Constructed Wetlands: Dealing with the Stressors of Modern Society
Ben Lagasse, Abbey Massaro, Alex Mauro
NATSCI 397A Professional Writing
University of Massachusetts Amherst
December 5, 2013
Wetlands at one point covered 220 million acres of the countries landscape (North American Bird Conservation Initiative, 2013, p. 7). This historic base of natural wetlands was relentlessly destroyed in the recent past to make way for commercial development, agricultural development, and construction of infrastructure for a growing country. As the human footprint continues to crawl across the landscape we continue to lose natural wetlands at an alarming rate. It is known that as of 1984, 54% of the countries natural wetlands had been drained or filled for development or agriculture. 2/3 of the countries remaining natural wetlands are privately owned, whether they ultimately end up being preserved or developed is uncertain (North American Bird Conservation Initiative, 2013, p6).
Davis et. al.(2008) define natural wetlands as, “transitional ecosystems that exist at the interface between aquatic and terrestrial systems” (p. 295). Constructed wetlands strive to recreate the benefits and services provided by natural wetlands. These services include flood mitigation and water purification. Constructed wetlands can be used to purify wastewaters from private, agricultural, and urban sources. The creation and maintenance of these wetlands is 50-90% cheaper than traditional methods of water treatment. Wetlands are also the primary provider of breeding and feeding habitat for waterfowl. Having a robust waterfowl population in turn fuels the 2.7 billion dollars of economic output acquired from duck hunting. This business supports over 27,000 jobs (North American Bird Conservation Initiative, 2013, p. 6). Although the above examples are most influential on a monetary scale, there are aesthetic benefits of wetlands whether that be the croaking of frogs or the presence of tree swallows. Commercial development in Massachusetts comes with copious amounts of impervious surface creating runoff that ultimately impacts our public surface waters, and destroys habitat for wildlife. When developing commercial properties in Massachusetts, developers should be required to construct a wetland that effectively provides runoff control and habitat value.
The urbanization of America has introduced new impacts and obstacles for the natural systems of the Earth to deal with. With more people, buildings and cars, come more sidewalks, parking lots and roads. Impermeable road surfaces have increased the amount of pollutants in areas that are washed away by rain water into natural streams, rivers, bays, and even ground water (NACHI, 2006). This list of pollutants includes fertilizers, pesticides, household chemicals, and even oil and gas from cars. Not only do these pollutants enter waterways, but they flow at an accelerated rate due to the vast area of impermeable surfaces that previous to development were porous (NACHI, 2006). In recent years, developments such as shopping malls and corporate parks have implemented techniques of dealing with the collection of stormwater from parking lots.
One common use of water management in new developments are small man made lakes/ponds. These are known as detention ponds and their only function is to retain urban runoff in a basin to control excess flooding. These types of methods to control runoff are also called best management practices (BMP).
Another type of BMP for modern developments are constructed wetlands. Constructed wetlands normally have more vegetation than a detention basin and they are more efficient in filtering out sediment and pollutants from runoff (NACHI, 2006). Different types of man made wetlands exist to cater to different filtering needs and site applications. Each approach can be combined with other techniques to maximize the removal of sediment, pollutants, and also to control flow rates. It starts by collecting and controlling the path of the stormwater and directing it toward the constructed filtration system. This can be done using strips of vegetation between lanes in parking lots to direct the water from the asphalt to the wetland . The water first collects in what is called a forebay, which is the first stop in the system. This small detention area is normally about four feet deep but can exceed this depth as long as it is not excavated below the seasonally high groundwater line (DEP, 2002, p. 14). This acts as a pretreatment to a larger BMP such as dry detention basins, wet basins, and constructed stormwater wetlands. The forebay helps slow stormwater runoff and allows sediment to settle to the bottom before the water moves on to the next process (DEP, 2002, p. 15). Separating the forebay and the actual wetland is a wall of cut stone. These large cut stones are wrapped in a metal mesh in order for the wall to hold its shape over time. By creating this buffer between water bodies, these stones help keep the large sediment in the forebay rather than flowing towards natural water supplies. The water then moves on to a man-made wetland that is much larger than the sediment forebay. The wetland consists of a liner that insures total detention control as the water is naturally filtered by a series of high and low cut marsh. The water then moves on from wetland to our natural streams and rivers. Once the constructed wetland is in place it will require minimal maintenance throughout its lifetime. The sediment forebay needs cleaning once a year to prevent buildup of sediment. This ensures the entire system functions properly. The wetland containing the marsh needs to be monitored, but only requires a cleaning once every ten years (DEP, 2002, p. 37 ).
With more natural land being converted into urban developments this raises more concern about runoff control. Constructed wetlands are a great way to deal with flooding while also naturally filtering urban runoff before it enters our streams, rivers, lakes and bays. It is no longer a question whether or not we should implement urban runoff management control, but rather where it will be most affective. A study of oil and grease in urban runoff by Michael and Strenstrom (1984) took water samples from various types of land developments through seven separate storms. The study found that commercial property and parking lots combined held the highest concentrations of pollutants across all of their test sites. Parking lots held about 15.3mg/L of grease versus a residential area that only held about 4.1mg/L–this is also proportional to the amount of rainfall (p.128). A simulation of BMP indicated a possible 90% reduction in oil and grease discharge in commercial properties and parking lots that would lead to a 53% reduction of total discharge (p.185). What is even more amazing is that commercial property and parking lots only represented 9.6% of surface area analysis in the study (p.99).
Not only can constructed wetlands be an effective means of stormwater control but they can also provide suitable habitat for wildlife. In Massachusetts there are many species that will take to a large variety of palustrine (marshy) habitats. The onsite placement of constructed wetlands plays a large role in their ability to attract wildlife. Isolating a constructed wetland by surrounding it with concrete is going to limit the ability of terrestrial species to immigrate. The best placement would be up against pre existing habitats to allow processes of colonization to take place. Another characteristic a constructed wetland needs to attract wildlife is a diverse array of structure, or microhabitats. For example, it would be crucial to have areas with open water for attracting painted turtles and breeding frogs like the eastern american toad (DeGraaf & Yamasaki, 2001). By also constructing areas with dense emergent vegetation you can successfully attract breeding spring peepers, and by providing stable water levels water muskrat and ribbon snakes may readily take up residence (DeGraaf & Yamasaki, 2001). Snags (standing dead tree) in a constructed wetland function as nesting sites and hunting perches, along with areas of shallow open water these could attract foraging belted kingfishers, nesting tree swallows, and mallards (DeGraaf & Yamasaki, 2001). Although species of significant conservation concern may not take up residence, having such habitats readily available could be instrumental in aiding migratory bird survival by providing an area to rest and refuel, or aid a diverse range of dispersing juveniles. This concept of pairing constructed wetlands with commercial properties is not new and in some regions of Massachusetts is relatively common. However, studies quantifying the positive effects of these constructed wetlands adjacent to commercial properties does not seem to have occurred. The following examples illustrate how constructed wetlands have been implemented in other regions of the country with success; mainly focused around commercial agriculture.
Constructed wetlands provide improved nesting conditions in agricultural drainage evaporation basins, and have also functioned as crucial feeding habitats following the Deepwater Horizon oil spill in the Gulf of Mexico. Davis et. al (2008) performed a nine year study measuring how nesting density, hatch rate, predation rate, and concentrations of environmental toxins changed for american avocet and black-necked stilt after constructed wetlands were built. They found that prior to constructing a wetland to deal with the agricultural wastewater, nesting density was 1.9 nests/ha. Nesting density of these two species increased to 17.6 nests/ha post construction with an average hatching success rate for the two species of 78% and a predation rate of <1% (Davis et. al, 2008, p. 147). There are no studies looking at these rates in natural wetlands or even the hatching success and predation rates pre constructed wetlands, but for birds in general, high levels of nest failure is the norm. The authors also looked at the concentration of selenium in the eggs of these two species pre and post constructed wetland. They found an average of 11.2 mg/g of selenium in the eggs before, and this precipitously dropped to an average of 2.85 mg/g after construction (Davis, 2008, p. 146). Again, these figures say nothing about the performance of constructed wetlands in regards to natural wetlands. They do however prove that breeding conditions for certain wetland obligate species can still be significantly productive when provided with constructed wetlands.
In the gulf coast region, coastal wetlands have been declining at an estimated rate of 10,000 acres per year (North American Bird Conservation Initiative, 2013, p. 7). These coastal wetlands are instrumental in providing habitat for breeding, wintering, and migrating birds. From 13 million waterfowl, including 90% of the continental population of mottled duck, to nearly every species of wading bird including the federally threatened wood stork and roseate spoonbill (North American Bird Conservation Initiative, 2013, p. 7). After the Deepwater Horizon oil spill in the gulf of mexico the migratory bird habitat initiative was launched to recreate those wetland ecosystems inundated with oil. Through use of financial incentives this initiative bargained with rice growers and other agricultural producers to use existing infrastructure (levees, pumps, tractors, disks, mowers, and other equipment) to provide migrating and wintering birds with suitable inland habitats and high-energy foods. In 2010 the initiative spanned throughout 8 states, 440,000 acres, and is still growing! These constructed wetlands have proven to be a critical asset in times of most need, from the horrendous Deepwater Horizon oil spill to the successive droughts that ensued (North American Bird Conservation Initiative, 2013, p. 9).
It is beneficial to create wetlands especially because the United States alone has lost so much of this valuable ecosystem in the past. Traditional commercial stormwater management practices have proven detrimental to receiving waterways. This has been reevaluated in recent years from flood control to water quality (Brown, 2005). For example, the Washington State Department of Ecology (WSDE) has recently updated its Nationwide Pollutant Discharge Elimination System (NPDES) permitting process to take a significant step towards comprehensive stormwater management (Wolfe, 20012). Research conducted in the Puget Sound area has proven a connection between “land clearing activities and adverse impacts to stream hydrology and in stream habitat quality” (Wolfe, 2012). The induction of salmon to the endangered species list has led to increased stormwater management and land development regulations, such as updating the NPDES permit program in Washington (Wolfe, 2012). NPDES is mandated by congress under the Clean Water Act of 1972 which states:
“all municipal, industrial and commercial facilities that discharge wastewater or stormwater directly from a point source… into a water of the United States (such as a lake, river, or ocean) must obtain a National Pollutant Discharge Elimination System (NPDES) permit. All permits are written to ensure the receiving waters will achieve their Water Quality Standards” (EPA NPDES, 2009).
The program uses a permitting process to require the implementation of certain methods to hinder polluted runoff from entering local water systems (EPA NPDES, 2009). Amendment of these permits will make Washington the first state to require low impact development (LID). LID is an extensive technique for “land use planning intended to minimize or mitigate the impact development has on the natural hydrologic regime and associated water related ecosystems (Wolfe, 2012).
The WSDE has provided a “2012 Stormwater Manual” that provides a more explicit list of site specific BMP’s for permit approval, “these BMPs will prioritize infiltration, dispersion, and bioretention particularly for small sites” (Wolfe, 2012). Also the current “flow control standard”, incorporated with LID performance functionality, match eight percent of the two year pre-developed peak flow rate. “This targets much lower and more frequent storms and will apply to all sites greater than 2,000 square feet of “hard surfaces,” mostly large sites that create stormwater issues that threaten local water quality, and various species habitat (Wolfe, 2012).
We are proposing that constructed wetlands would be the BMP for commercial sites that create excessive stormwater runoff. This presents a more holistic approach to land use and stormwater planning in Massachusetts (Wolfe, 2012). We propose an update to the Massachusetts NPDES. The change will require permits for site specific implementation of wetlands before construction. The Environmental Protection Agency (EPA) states, “Since its introduction in 1972, the NPDES permit program is responsible for significant improvements to our Nation’s water quality” (2009). We believe they should heighten their standards in Massachusetts to require onsite constructed wetlands for commercial developments with large parking lots to deal with stormwater. Businesses will be responsible for incurring this cost and Town Conservation Commissions will be responsible for enforcing and overseeing these regulations.
A mechanism for motivating positive feelings toward the new permit process, is the 1987 amendment to the Clean Water Act (CWA); section 319 “Nonpoint Source Management Program” (2013). Section 319 addresses the necessity for thorough federal leadership to help focus state and local nonpoint source stormwater pollution. The section claims that states will receive grant money to “support[s] a wide variety of activities including technical assistance, financial assistance, education, training, technology transfer, demonstration projects and monitoring to assess the success of specific nonpoint source implementation projects” (Clean Water Act 2013). States can submit their proposed funding plans to the EPA. If a state’s funding plan is consistent with grant eligibility requirements and procedures, EPA then awards the funds to the state. If Clean Water Act 319 funds are available, and they correlate with the state’s funding plan, then they are rewarded with the appropriate grant (Clean Water Act 2013).
We do not exactly believe this program should be incentivized. It is our social and environmental responsibility to take care of the Earth’s water system, especially since it is our destructive habits that are causing these issues. However, creating a rewards program can be one way to receive positive feedback. For example, Portland City Council has established a “Clean River Rewards” for taxpayers who manage stormwater on their property. “Registration types includes commercial, multi-family residential (three units or greater), industrial, and institutional properties” (Environmental Services 2013). For commercial properties you must manage your stormwater runoff from the roof of the building and paved locations. Our proposed “Massachusetts Clean Water Rewards” would specify, “Property required by MANPDES to create wetlands could receive an allowance to mitigate cost of construction so long as they provide runoff control and habitat value.”
Those resistant to the proposition of legally requiring constructed wetlands with commercial developments are going to be the entities incurring the cost. Making this a legal requirement will create an additional cost that currently does not exist. Change is always a controversial topic, and one that takes away from corporate profit is going to be met by a strong force of opposition. However, with strong support from the public this resistant audience can be overcome. The fact these commercial developments, with their vast amounts of impervious surface, have a significant impact on water quality is scientifically proven (Michael & Strenstrom, 1984). This heavily polluted runoff eventually ends up in our surface waters. The health of our waterways is a public concern because of its affect on our drinking water. Healthy waterways are also an instrumental component of healthy ecosystems. Not only will our water quality benefit but also the wildlife. It is time we put the financial responsibility on those that create the problem. In terms of cost effectiveness constructed wetlands are 50-90% cheaper than traditional techniques for water treatment. Grant opportunities are also an option for lessening the cost of these constructed wetlands. Requiring constructed wetlands is the most economic way for these corporate entities to own up to their civic responsibility of mitigating their ecological impact.
Brown, Rebekah, (2005). Impediments to Integrated Urban Stormwater Management: The Need for Industutional Reform. Environmental Management. Retrieved from http://link.springer.com/article/10.1007%2Fs00267-004-0217-4
Clean Water Act Section 319. (2013). Water: Polluted Runoff. Retrieved from: http://water.epa.gov/polwaste/nps/cwact.cfm
Davis, D. E., Hanson, C. H., & Hansen, R. B. (2008). Constructed wetland habitat for american avocet and black-necked stilt foraging and nesting. The Journal of Wildlife Management, 72(1), 143-151. Retrieved from Jstor, search term: constructed wetland
DeGraaf, M., Yamasaki, M. (2001). New England Wildlife: Habitat, Natural History, and Distribution. Lebanon, NH: University Press of New England.
EPA NPDES. (2009). Office of Wastewater Management. Retrieved from http://cfpub.epa.gov/npdes/
Environmental Services. (2013). Stormwater Discount Program. Retrieved from http://www.portlandoregon.gov/bes/41976
International Association of Home Inspectors (n.d.). Constructed Wetlands: The economic benefits of runoff control. Retrieved from http://www.nachi.org/contructedwetlands.html
Massachusetts Department of Environmental Protection (DEP). (2002). Structural BMP Specifications for the Massachusetts Stormwater Handbook. Volume 2, Chapter 2, pp. 2-132 Retreieved from http://www.mass.gov/dep/water/laws/v2c2.pdf
Massachusetts Surface Water Quality Standards, Division Of Water Pollution Control. (2002)
North American Bird Conservation Initiative, U.S. Committee, 2013. The State of the Birds 2013 Report on Private Lands. U.S. Department of Interior: Washington, D.C. 48 pages. Retrieved from: http://www.stateofthebirds.org
Stenstrom, M., Silerman, G., & Bursztynsky, T. (1984). “Oil and Grease In Urban Stormwaters.” J. Environ. Eng., 110(1), 58-72.
Wolfe, M. (2012). Proposed Changes to Washington State Municipal Stormwater Permits May Have Far-Reaching Impacts. Environmental Science Association. Retrieved from http://www.esassoc.com/news/proposed-changes-washington- state-municipal-stormwater-permits-may-have-far-reaching-impacts