Many state, county and municipal departments of transportation (DOTs) are spending significant amounts of financial resources on stormwater management; especially for the Municipal Separate Stormwater Sewer System (MS4) Permit requirements for post-construction best management practices. Is this really an environmentally and financially sound approach to protect water quality?
Maybe I am missing something, but I have not seen any technical water quality studies performed by the Colorado Department of Public Health and Environment (CDPHE), the Environmental Protection Agency (EPA) or the United States Geologic Survey (USGS) to quantify and demonstrate the environmental cost/benefit associated with highway system post-construction BMPs here in Colorado and in other states.
Is local, watershed, and regional water quality actually being improved from having transportation projects design, construct, and maintain expensive post construction BMPs? Is this regulatory and stormwater management approach being used by many DOTs really sustainable? Do the millions of dollars spent by DOTs for construction and maintenance of post construction BMPS make environmental engineering sense? Why do the EPA and state regulators continue to force fit the MS4 model to transportation projects and corridors?
The MS4’s New Development and Redevelopment Program (NDRD) requirements (that are more applicable to urban municipalities than highway corridors) “shall include comprehensive planning procedures and controls to reduce the discharge of pollutants after construction is complete, from areas of new highway development and significant redevelopment and associated drainages. The program must ensure that permanent controls are in place that would prevent or minimize water quality impacts” (CDOT 2007 MS4 Permit). Constructing and maintaining post-construction BMPs for the sake of following an inflexible standard or guidance needs to be revaluated by DOTs and regulators.
In my opinion, it does makes sense to design, construct and maintain post construction BMPs that collect, treat and discharge stormwater collected from highway impervious areas that directly discharge into any surface water system; especially if traction sand is used for wintertime maintenance operations. This BMP implementation can be thought of as a mitigation requirement called out in the NEPA document to address a surface water impact. These BMPs can protect the surface water system from sediment loading, heavy metals and other pollutants; but do little to treat salt-based chemical deicing chemicals and poly aromatic hydrocarbons.
It does not seem logical that blindly placing structural BMPs beneath every drainage culvert along a highway corridor within a MS4 area will protect water quality and is sustainably sound.
A new way is needed here in Colorado and in other state DOTs that looks at stormwater management in terms of a watershed-ecosystem based approach.
In a watershed perspective, the surface area associated with highway right of way and impervious areas is very small in relationship to the entire watershed. In urban areas the amount of impervious surface area is dominated by parking lots, homes, driveways and municipal streets. The MS4 NDRD program requirements are really geared towards the municipal/urban setting. Transportation projects are being forced by some inflexible regulatory agencies to institute post construction BMPs in areas without adequate right of way (thus requiring costly land acquisition) and placing them in locations where there is no direct discharge into surface waters. There is some resistance by some regulatory agencies and DOTs to use regional stormwater ponds, and banking/trading those are more cost effective and protective than individual culvert discharge BMPs.
Stormwater from highway runoff needs to be managed in a new way that actually improves the watershed’s water quality and ecosystem. The implementation of post construction BMPs should be watershed-ecosystem based; meaning they should be located within the project area and/or within the watershed where they will actually improve water quality and the complex ecosystem. This watershed based concept is not new to some DOTs.
A watershed approach for transportation projects has been shown to work well in eastern portions of the United States. The strategy promotes the integration of both public and private stakeholder interests in working toward a common goal to support the sustainable use of natural resources within a watershed context. The objective of a watershed based approach is to implement a collaborative, watershed-based approach to storm water management that focuses on water quality results. Highways systems need to coexist with other land uses and have cost effective storm water management approaches providing watershed protection and improvements. It follows then that DOT stormwater programs need to integrate planning, maintain flexibility, and focus on outcomes.
The Principles used by the Mid-Atlantic Green Highways Partnership are straightforward and progressive:
- Delivering transportation programs including effective stormwater management in ways that address resource protection issues in the most effective ways in addressing watershed-wide needs
- Effective stormwater management should be done for the benefit of multiple stakeholders such as highway agencies and environmental protection agencies to achieve “better than before”
- Flexible approaches to implement and meet the desired goals of regulatory programs to protect natural resources
- Cost effective approaches to derive watershed benefits that are identified and promoted
- Promote integrated water and habitat resource protection (i.e. Storm Water and Watershed plans) into highway project development and project features
- Use collaboration and partnerships to deliver watershed improvements
Watershed organization coordination and consultation by DOTs for project stormwater management is generally not often used by many DOTs.
The Green Highways Watershed Approach to stormwater management recognizes that highways coexist with other land uses within watersheds, and a collaborative approach provides an opportunity for highway agencies to plan and deliver the most cost-effective protection and improvements to watersheds. To aid in watershed recovery, address watershed impairments, and to be prepared to address future potential water quality standard requirements, designers must begin thinking outside of the right-of-way. The overall Green Highways Watershed approach encompasses the following (GreenHighways):
- Stormwater management plans should be an integral part of the project development and NEPA studies
- Watersheds’ water quality and land management needs should be the focus of stormwater management plans, not just on-site regulatory compliance
- Project minimum responsibilities should be established on regulatory compliance and a plan should consist of a combination of onsite and watershed-wide management opportunities including banking and trading.
- Both in-kind and out of kind BMPs should be part of the plan to obtain the best environmental result in a cost effective manner
- Coordinate with other projects when possible to coordinate and implement mitigation and enhancement strategies
The Maryland State Highway Administration (MDSHA) has made tremendous progress in developing watershed-based stormwater management strategies. Raja Veeramachaneni, in his career with MDSHA, became a pioneer in this area pointed out that conventional approaches to stormwater management are focused on point discharges and designed only to meet regulatory requirements. However, these practices don’t necessarily address watershed needs or improve water quality. To aid in watershed recovery, address watershed impairments, and still fulfill Total Maximum Daily Load (TMDL) requirements, designers must begin thinking outside of the right-of-way (State of Maryland).
In summary, I believe it is impractical to continue down the same old road without the metrics to show that local and regional water quality has been maintained and/or improved by expensive post-construction BMPS; to purchase right of way and design, construct, monitor and maintain post-construction BMPs when using a point discharge approach is not sustainable and cost effective towards protecting water quality. Here are some final thoughts about highway post-construction BMPs:
- Coordinate with watershed organizations, local municipalities and other stakeholders to decide upon the local and watershed placement of BMPs to protect water quality
- Place BMPs along roadsides and at bridges locations where they will actually protect water quality, such as near surface water systems and sensitive wetland/riparian areas
- Instead of spending financial resources on right of way acquisitions and designing and constructing BMPs in constrained areas or in areas not near surface water systems, fund watershed-ecosystem based projects outside the project area to actually improve water quality and enhance ecosystems
- Eliminate costly and ineffective BMPs in their placement along highway corridors
- Coordinate with local watershed organizations or state agencies to identify potential watershed based projects that will address TMDL sources and ecosystem stressors
- Spending financial resources directly within the watershed for remediation or enhancement projects will have a direct positive impact on the environment and will significantly reduce DOT BMP life cycle costs and improve the aesthetic and recreational experience for the community; a real sustainable scenario
- The reduction in the purchasing additional right of way property to accommodate ineffective BMPs would be a significant cost savings to highway projects
- The watershed-ecosystem based stormwater approach would reduce the project life cycle costs and environmental risks to DOTs by reducing the number of BMPs to maintain, the operation and maintenance documentation to regulatory agencies, and the environmental oversight.