Increased native vegetation cover/ Reduced impervious surfaces: Green space was increased by 10 percent by reducing the dimensions of individual parking spaces by 2 feet. This created more efficient layouts that allowed the incorporation of bioswales without reducing the number of parking spaces. It also did not compromise parking since the design had the front end of vehicles hanging over grass rather than impervious paving. The cost savings in reduced concrete was re-invested in additional native vegetation and trees. The vegetated areas reduced the amount of stormwater runoff from the parking lot.

Integrated Pest Management: The use of native vegetation was helpful in the 90 percent reduction of commonly used fertilizers and pesticides. Chemical treatments were implemented only in situations where a plant's vigor and survival were in danger.

Visitor comfort: The pedestrian plaza near the entrance is designed as a Queuing Garden that provides seasonal shade and seating for waiting visitors. Planters are placed to create a variety of smaller public spaces conducive to interaction or meeting in small groups to plan activities.

Site interpretation: Aquarium visitors receive information about the project and the connection between rain, urban development, and water quality through brochures, signage and at the research station. The brochure gives tips on how residents can prevent pollution on a daily basis. Educational signage is installed to focus the attention of the user on the native habitats and vegetated stormwater catchments. Before its removal (due to the cruise ship terminal), the research station was visited by students and general Aquarium visitors for learning more about the project and stormwater runoff.

Construction Cost

The project team allotted costs for sustainable elements to three categories: base; base + enhancement; base + enhancement + research/education (detailed below). This was important for applicability to other sites as the team continues to promote the idea of sustainable site development to the development community. In other words, evaluating several options for sustainable features and the associated costs determines the level of sustainable design a client is capable of achieving. As noted below, the most fundamental and basic features (see "Sustainable Base cost" below) make the case for supporting sustainable design on a cost-competitive basis when compared to the original budget (without sustainable features) of $1,340,000. A number of enhancements, including those for education, research and demonstration purposes, resulted in additional costs. Those costs are not necessarily needed in pursuing sustainable design as an alternative to conventional approaches.

Due to the program plan for Florida Aquarium (i.e. research and development) and with additional funding from grants, the highest level of sustainable features was implemented (see "Sustainable Base cost + Enhancements + Research/Education" below).

• Sustainable Base cost: site work with stormwater system = $1,091,000
  A direct comparison of infrastructure cost savings of a natural drainage system versus the original pipe/curb/retaining wall intensive plan showed a 19 percent reduction from the original design's budget. Money saved by using less concrete pipe, along with the elimination of curbing and a retaining wall, was re-invested in additional trees and swale plantings and experimental pavement test areas.
• Sustainable Base cost + Enhancements: The sustainable plan with enhanced paving and landscaping = $1,634,000 (This included $275,000 in additional natural system improvements including landscaping, low volume irrigation and shoreline enhancements to Ybor Channel. It also included an additional $268,000 for pervious and concrete paving in the parking area. These features were planned as part of the project, and alternative grant funding was specifically sought.)
• Sustainable Base cost + Enhancements + Research/Education: Enhanced sustainable plan with professional graphics, education boardwalk, research equipment and research station = $2,124,500 (Additional cost for research/education was secured through grants).

Monitoring Information

Southwest Florida Water Management District (SFWMD) measured rainfall and flow from eight of the subcatchments (i.e. test swales) in the parking area and collected water-quality samples in a flow-weighted basis. Researchers collected samples from 59 storm events over a two-year period (1998-2000). The experimental design in the parking lot allowed for the testing of three surfaces as well as basins with vegetated swales and paved swales, creating four treatment types with two replicates of each type. The basins without swales still had depressions similar to the rest of the parking lot, but the depressions were covered over with asphalt. All basins had some landscaped garden areas providing opportunities for runoff to infiltrate. The data allowed comparisons among treatment techniques as well as among paving surfaces. The four treatment types included: (1) asphalt paving with no swale (typical of most parking lots), (2) asphalt paving with a swale, (3) concrete (cement) paving with a swale, and (4) porous (permeable) paving with a swale.

The data included peak runoff rate, runoff volume, runoff co-efficients, and water quality. To determine how these modifications and paving types might change runoff amounts and pollutant concentrations, both water quality and quantity were measured in eight small basins in the parking lot. To evaluate long-term consequences and estimate maintenance requirements, sediment samples from both bioswales and paved swales were collected. To understand conditions that influence pollutant concentrations, rainfall characteristics, vegetated areas and paving types were analyzed. Water quality, sediment samples, and flow measurements were collected in the strand and the wet detention pond to estimate the additional stormwater treatment they provide. Finally the data were evaluated statistically to determine differences between years, differences between basins and relationships between variables.

Overall, monitoring has demonstrated that the sustainable practices significantly reduced runoff volume and protected water quality.  When the volume of water discharged from all the different elements to the treatment train (the swales, the strand, and the pond) were compared, calculations showed that almost all the runoff was retained on site.  Basins paved with porous pavement had the best percent removal of pollution loads, with many removal rates for metals greater than 75 percent in the basin with a smaller garden area and greater than 90 percent with larger gardens. Sediment samples implicated asphalt paving material as a source for metals.  Sediment sampling also identified polycyclic aromatic hydrocarbons (PAHs) approaching significantly toxic levels. Metal and nutrient pollutants in the sediments were not found to be migrating to the deeper strata.  Phosphorus and nitrogen in the sediments increased from year one to year two.  More phosphorus loads were discharged from basins with vegetated swales than from basins with no swales.  Even with some poor removal rates by swales in the parking lot for phosphorus, when the entire system is evaluated, efficiencies are good since the site retained over 99 percent of the storm runoff during the year that it was evaluated. For more details on monitoring data and results, see "Enhanced Parking Lot Design for Stormwater Treatment" by Betty Rushton, Ph.D.  (Proceedings of 9th International Conference on Urban Drainage, September 8-13, 2002 EWRI/IWA/ASCE)

Maintenance

The Florida Aquarium continues to maintain and manage the property as a stormwater filtering landscape. Total landscape maintenance costs were comparable to a conventional landscape. Although there was a 90 percent reduction in commonly used fertilizers and pesticides, the new non-toxic practices required specialized management and increased labor to maintain the facility. Oversight was provided by the owner's staff biologist as an in-house cost. Maintenance and management of paved areas involved no additional costs due date. In theory, pervious paving does need to be vacuumed after a number of years to maintain high effectiveness.

Vegetated swale in parking lot

Issues/Constraints of the Site

• The site contained two pre-existing ponds that met State stormwater regulations. Criteria to meet regulations does not account for the source of the runoff, which in this case, traveled from surrounding roadways and the Aquarium building rooftop, causing extremely high pollutant loadings. The project team had to retrofit these ponds in order to manage runoff and cleanse water properly.
• The site consisted of urban soils of poor quality. The lack of organics and the high pH of the soil dictated the use of species native to coastal areas and those with a successful history of dealing with difficult sites. Soil conditions have improved with the growth of roots and the trapping of detritus in landscape areas.
• The site had to maximize efficiency of parking and user function at the same time that sustainable practices were employed. Reconfiguring green space into swales required a waiver of the city landscape code. The owner partnered with the Southwest Florida Water Management District to incorporate some of the less conventional techniques.
• The basic sustainable site work had to be constructed under the same budget as the original design.
• The Aquarium building was under construction but no site work for the grounds or parking had been started. Due to the late change in site design, the design cost increased and construction had to be moved forward quickly so as not to delay the opening of the Aquarium.

Lessons Learned

• Changing regulations by making parking spaces 0.62 m (2 ft.) shorter provided land for swales without reducing the number of parking spaces. The change also did not compromise parking because the design simply called for the front end of vehicles to overhang grass rather than impermeable paving.
• Because some of the native and appropriate plant species were not commonly used in the landscape, some areas required seasonal management techniques. An ordinary outsourcing of landscape maintenance was difficult. The Aquarium biologist took on the task of managing the grounds, which tended to stretch resources thin in the beginning until the biologist developed strategies to deal with the site.
• During the course of the study, the outfall of the parking lot pond, the terminal pond in the treatment train, was being monitored by equipment which automatically recorded rainfall and discharge events. Discharges are allowable and permitted under current State rules, and runoff is a natural function in non arid climates. Water was discharged only once from the site even with the high precipitation rate. Such infrequent discharges are unusual and the total reduction in loading exceeded the benefit of filtration and sedimentation values.
  The bioswales received no credit from current Flroida stormwater rules requiring treatment of runoff because they were shallower than normally allowed and the water table was higher than what would be required to get credit for infiltration. The study documented the value of extremely shallow swales in high water table conditions to improve infiltration. However, the swales, which were not given stormwater credit on their permit, were highly effective in meeting regulatory pollution control requirements without the need to utilize the balance of the system. Subsequent studies looked at the benefit of retrofits of the pre-existing ponds at the site by incorporating biological assimilation and the treatment train approach.
• This project has opened up opportunities for new approaches to stormwater management in Florida. The project and associated research have also been used by others across the nation to promote sustainable practices. The use of a variety of best management practices has been on visible display to the public. Florida regulatory agencies are now working to incorporate some of these elements in a proposed Unified State Stormwater Rule.
• Some design costs would have been reduced had sustainable practices been in place from the inception of the original site design. For example, approximately $45,000 was spent on new (sustainable) designs which could have been saved if the site plan had been designed, engineered and permitted with sustainable practices in mind.
• Although the initial budget was insufficient to cover all the sustainable practices and research components envisioned, the project team and Florida Aquarium were able to obtain additional funding from grants (U.S. Environmental Protection Agency, the Florida Department of Environmental Protection and the Southwest Florida Water Management District).

More project details

www.nrdc.org/water/pollution/storm/chap12.asp

Project Consultants

Owner/Client
Florida Aquarium

Partners
Tampa Port Authority
City of Tampa

Planner/Landscape Architect
Thomas Levin
President
Ekistics Design Studio, Inc.

Civil Engineer
Paul Skidmore
Vice President
Florida Technical Services, Inc.