By Mindy Bryngelson, P.E.
As the famous line from Kermit the Frog states, it’s not easy being green. While this song was discussing a very different subject, many green initiatives (when it comes to civil engineering, that is) are typically more costly, as contractors are afraid of the “unknown” and may attach higher dollar amounts to projects they have never done before. Typically, the costs in green initiatives on individual sites are not in the materials, but the labor, as they are often done with manpower vs. machine and require a little extra care on the jobsite. However, the more cities and developers embrace these small changes in design and storm water management, the more common they become and the larger impact they have on our overall environment.
There has been a shift in some of these mindsets over the last 20 or so years, primarily driven by the adoption of more stringent storm water standards, which have then also been adopted by jurisdictions having authority. The use of a variety of green initiatives on a site, also referred as a treatment chain, has proven to reduce storm runoff, peak flows rates, and pollutants from entering our streams and rivers.
The easiest and most cost-effective way to implement green design is during the creation of a new development or a larger scale redevelopment.
The more you can remove storm water flow from gutters and pipes and “disconnect” flow, the easier it is to manage storm water quantity and quality. This means setting aside more land to accommodate flows and storage, but on the flipside, it cuts costs on storm sewer structures and piping. This may mean that a subdivision developer will lose 1-2 lots that they traditionally would have sold due to wider ROW (right of way), flowage easement, and ponding areas. However, the costs of damage claims from areas that lack overland flow paths during heavy storms quickly outweigh those lost “benefits.”
Cost-friendly green initiatives
- Native Seeding – the deep root structures of these plants soak up excess water and hold soil in place compared to turf grass. They also are more suited to withstand drought and flooding and do not require the use of chemicals to look great. Low growing turf varieties are available for the Iowa landscape. Visit plantiowanatives.com for more information.
- Compost Amended Soil (Soil Quality Restoration) – Mixing compost into the topsoil prior to seeding restores the organic matter to the soil resulting in increased infiltration and food for new seed. Existing lawns can also be aerated and treated with a thin layer of compost. Some jurisdictions offer rebates. Visit https://www.prrcd.org/watershed_waterways/soil-as-sponges/ for more information.
- Rain Barrels – Capturing building roof drains into barrels allows you to reuse clean rain water around the lawn. The more properties using this BMP, the larger the impact. Some jurisdictions offer rebates. Visit https://www.iowadnr.gov/About-DNR/DNR-News-Releases/ArticleID/150/How-to-Build-Your-Own-Rain-Barrel-Step-by-Step for an individual home owner’s DIY option.
- Rain Garden – If you have soils that percolate well, installing a rain garden to capture roof drains is a great way to encourage infiltration and reduce runoff from your home. Check out the Iowa Rain Garden Design and Installation Manual here: https://www.iowaagriculture.gov/press/pdfs/RainGardenManual.pdf
- Detention Ponds – Ponds can be wet or dry. Either way, properly sized and maintained ponds provide storage during large rain events and allow pollutants to settle out before discharging water. Often the costs of construction are offset by costs of hauling in needed fill dirt to a site. The use of native filter strips around the edges enhance pollutant removal and provide structure to surrounding soils to prevent edge eroding. Native plants that allow water inundation are best suited in dry ponds versus mowed turf grass or concrete channels. The Iowa Storm Water Management Manual provides design standards for these type of detention practices.
- Infiltration Trenches and Basins – Rock-filled trenches and basins encourage infiltration into well-draining underlying soils to reduce runoff. Property sized systems are critical to avoid maintenance issues. These function best in areas protected from compaction by heavy construction traffic.
- This engineered cell uses a combination of rock, soil mix, plants, and tile to store and treat storm water runoff from impervious areas. Costs of these systems are highly dependent upon the availability of the soil materials and tile outlet opportunities. Check out https://www.cleanwateriowa.org/bioretention-cell for more information.
Bioretention Cell – There are a lot of clay soils in Iowa, making infiltration difficult. An alternative to a rain garden is a bioretention cell.
Higher cost green initiatives
- Underground stormwater storage and treatment facilities – Sometimes there isn’t enough room on site for a pond, especially on redeveloped sites. An alternative is to place a system below the parking lot to store water. These systems often encourage infiltration and provide treatment of smaller storm events.
- Rain Water Harvesting/Cisterns (for non-potable building uses) – This is the more elaborate version of rain barrels that requires approval from the jurisdiction’s adopted plumbing code. Rain water can be used for irrigation, flushing toilets, and laundry. Check out https://www.cleanwateriowa.org/rain-water-harvesting
- Pervious pavement systems – These systems can be pavers with special bedding and joint filling rock or even those that allow grass to grow through them! These are great for overflow parking areas and fire truck access roads around sites. You can’t even tell they’re there!
- Porous pavement – Special concrete and asphalt mixes can be installed using special construction techniques that allow water to flow infiltrate the pavement. The finished surface on these systems look different than traditional pavement. These are best used in areas with few vehicle turning movements as the rotating tires can knock the surfacing loose.
- Green Roofs – Why not incorporate a roof top garden into your project? The systems do require review by a structural engineer and are easier to incorporate into new buildings than to retrofit an existing structure. However, new systems are lighter weight and easier to maintain.
As you can see, there are a variety of ways to incorporate environmentally-friendly concepts into your design. Whether you choose from the list of low-cost options or if the sky is the limit, if you involve your civil engineer right from the start and discuss goals and budget, your site can easily include GREEN initiatives!