Turning a Problem into an Asset
America's water resources have been in trouble for decades and it is our fault. We began cleaning up our water problems, beginning with the Clean Water Act of 1972, which initially focused upon "point source" pollution. More recent legislation expanded the effort to control "non-point source" pollution, most often associated with stormwater runoff. No doubt, these efforts have demonstrated successes, with numerous others to follow. These laws result in standard of minimum compliance and can be too restrictive upon the development potential of our resources, especially water. The restrictive nature of these laws makes it hard to see the real potential of stormwater management, which is economic potential.
As we try to establish minimum criteria for levels of sediment, hydrocarbons, phosphorus, mercury, etc., in our water -- at any given point in the water cycle, these levels immediately become the lowest level of quality we aim to achieve. We must also recognize that in our society, both change and quality are usually obtained with a hefty price tag attached. How can we begin to change our development perspective, if not our entire society, to encourage the maximization of our resources instead of minimization? The key is money, both present and future dollars. Current money flow appears to be primarily in one direction -- from the developer (or redeveloper) to the "community." Secondarily (and not to be dismissed as minor) is the flow from the community -- in the form of federal, state and local taxes.
How can we be assured developers and the community will benefit from all the expenditures? We can begin by analyzing the specific characteristics of each watershed, its limitations and potential, and then develop performance criteria, which preserves or improves current water quality standards at the lowest overall cost.
In response to current NPDES regulations, the developer might be required to filter surface runoff from the pavement areas, and then store a quantity of water equal to the difference between pre and post development runoff volumes.
New Development Approach
The U.S. Environmental Protection Agency (EPA) finalized the revised rule for the National Pollutant Discharge Elimination System (NPDES) Phase II permit in 1999 (EPA Federal Register, Vol. 64, No. 235, Dec. 1999) to include small municipal, separate storm sewer systems (those serving less than 100,000 persons) and construction sites that disturb one to five acres. The developments and communities who fall within the new parameter had to obtain coverage under the NPDES Phase II permit beginning in March 2003.
As a result on this new rule, EPA requires all new development sites over one acre are to meet stormwater quality and quantity criteria that results in some form of bio-filtration and/or storage on site. Lets say a developer selects a 20 acre parcel for a small retail center, and the site sits upon porous sand over a water table that lies 10 feet below the surface.
In response to current NPDES regulations, the developer might be required to filter surface runoff from the pavement areas, and then store a quantity of water equal to the difference between pre and post development runoff volumes. Because the runoff difference between hard surface (perhaps 90 percent of the developed site area) and sparsely vegetated sand is substantial, the resulting storage facility could be quite large and expensive. Depending upon the quality of the bio-filtration method used, the storage facility may even require waterproof lining with controlled release to a sewer, instead of direct infiltration release.
Traditional engineering solutions would involve pavement surface grading to drainage inlets, with conveyance by pipe, to a centralized outlet or storage facility -- a surface or subsurface pond arrangement. Filtration would likely occur in a new form of structural device prior to water entry into the storage unit. Storage and filtration elements become additional costs to the developer above the historical costs associated with pavement and stormwater collection and conveyance. Current community cost impact is relatively low.
Is this still maximizing the resource potential of this site within the context of watershed and community opportunity? The fact that this site could accommodate much higher runoff volumes and filtration from development uphill, that may not have the same porous soils, suggests this developer should be encouraged to maximize stormwater management opportunities of this site; with compensation from the community based upon the additional value delivered.
By stepping back and preparing a design which utilizes current and proven best management practices (BMP), the developer may actually be able to do more for less money. Roof runoff does not require extensive filtration, so this volume should not be directed to pavement surfaces to mix with polluted pavement runoff.
Porous pavements of reinforced grass or stabilized stone, such as Grasspave2, Gravelpave2 and PermaTurf, can percolate water at a much higher rate than rain can fall from the sky and act as bio-filters and storage devices at the same time. Placing porous pavements over native sand soils can eliminate need for inlets and conveyance devices and possibly even storage devices altogether.
Porous pavements of reinforced grass or stabilized stone can percolate water at a much higher rate than rain can fall from the sky and act as bio-filters and storage devices at the same time.
Porous pavement over clay soils can provide temporary storage and extend the time of concentration as water infiltrates and fills the void spaces in the pavement cross-section. Historical runoff volume differences between clay soils and hard surfaces are relatively low, so storage volumes in the porous pavement may satisfy at least a portion of total storage volume demand.
The developed cost of a site using porous paving instead of asphalt, may be slightly higher for the actual surfacing material -- base course, paving, fill, grass, labor. However, the reduction or elimination of drainage lines and detention basins has the potential to save the entire paved area15 to 30 percent in development costs. Porous pavement's life spans are two and 1/2 to three times that of asphalt, increasing savings. Long-term maintenance costs of asphalt can reach 40 percent more than its porous paving counterparts. Tax incentives could be used to maximize water development potential by the Developer.
Existing Development Approach
It is quite easy to point to all new development projects and demand conformance to new regulations, but what about existing communities that are suffering from aging and inadequate capacity of infrastructure? Indeed, many of our oldest communities suffer from old sewer facilities that carry both stormwater and wastewater (aka: combined sewers) and waste treatment plants that are dramatically undersized when storm flows are added.
Historically, the first response was to increase treatment plant capability, or to provide temporary large storage capacity offline, with deep tunnels. Both alternatives result in large community cost.
Using the more modern development approach of keeping storm and wastewater separate at the source, new technology offers similar advantages to existing development. By looking at each storm inlet source independently, breaking the direct connection to combined sewer outfall lines (CSO), and placing detention storage devices below grade between the inlet and CSO, temporary storage can be constructed and operated less expensively than with deep storage alternatives. Further, if soils below allow percolation, volumes would be reduced and treatment plants would not require expansion until justified by the wastewater stream. The entire stormwater flow would be gravity fed, eliminating the massive pumps needed to bring the deep storage water back to grade for treatment and discharge.
Shallow storage devices can be kept small to fit into available space offered by community owned streets, alleys and parks. Tax incentives or direct community payments, to private landowners accommodating storage on their property, could also benefit the community.
Many of our oldest communities suffer from old sewer facilities that carry both stormwater and wastewater (aka: combined sewers) and waste treatment plants that are dramatically undersized when storm flows are added.
Stormwater Reuse Values
Currently, we are going to great effort to clean and capture large volumes of stormwater prior to discharge into soils or continuation into streams and rivers. Stormwater is viewed as a problem that must be addressed and solved as quickly as possible. With this view we are missing potential values offered by this water -- irrigation use, non-potable domestic use and heat exchange.
Certainly in the arid western states, and perhaps other locations subject to periodic drought, water captured from roofs and pavements can be used directly for irrigation purposes. Along this same line, water captured from domestic non-wastewater sources can be added, blended and stored with stormwater sources for reuse. Other countries define this source stream as gray water, with some U.S. communities referring to their post wastewater treatment as non-potable sources. The biological activity present in landscaped areas offers additional filtration potential approaching tertiary quality.
Captured and stored stormwater can be used to pump back into residences for non-potable uses, such as watering plants and flushing toilets. In addition, water storage devices that are placed at least four to five feet below grade are subject to nearly constant geothermal heat. This heat source can be used to warm or cool buildings and pavements (snow melting) with the use of heat pumps designed for such purposes, by circulating water through the water held in storage. Air could also be used, but potential health hazards, such as molds, within the storage device limit direct air circulation use in buildings.
By reuse of captured stormwater at least once before disposal, pressure to expand water treatment plants is reduced; furthering the value returned to the community. A stormwater reuse policy can equate to using less -- a primary tenant of sustainable development. Such a policy may require federal coverage and empowerment in conjunction with current legislation.
Innovation and Economics
New technology and adaptive techniques develop in response to new laws and desires to protect our water resources. This new market continues to expand by removing or modifying older restrictive legislation against use of gray/recycled water -- including clarification of water ownership laws. Water protection increases more rapidly by creating new development currency exchange methods, such as development credits with economic value on a par with expenses. Opportunities to protect our water resources have the potential to save money and make economic sense for developers, the community and the nation.
Water protection opportunities exist beyond those we consider today. Let us make sure opportunities are not squandered due to lack of planning, oversight, restrictive legislation or unbalanced economic burden. We have the knowledge to make these changes. Let us make the tools to move boldly forward.
U.S. Environmental Protection Agency Web site on NPDES regulations and permitting program -- cfpub.epa.gov/npdes/
Water Infrastructure Network -- www.win-water.org
National Association of Flood and Stormwater Management Agencies -- www.nafsma.org
Stormwater Manager's Resource Center -- www.stormwatercenter.net
This article originally appeared in the April 2003 issue of Environmental Protection, Vol. 14, No. 3, p. 39.
This article originally appeared in the 04/01/2003 issue of Environmental Protection.