Oct 24, 2002

The Challenges of Stormwater Management

Stormwater Treatment

Stormwater management and its role in the larger challenge
of preservation of water quality around the world is an evolving issue. As
commercial development continues at record levels, both the quantity of runoff
and water quality are issues that need to be looked at carefully. The challenge
of how to better handle storing, treating and monitoring the stormwater runoff
from these developments without upgrading local drainage infrastructure or
sanitary sewer facilities is being shifted to the private sector. The
engineering community is being pushed to design new solutions that keep
groundwater and surface water ecology safe and that also protect development

New EPA Requirements

The increased pressure on engineers with regard to
stormwater is mainly attributable to the new Environmental Protection Agency's
National Pollutant Discharge Elimination System (NPDES) requirements. The EPA
finalized the revised rule for the NPDES Phase II permit in 1999 to include
small, municipal, separate storm sewer systems (those serving fewer than
100,000 persons) and construction sites that disturb one to five acres. The
developments and communities under this jurisdiction need to obtain coverage
under the NPDES permit by March 2003. The expectations are many. The EPA
expects "significant reductions in pollutant discharges and an improvement
in surface water quality" with this revised rule. It also believes the
rules will result in measurable financial, recreational and health benefits for
communities. They also expect benefits to wildlife, endangered and threatened
species and tourism as well as a reduction in the costs for siting reservoirs.

The Challenge for Municipalities

Stormwater is a challenge for municipalities that can affect
the community at the macro and micro level. From a macro standpoint, most local
municipalities that encompass a given watershed cannot handle the increased
runoff themselves, and rely on the water management district to develop a
solution. Essentially, the regulatory community has two choices in dealing with
the problem: build more municipal infrastructures to handle the runoff, or
create local regulation that requires those public or private developments to
detain or retain stormwater runoff onsite. The former option is obviously
costly and unlikely to be a viable solution to the problem. The latter, onsite
retention/detention, is the most realistic and environmentally-friendly

The Developers' Role

On a micro level, developers are faced with the challenge of
complying with the new, stricter regulations. They are looking for solutions
that are both effective and affordable within the scope of the development
project in question. If stormwater runoff must be stored onsite, then the
design of the new facility must make provisions for this volume of water. The
result is a challenge for sustainable development. The land developer must
weigh land utility against the cost and benefit of each potential solution.

Past Options, New Solutions

Ponds have been effectively used in the past to manage
stormwater. Escalating land values, public safety, maintenance, aesthetics and
the availability of new, cost-effective technology have brought the use of
ponds into question. The high construction costs associated with large diameter
pipe used for retention and detention have left some with the impression that
subsurface stormwater management is expensive. Large diameter pipe is equipment
and labor intensive because of its weight, the necessary fittings and the
significant machine time needed for installation. This pipe also offers little
design flexibility for odd shaped or constrained areas where subsurface storage
is needed.

The high cost of land has motivated engineers to look below
the surface for storage and treatment options. Conventional solutions such as
ponds are not a viable option when land values dictate utilization of every
possible developable area to make the economics work. Smart subsurface
technologies, coupled with water quality devices, are being viewed as the
answer. If water quality and quantity issues are handled subsurface, the
developer has more room for parking, landscaping or building and the municipality
is ensured environmentally effective treatment.

Depending on the site, subsurface treatment can provide the
best option for all parties. When the soil is used as a part of the treatment
process, just as it is for residential wastewater treatment, a large percentage
of contaminants can be removed naturally and effectively. When compared to
traditional approaches, subsurface stormwater management offers lower overall
installed cost, design flexibility and enhanced performance.

The Role of the Soil

Soil's inherent filtration capabilities are not new news. In
Delaware, sand filters have been used for years for the treatment of stormwater
runoff. Sand filters provide the necessary treatment values for many
municipalities around the Chesapeake Bay area, a highly sensitive watershed.
Biofiltration swales also are an accepted method of using a combination of
vegetation and soil to remove contaminants within stormwater runoff. Currently,
the California Transportation Dept. (CalTrans) is conducting roadway tests to
monitor the treatment of vegetated and non-vegetated slopes to infiltration

Infiltration can provide many treatment benefits. It also
provides groundwater recharge. Stormwater management plans are just now taking
into consideration the predevelopment infiltration rates on proposed
developments in order to replicate nature's own process of groundwater
recharge. As we continue to develop land and pave over permeable surface areas,
we not only change the surface hydrology by increasing peak runoff flows, but
we also dramatically change the subsurface hydrology. Replicating
predevelopment infiltration in post development has been deemed vital to
sustaining growth in some communities around the country. For those communities
that rely on groundwater for their potable water supplies, recharge to this
resource is imperative. Without recharge the resource can be depleted.

Regional Approaches to the Challenge

How stormwater management issues are addressed varies,
depending on the region of the country, the state and the municipality. Some
communities mandate zero net runoff or no more runoff from a site than in
preexisting conditions. However, due to a lack of funding, enforcement is
spotty. Some communities in California are developing task forces in which officers
travel to various construction sites inspecting for violations. In these cases,
the subject fines are generating the revenue for the continued enforcement.

One regional example where regulations have been developed
to solve local water problems is Southern California, where groundwater is a
crucial resource for the community. Currently, runoff is collected and
channeled to the ocean through huge concrete culverts to prevent flooding. This
concept of flood prevention is wasting water that could be recharging fresh
water aquifers under an area in dire need of potable water supplies. In the
past, Los Angeles has channeled its potable water all the way from the Colorado
River. This is an extremely costly program. Now, this stormwater is being used
to replenish Southern California's ever-depleting groundwater resources.
Throughout the area, the option of recharging groundwater resources instead of
channeling this fresh water to the ocean will sustain positive growth.

Massachusetts has a similar regulation regarding replication
of predevelopment infiltration rates in the post development form. This view
regards groundwater as a valuable resource. Nationwide, states that have
coastal areas or that encompass surface waters are following a "zero-net runoff"
model where all increases in stormwater runoff have to be stored onsite.

The states outside of EPA direct management (e.g.,
Massachusetts) have begun to develop training programs and workshops to learn
how to comply with the effects of the new Phase II requirements. Most of these
states have the resources in place to review compliance; however, development
costs may rise with more stringent regulations. Because these NPDES Phase II
permits are not required until 2003, smaller projects (those that do not fall
under Phase I) continue to be a main contributor to the stormwater problem.
These smaller projects are more prevalent than the larger five-acre
developments that have been required to provide, under NPDES Phase I, erosion
and runoff quantity control. After 2003, a one-acre development that previously
required no erosion control or stormwater management permit may now need one
under Phase II.

These new regulations do not mean that development costs on
these small sites will increase dramatically. Sometimes the controls needed are
minor and the use of new technology will make the controls more cost effective.
Municipal management is already in place for many of these developments as it
is for the communities under Phase I. The increase in developments affected by
regulation will drive regulatory agencies to create better tracking systems,
most likely electronic methods. Undoubtedly, there will be more capital costs
tied to regulatory monitoring. To assist with these new costs, the federal
government is making grants available for those who do not have the capital,
human resources or the departmental infrastructure to execute effective
programs. In these cases, the EPA offers to manage the programs for them. This
is already happening in nine regions.

The Stormwater Industry's Commitment

Some stormwater management companies are working to develop
economical and effective technologies that comply with regulations and
environmental codes, while allowing the developer to meet his space and
economic objectives. Economical, environmentally friendly solutions created by
the industry allow regulatory agencies and developers to harmoniously exist and
to improve our environment.

On the water quality side of the stormwater market, there
are many companies trying to achieve some national verification of their
technology. Many of these same companies are participating in the EPA's
Environmental Technologies Verification (ETV) program, using the program as a
vehicle toward attaining a national approval of their technologies. This
program is generating a standard protocol for testing of the treatment values
of the participating manufacturers in order to more accurately compare
technologies. Similarly, the water quantity side of the stormwater market also
is trying to follow nationally accepted standards, but the focus here is more
on the structural integrity of the technologies or the materials they use to
manufacture their products.

New Standards for Stormwater Products

Many new products are in development or have been recently
introduced to attempt to solve the problem of stormwater management. While some
of these new products do offer better treatment and safe groundwater recharge,
they are not all alike. In order to meet this new objective for stormwater
management, some manufacturers have taken a fresh look at the needs for the
technology and have raised the standard for product design, manufacturing and
testing to ensure performance above and beyond the AASHTO guidelines.

Technology, Testing and Performance

Subsurface systems require solid structural performance as
well as the engineered ability to address water quality issues. Structure
demands a rigorous analysis, nationally accepted design methodology, superior
manufacturing and materials to produce a technology that will satisfy the
industry performance needs. Currently there are no requirements or accepted
structural validation standards for water quantity technologies other than for
pipe and concrete systems. Nationally recognized standards for structural
performance, especially the AASHTO LRFD Design Methods for HS-20 Live Loads and
Earth Loads, are the best models to follow to validate technologies.

Environmental stress cracking is one problem that hampers
High Density Polyethylene (HDPE), the plastic used to manufacture products like
pipe. This is the premature initiation of cracking and embrittlement of a
plastic due to the simultaneous action of stress and strain and contact with
specific fluids. The source of the stress is often processed in during molding.
Therefore, applied stress is not a prerequisite for this condition. Some new
products are manufactured with polypropylene resins, a material inherently
resistant to environmental stress cracking. All systems should be thoroughly
tested. Engineers should take a look at how they evaluate and specify
subsurface stormwater systems to consider product design, structural integrity,
manufacturing and validation of performance.


Stormwater master planning is one way to address all of the needs
and potential threats to the watershed. However, implementation of these
practices can be difficult and may not be economically feasible for many
communities. Manufacturers who develop economical solutions that address
stormwater runoff issues can lead the industry and provide the regulatory
community with solutions that meet EPA standards. In order for a given
community to effectively enforce laws and regulations for the future they need
the technological support of the stormwater management industry today.

While technology will help solve the problem for new
development applications, the current status of our degrading water resources
is primarily from existing developments. Older, existing facilities must be
held accountable for managing their stormwater runoff. Strategies need to be
developed to retrofit existing developments, bringing them up to the new

In the future, water quality and water quantity will be
linked. Standardized testing protocols will be required for both. Conscientious
regulation will promote subsurface technology for groundwater recharge and
sustainable development.

About the author

Bryan A. Coppes is the vice president of research and development for Storm Tech, Inc. He is responsible for product development and R & D at Infiltrator Systems. Since 1993, he has been involved in the design process for Infiltrator's product lines and has assisted in establishing the StormTech subsidiary. Prior to joining Infiltrator Systems, Coppes worked in engineering and product development in the lift industry. He has a BS in mechanical engineering from the University of Connecticut and an MBA from Rensselaer Polytechnical Institute.