San Diego Airport & Modular Wetlands System Linear
“Every Space Counts”

Modular Wetlands System Linear – 12 Vault Type Units / Parking Lot Application

The Situation
San Diego development has been in expansion mode the last four years, with the construction industry up nearly 9% from 2013 to 2014. The region is strengthening its economy and infrastructure, preparing for continued global economic activity.

“San Diego International Airport’s expansion program, dubbed “The Green Build”, is expected to help the airport meet current and future travel demands. [It] is the busiest single-runway commercial airport in the United States and the second-busiest single-use runway in the world after London Gatwick with about 465 scheduled operations carrying 48,000 passengers each day.”

Greater San Diego traffic means significant development and the new construction upgrades to the airport has been a pivotal piece to the area’s ability to sustain momentum. Planning was highly publicized and the new San Diego International Airport was designed to be a model of modern design and operation, acting as a symbol of sustainability.

Environmental awareness and understanding went into every structure and square foot of the expanded Terminal 2 and surrounding developments (support sites). notes, “the airport is responsible for administering approximately 661 acres of public lands on the shore of San Diego Bay”. Spaces are systematically designed to accommodate traffic and congestion, while providing valuable revenue streams. One site in particular, the “San Park II” along Pacific Coast Highway (PCH), is a 16 acre parking facility now contributing 2003 parking spaces of the San Diego International Airport’s 6205 total public inventory.

The Challenge
Large-scale parking projects can equate to large-scale challenges – particularly in San Diego. With every parking space comes (x) amounts of polluted stormwater runoff, but also (x) dollars in revenue generation. Parking lots for the San Diego Airport Authority are projected to bring “$35 million dollars in revenue in 2015, partly due to increased enplanements.”² Airport parking lots, in particular, are designed to maximize space and accommodate the flow of transferring passengers, but the obligation for stormwater can pose challenges or threaten the architectural design.

“The Storm Water Management Plan is a major element of the Airport’s commitment to preventing, eliminating, and reducing the discharge of polluted storm water into the surrounding environment and San Diego Bay. The Storm Water Management Plan is designed to control the pollutants generated by everyday operation of the airport, including: trash, litter and debris; petroleum products that might leak from aircraft and motor vehicles; heavy metals potentially contained in the dust from brake pads, rubber tires, engine exhaust; and the fertilizers and pesticides used to maintain the airport’s landscape and facilities.”

The San Park II drainage design called for several grate inlets to be installed throughout the parking lot to intercept runoff in the driving aisles. The site is very flat and grate inlets had to be over sized to prevent ponding during large rain events – a potential safety issue.

“The circumstances are very challenging”, states Zach Kent, lead stormwater engineer for Modular Wetlands. He continues, “The drainage couldn’t be designed as an obstacle to customers getting to their cars in the rain. So, runoff had to drain to the middle of the drive aisles.” This eliminated the opportunity to convey the ‘first flush’ to a landscaped area; essential in traditional LID-type [Low Impact Development] design. “We would have had to put gutters in pedestrian walkways.” Ponding in the landscape areas was also a concern. “If it backed up into the parking lot there would be serious safety issues. Runoff had to be efficiently and quickly conveyed to the storm drain system”.

San Park II encompasses a large space and incorporates designed landscaping, but all of that faced reexamination. From grand palm trees to essential light posts, all were potential losses unless accommodations could be made to avoid the large planter areas and footings – it all had to remain in place. Alternatively, if you were to confiscate parking spaces, the long-term operations would face a number of adverse effects and loss of revenue. Less parking simply meant far less revenue.

The Solution
Modular Wetlands Systems is a San Diego County based stormwater system manufacturer who has supplied thousands of systems to Southern California in the last 10 years (92 in San Diego County alone).

“We knew from experience that all of the pieces could be placed successfully, because the [Modular Wetlands System Linear (MWS Linear)] had done it before and this was our chance to prove it again on a big stage. We are very excited it contributed to the airport project’s success”, says Greg Kent, President of Modular Wetlands. “Our system’s presence alone ensures long term protection of the San Diego Bay, long-term low maintenance costs for the San Diego Airport Authority, and more convenience for the everyday traveler”.

Every developer in San Diego County understands the importance of saving space and the demands for efficiency. The Modular Wetlands System Linear (MWS Linear) appears to be a true standard for San Diego, treating pollutants at a higher level than bioretention, and always capable of maximizing space; especially on high traffic sites with extraordinary real estate valuations.

As the only horizontal flow biofilter in the world, the MWS Linear, becomes an invaluable solution – treating more water in a smaller footprint; more treatment surface area in less space. Modular Wetlands’ MWS Linear has a number of configurations to choose from. The designers and Modular Wetlands’ in-house engineers and advisors worked together to apply the best fit for the parking lot’s needs.

Roger Chung, Project Manager for VA Consulting commented, “John Hayden and their team of engineers worked closely with us. They supplied and worked through multiple options until we were able to design the most applicable combination and solution. The MWS Linear made it very convenient given the obstacles.”

The solution had to be versatile. The horizontal flow vault-type MWS Linear could receive flow (pipe-in) from catch basins, but most importantly, be placed at traffic grade posing zero impact to the parking lot surface design. The MWS Linear is a subsurface flow wetland, with applications that sacrifice no surface space. No impact to parking operations. Virtually unrecognizable.

Modular Wetlands also offers a unique product called the DVERT trough. The DVERT trough was installed inside the standard grate inlet (directly under the grate) and diverts the ‘first flush’ from the basin to the adjacent MWS Linear via pipe – giving designers a more effective way to treat runoff without sacrificing the efficiency of the storm drain design. Zach Kent notes, “Safety is a leading concern and the MWS Linear DVERT facilitated a high level of safety while effectively meeting stormwater treatment requirements.” What’s more, the MWS Linear is a self-contained 3-stage system. Pretreatment does the heavy lifting – collecting trash, debris and sediment giving maintenance crews a focused and easily accessible location for collection and cleanings. When maintained properly the main biofiltration chamber could see years before requiring any attention.

The Result
The San Park II, sixteen acre parking facility, could have turned out much differently. Traditional Low Impact Development (LID) stormwater treatment would have required over a half acre of valuable land, negatively effecting site design. Also, recent studies have shown that some of these LID solutions, such as bioretention, contain organics. The studies further show that organic media can actually have adverse effects on the very water they are meant to treat. A Washington State news release made general observations where phosphorus and dissolved copper increased significantly with short-term significant increases in nitrate. The twelve MWS Linear vault type units at San Park II contain no organic media. No Modular Wetland system does.

In addition, the MWS Linear is the only biofiltration system that can be placed underground and without vegetation. Important, because the handful of available parking lot islands didn’t offer enough room to integrate stormwater Best Management Practices (BMPs). Now, due to the MWS Linear’s full traffic rated concrete top, the units are installed directly under pavement adjacent to the grate inlets; making design simple and efficient.

Every space counts and the result for the San Diego Airport Authority, and community, is sustainability and a substantial return on investment. San Diego International Airport’s parking is a multi-million dollar revenue stream projected to bring $35 million in 2015. The table illustrates just how financially potent a single MWS Linear system can be versus bioretention (non-proprietary BMPs).

Non-Proprietary Bioretention
Quantity of Systems Needed To Treat Site Run-Off 12 Systems12 Systems
Land Lost Per Unit0 Square Feet21,384 Square Feet = 132 Parking Spaces
Property Revenue Lost Annually$0.00$818,000 / Year
Real Estate Value Spent$0.00$4,276,000
Annual Maintenance$9,900$16,800 / Year