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The rapid pace of change seems to affect everything in the engineering and construction world, even something as established as parking lots. First, let’s talk about design methods.
When I started doing retail/commercial site design 20 years ago, configuring a parking lot was a hit or miss process that involved analyzing multiple stall, aisle, and angle options in an effort to meet the client’s required stall count while complying with local zoning requirements. Once you developed a layout that met the numbers you needed, it was time to work around any stormwater and grading constraints that the site might offer, which may or may not require you to change your original layout.
Recently, AutoCAD introduced add-ons that allowed a designer to input all design variables such as stall size, angles, aisle widths, direction of travel, and boundary constraints. With a few clicks of the mouse, you could see several design options and stall counts. Now we’ve progressed to the point where our design software not only allows us to optimize our parking stall layout, but at the same time it can create preliminary grading and stormwater plans and estimate the cost for the site work.
All of these improvements allow our designers and engineers to look at more options than we ever could before at a much earlier point in the design process. We are also able to get a good idea of how the construction cost is impacted by each design change we make, so we are able to determine the most efficient design for a specific site. The result is that we are able to create sustainable, long-term solutions for our clients and move projects more quickly through the approval process.
Looking at the details of design, we are seeing a number of trends. Stormwater management continues to drive design in many ways. In most cases, gone are the days of supersized parking lots draining to massive detention basins. To meet current regulations, it’s necessary to deal with stormwater on a much smaller scale. Landscaped islands are becoming more important, not only because they are aesthetically pleasing, but because they reduce thermal impacts and can be designed as rain gardens to manage stormwater.
Stormwater volume is being reduced through infiltration in bioretention swales that often become a feature of the parking lot. The large, centralized stormwater basins are being split up and spread throughout the site to deal with runoff more directly. Stormwater runoff volume is being reduced through infiltration in lawn areas, subsurface chambers, and through pervious pavement. The popular LEED© certification system rewards many of these approaches.
About 5-10 years ago, we saw larger retailers trying to reduce site construction costs by minimizing the amount of pavement they placed in their parking lots and trying to limit heavier vehicles to certain sections of the parking lot. In the northeast, we have started to see some of these pavement structures start to deteriorate from freeze/thaw cycles and vehicular traffic. As a result, we are beginning to see a trend back to heavier, more traditional pavement structures.
They say the only thing constant is change. This is certainly true in the engineering industry. I think that’s why I enjoy it so much.