Highly degraded State
owned lands could be used
for treatment of agricultural
S 1.6 3
WATER QUALITY MITIGATION
Mitigation is a term heard frequently in water management circles. Most often linked with
wetland impact permitting, mitigation is intended to offset an unavoidable impact to a
wetland. This impact is usually necessary to facilitate some desired type of upland
development. Wetland mitigation is also used to offset impacts to wetlands caused by the
development of a water supply wellfield.
Mitigation itself was discouraged around 20 years ago, as impact avoidance was the
common practice. Today the mitigation tool is widely used. Also the very nature of
mitigation has changed considerably over the last ten years. Until recently, mitigation
required "type-for-type" wetland replacement to offset the impacts to a wetland area.
Type-for-type means that if the impact is a cypress wetland, the restoration or creation
would focus on creating cypress wetlands only. Today, uplands are accepted in trade, as
well as different wetland habitat types from those affected. In the past, mitigation would
be required to occur on the impact site, or at least within the same hydrologic sub-basin.
Today, offsite mitigation is common. Even cash is an accepted unit of exchange to offset
S1 certain wetland impacts.
If mitigation is acceptable for wetland impacts, why shouldn't it be suitable for water
quality or quantity impacts? This concept is just now being accepted in some instances but
is still frowned upon by most water resource regulators. How would this concept work and
under what circumstances would it be a logical alternative?
An example that seems most appropriate involves road construction, especially road
expansions in developed areas. The conventional process to treat runoff water from roads
uses roadside swales or median swales to retain or detain a certain volume of runoff.
These swales require that additional right-of-way be acquired in order to accommodate the
area necessary for the swale and road system. Figure 8 provides a typical view of such a
conventional approach. In the event of an expansion of an existing road, especially
through an urban area, additional property must be condemned. In many cases private
homes and businesses are impacted; peoples' lives and livelihoods are disrupted resulting
in significant economic and social hardship. The expense associated with the acquisition
of these additional lands, and the public ill-will created by such actions, can be