BATTENING DOWN THE HATCHES cost of the plastic chambers was less than the CMP. Chambers are relatively inexpensive, but because of their low profile and limited storage capacity, they require a large footprint. When excavation, installation and backfill costs were considered, the corrugated metal pipe solution provided the lowest total cost. The main point here is that owners and developers should always ask for a detailed cost estimate of underground systems options that include excavation, material, installation and backfill costs.
Stormwater systems, commonly referred to as Best Management Practices (BMPs) can be classified as “structural” (devices installed or constructed on a site) or “non-structural” (modified landscaping practices such as rain gardens and swales). Recently, there has been a big push for more non-structural BMPs to be implemented instead of the traditional structural BMPs. There seems to be a perception that these BMPs can be installed and left alone, with very little to no maintenance. That couldn’t be further from the truth. Let’s think about what happens to a non-structural land based system like a bioswale. A rain event occur, and the bioretention system functions as specified. Storm water flows to it from adjacent impervious areas, and slowly infiltrates and evapotranspires, depositing sediment, trash and debris on the surface. As sediment accumulates, the bioswale may no longer provide the design infiltration rate or storage volume. Ponding and flooding occurs, and the appearance of the site deteriorates as trash accumulates and plants grow unchecked. Even ponds need maintenance. Accumulated trash and debris can clog inlet and outlet structures, side slopes can fail, vegetation can grow unchecked. Poor maintenance can result in unpleasant odors, nuisance insects, algae Structural BMP’s often have lower lifecycle costs than non-structural solutions, as pollutants are captured and stored in one central location. blooms and unsightly aesthetics that could Photo credit: Contech® Engineered Solutions LLC. impact property value. Structural BMPs often have lower lifecycle costs than non-structural solutions, Question 3: What are the as pollutants are captured and stored in one lifecycle costs of the stormwater central location. For example, the Filterra® management system? All stormwater management systems will Biofiltration system uses specially engineed maintenance; it’s unavoidable. Trash and neered media and is far more compact than sediment will accumulate, filters will clog and traditional biofiltration. It’s small footprint proper system functionality will be impaired. takes up less land space and maintenance So the question becomes how often will can be done in less than 30 minutes. maintenance be needed, how easy is it to Even though structural BMPs are maintain, how much will it cost, and who will often easier to maintain than non-structural pay for it? In most cases, it’s the owner who’s systems, it’s important to note that mainon the hook. tenance requirements differ considerably In years past, maintenance of stormdepending on the type of product used and water systems was not a major concern, as the manufacturer. there was limited monitoring being done. The main point here is that not all The old adage of “out of sight, out of mind” stormwater systems are the same. Work prevailed. This is no longer the case, as more municipalities are enwith your consulting engineer to fully understand the lifecycle cost forcing maintenance protocols and fining those that fail to maintain of the stormwater management system that is being recommended their stormwater systems. before final selection. During the design phase, many engineers are focused on meeting There is no need to overspend on stormwater management the initial challenge of designing a system that will meet the local stormsolutions. So the next time you embark on a new project, ask your water regulations and getting their permits approved. Lifecycle costs are design team the three questions noted above. It could save you often not a consideration. This is beginning to change. thousands of dollars in the long run. CCR
A typical parking space is 9 feet x 18 feet or 163 square feet. For every 1,000 square feet of developed space, the developer is typically required to have 2.6 parking spots.
David Corr, Sr., is the Director of Corporate Marketing at Contech® Engineered Solutions LLC.
COMMERCIAL CONSTRUCTION & RENOVATION — NOVEMBER : DECEMBER 2018