Water: Best Management Practices
Subcategory: Innovative BMPs for Site Plans
Redevelopment is typically defined as development that occurs on previously developed land. The definitions of development and redevelopment vary in stormwater guidance documents and NPDES stormwater permits. However, both types of development require stormwater management.
In some states and localities, development and redevelopment are subject to the same requirements. For stormwater management, however, redevelopment of already-impervious surfaces can be a key strategy for reducing net increases in impervious surfaces and associated degradation to receiving waters. In watersheds that are experiencing growth, the reuse of impervious surface mitigates developmental impacts that would be experienced elsewhere. Where development takes place on undeveloped land, runoff is still generated on both the previously developed site and the new site.
Redevelopment can also deliver related benefits. For example, in established development districts, infrastructure upgrades can be used to repair deteriorating pipes contributing to water quality impairments.
Redevelopment can be accomplished on a site-by-site basis, but it can also be part of a larger effort to spur investment and development activity in a larger district. Common programs include business improvement districts (BIDs), Main Street programs for older downtowns, brownfields programs, vacant property campaigns and efforts to revive older, underperforming shopping malls. The transfer of development rights (or TDRs) can help spur redevelopment by directing development demand to existing activity centers.
Urban, suburban and even rural areas commonly contain vacant or underperforming properties. Individual jurisdictions within Economic Development offices or in the local Chamber of Commerce typically run programs to address redevelopment. For regional stormwater planning, though, efforts to coordinate redevelopment activity across a region or watershed can be viewed as both economic development and stormwater planning.Ultra-Urban Applicability
Redevelopment is highly useful in ultra urban areas, especially where the area is fully built out..Stormwater Retrofit
In areas with degraded waterways, redevelopment activity can complement efforts to improve the quality and reduce the quantity of stomwater runoff. The BMPs chosen for redevelopment, however, need to consider the unique circumstances of the redevelopment project. Micro-detention, urban forestry techniques and structured soils are often recommended for urban areas. Green building techniques and green roofs may also be good choices. As noted above, cities and counties will want to coordinate infrastrucuture repair and upgrades with redevelopment efforts so that water and wastewater capacity are not barriers to redevelopment.
Siting and Design Considerations
Redevelopment occurs on previously developed land. In districts with multiple redevelopment-ready properties, economic factors, such as location to amenities and proximity to transit, guide which properties are redeveloped first. However, these properties may not be the ones that will deliver the highest succession of stormwater benefits (e.g. for infrastructure repair or opportunities for detention).
Design Considerations and Variations
BMP design will vary considerably with land variations. Common land-constraints include irregularly-shaped properties, small lots, legacy contamination, and noncompliant building features/footprints. Water quality considerations can also influence BMP selection. In some cases, the main factor will be flow reduction, while in others cases the focus will be the filtration of nutrients or heavy metals.
Some of the strategies for redevelopment include:
- Green Roofs - Green roofs help reduce the urban "heat island" effect and reduce peak stormwater flows by absorbing stormwater onsite. The vegetated cover also helps protect and insulate the roof, extending its life and reducing heating and cooling costs.
- Micro-detention - Micro-detention techniques seek to absorb some or all stormwater runoff on the development site. Since the entire volume of stormwater generated on site is rarely entirely infiltrated, micro-detention is typically only one of a series of BMPs. Common landscaping features, such as small garden areas, tree grates, perimeter hedges, and even rain gardens (Bioretention (Rain Gardens)) can enhance stormwater handling and micro-detention. Since many urban buildings come with basements and underground garages, infiltration may occasionally not be an option. Pollutants that might be carried with infiltrating water should also be considered; hence, infiltrating techniques are not recommended for stormwater hotspots.
- Alternative pavers and porous pavement - Alternative pavers, porous asphalt, and permeable concrete reduce stormwater flows by allowing water to infiltrate their porous surfaces and soak into the ground beneath. Pervious pavers can reduce runoff volumes at a considerably lower cost than traditional stormdrain systems.
- Infrastructure upgrades - Storm sewer overflows and leaking older pipes (referred to as inflow and outflow) can be significant environmental problems in urban areas. Redevelopment offers an opportunity through enhanced tax revenue's resulting from increased economic activity to upgrade storm grates and pipes. However, capacity at wastewater treatment plants may be a barrier to redevelopment. In addition, the condition of receiving waters and TMDLs can be hurdles to any development activity in an urban area.
- In-pipe and small structural devices - A growing number of devices are coming on the market that provide a range of mitigation functions. These devices commonly work to separate large debris collected in runoff, intercept sediments, and improve water quality. They range in size, cost, and maintenance needs. They can be included in the suite of structural and nonstructural BMPs chosen for redevelopment projects and districts (for example, see Manufactured Products for Stormwater Inlets fact sheet).
As a stormwater strategy, redevelopment can require larger regional cooperation. To growing rural districts, a redevelopment strategy for established commercial centers might not be viewed as advantageous.
The BMPs required for redevelopment need to be compared to BMPs required for new development. Watersheds that choose redevelopment as a stormwater strategy should make sure the BMP cost and permit review requirements for redevelopment are comparable to those required for new development.
The effectiveness of redevelopment can be viewed at several scales. Where impervious surface replaces already existing impervious surface the site-level effectiveness may appear to be neutral. Where mitigation upgrades and BMPs are included, the site-level handling of stormwater may be more positive.
Where development demand is absorbed on already-developed parcels and steps are taken to protect other areas of the watershed, the watershed-level effectiveness can be more pronounced. In this sense, the effectiveness is preventative in nature. To quantify the runoff prevented, localities should compare the development intensity satisfied by redevelopment versus how that same development would look at another site in the watershed. Although building standards vary, the comparison should compare:
- building footprints
- number of parking spaces
- whether streets, turning lanes and access roads will be expanded with the development or redevelopment activity
- if the redevelopment project is mixed use, how the mix of uses is typically arranged when built new in other parts of the watershed
Because redevelopment is often more complex than new development, design and building costs can be higher.. Where infrastructure upgrades are needed, the costs can be considerable, particularly where treatment capacity or aging infrastructure is the limiting factor. However, in many cases, redevelopment projects can command a premium price and some or all of the costs can be recovered.
It is difficult to determine the watershed-level costs of various development patterns. For dispersed development, the costs are typically calculated site by site, where land-based infiltration, conveyance systems, or detention facilities are factored into project costs. This calculation, however, can overlook the costs of reduced water supply via infiltration and the "double costs" on a watershed when new development occurs even as existing buildings remain unfilled. These costs are likely to become more transparent with greater attention to watershed-based stormwater handling and mitigation.
EPA. No date. Smart Growth. [http://www.epa.gov/smartgrowth]. Accessed May 4, 2006.
National Vacant Properties Campaign. No date. National Vacant Properties Campaign: Creating Opportunity from Abandonment. [http://www.vacantproperties.org ]. Accessed May 4, 2006.
The National Trust for Historic Preservation. 2006. Main Street: Revitalizing Your Commercial District. [http://www.mainstreet.org ]. Accessed May 4, 2006.
The Smart Growth Network. 2006. Smart Growth Online. [http://www.smartgrowth.org ]. Accessed May 4, 2006.