U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
This magazine is an archived publication and may contain dated technical, contact, and link information.
|Publication Number: Date: January/February 2002|
Issue No: Vol. 65 No. 4
Date: January/February 2002
Nevada. The word conjures up the image of a desert, perhaps with stark, towering snow-capped mountains in the background. Some may recognize that Nevada is a state rich in the history of the old west with boom towns turned to tumbleweed-choked ghost towns, silver mines, railroads, and Mark Twain. It may not occur to many people that Nevada is also home to a number of rivers, streams, lakes, and wetlands with lush vegetation and wildlife, but then, this is a very versatile and diverse state that can reveal many hidden treasures if you take the time to look.
|Washoe Lake with the foothills of the Sierra Nevada mountains in the background.|
Wetlands and riparian corridors abound in this desert climate, providing a beneficial resting and breeding ground to myriad migratory birds, reptiles, amphibians, mammals, and insects. As an effective ecosystem, a wetland acts as a natural contaminant filtration system and an area of groundwater recharge. In some wetlands, recreational activities such as hiking and bird watching can be enjoyed. The aesthetic qualities of wetlands should not be overlooked because they create a picturesque landscape for all passersby.
As water enters a wetland through streams, creeks, or washes, any pollutants are broken down by microorganisms living in the soils or on aquatic plants, and then the pollutants decompose into less harmful elements, such as carbon dioxide and water. Plants themselves can use nitrogen, phosphorus, and other compounds to remove excess nutrients from the wetland, thereby preventing an overgrowth of algae or other plants that could be detrimental to the health of the wetland.
Along with progress comes the inevitable loss of valuable wetlands; however, there are ways to help offset the impact. One way to help alleviate losses in wetland habitat due to development is a concept called "wetland mitigation banking." The process operates like a bank account in which a developer can restore, create, or improve an area before a development infringes on a wetland and from which a designated reserve amount of this restored or created area can be withdrawn. The new wetland can contain enough area to "mitigate" several impacted areas and perhaps, as in the case of the Washoe Lake wetlands mitigation site, still leave a balance that is available for future projects.
|Map showing location of the wetlands project.|
In cooperation with the Federal Highway Administration (FHWA), the Nevada Department of Transportation (NDOT) has created a wetland mitigation area in northern Nevada. This mitigation is required by the U.S. Army Corps of Engineers to offset unavoidable wetland losses in highway construction and maintenance projects in and around Reno and Carson City. The Corps of Engineers set a mitigation ratio of 3-to-1, meaning three acres are enhanced for every one acre lost. The area chosen, approximately 25 miles (40 kilometers) south of Reno at the south end of Washoe Lake, is sufficient for the required acreage and also provides available credits for future withdrawals.
In addition to FHWA, the Corps of Engineers, and NDOT, many other federal and state agencies have been involved in the development of the Washoe Lake Wetlands Mitigation Project, including the U.S. Environmental Protection Agency, U.S. Fish and Wildlife Service, Bureau of Reclamation, Nevada Division of Environmental Protection, Nevada Division of Wildlife, Nevada Division of State Parks, and Nevada Division of State Lands. Ted Bendure, environmental program manager for the Nevada Division of FHWA and previously an NDOT employee, was involved in the early stages of the mitigation project and continues to assist with the ongoing project development.
Through mitigation measures, critical wetland habitats can be preserved. However, the success of mitigation banking is dependent on numerous variables, and it can take several years for a wetland to become established. The fact that a mitigation bank can be created before the impact occurs allows time for the new or enhanced area to become effective, thereby eliminating any time without a wetland.
|Snow-capped Sierras with the pastoral mitigation area in the foreground|
When a mitigation bank is planned, it should be as close to the impacted area as possible, but if a separate mitigation area must be created away from the impacted area, then it should be within the same hydrographic region. A hydrographic region is defined as a geographic area drained by a major stream or an area composed of a drainage system made up of streams and lakes. The reason for staying close to the original site is that some species could be regional and might be lost if the mitigated wetland is outside that particular region. Potentially, if a species has particular requirements related to geography - such as a diet that includes specific plants that grow only at certain altitudes - the species would have limited areas to go to and could possibly die out, causing a loss in biodiversity for that region. If populations decrease due to habitat loss, the gene pool decreases, creating a loss in viable offspring.
The scenic Washoe Lake area that was chosen for the mitigation site is within the same Truckee River Hydrographic Basin as the impacted sites, and the pastoral mitigation site is entirely within the boundaries of a state park. A seasonal creek is the major tributary feeding the mitigation area. However, drought conditions occur frequently in this area, so a major expense was the development of a groundwater well and a surface water pump that will allow water levels to be controlled in spite of drought or other adverse conditions. This assured water supply supports wetland and riparian vegetation and other species necessary to sustain the delicate balance of nature in the area.
Washoe Lake is adjacent and north of the mitigation area. A levee separates the two. The project consists of 14 water impoundments, or ponds, created by five main levees and two cross-levees. These ponds have been constructed with varying depths to attract many species of waterfowl. Some species prefer a deeper water habitat that supports aquatic vegetation, and some prefer a shallow water habitat that sustains a more marshy emergent plant community. About 140 acres (57 hectares) are to be inundated every year to a maximum depth of 12 inches (30 centimeters) at each levee.
|Construction of a wetland.|
The mitigation site contains 110.5 acres (44.72 hectares) of permanent wetlands and 110.5 acres of open water for a total of 221 acres (89.4 hectares). The diverse habitat of the wetlands site permits a greater variety of species to take advantage of these additional wetlands and may help reduce the effects of overuse of other nearby recreational areas where water fowl populations are decreasing due to stresses and pollution caused by recreational activities. Since the Washoe Lake wetlands is a total, unfragmented area of 221 acres, it potentially offers more benefit to wildlife than the many small isolated riparian areas that were initially impacted.
The project was completed in two phases. Phase I, which contained 89 acres (36 hectares) of the total 221 acres, ended in 1988, and Phase II, which comprised the remaining 132 acres (53.4 hectares), was finished in June 1999.
After the levees were completed, the banks were vegetated with a mix of native riparian and upland plant species. Unfortunately, noxious weeds invaded the cleared areas. The primary weed of concern in the wetlands is Tall Whitetop (Lepidium latifolium), a species introduced from Europe and western Asia. It's an aggressive spreader and has the ability to crowd out beneficial native plants, degrade wildlife habitat, and increase erosion of the levee structures. This weed is capable of producing more than 6 billion viable seeds per acre and spreads by robust underground roots that can grow up to 10-feet- (3-meters) long and send up shoots to form new plants. Tall Whitetop can also reproduce from small segments of perennial roots broken from mowing, digging, pulling, or machine blading.
|A wetland pond inundated with Tall Whitetop.|
NDOT and State Parks are working together to control the infestation of the weed, and they are using the services of the state Department of Agriculture for chemical spraying and control of the plant. Special chemicals are required around water, and caution is exercised to avoid contamination. It is thought that Tall Whitetop can sometimes be drowned if kept saturated indefinitely; therefore, the ponds that had dried out and have an abundance of Tall Whitetop are being filled in the hope of eliminating the weed.
The site is also being improved to make it more of a multiple-use facility with recreational opportunities and to provide an aesthetically pleasing area to passersby on the roads on each side of the wetland.
An observation area is situated at the south end of the wetlands. The area has restroom facilities and a parking lot for cars and buses. The observation deck has informative signs and binoculars for viewing wildlife.
A new 14-foot (4.3-meter) observation deck, extending farther out into the constructed ponds, is under construction and will provide a better opportunity for school children, environmental enthusiasts, and the general public to get a "bird's eye view" of the wetlands. The funding for the deck was provided by a grant obtained by Nevada State Parks. NDOT Maintenance Crew 270 and the Environmental Services Division teamed together to remediate the wetlands further by dredging a channel from Washoe Lake to the surface water pump to increase the flow of additional water to the containment ponds. An additional 400-foot (122-meter) levee structure and a new pond were also constructed to offer better viewing and easier access to the new deck.
|Entrance to the observation area.|
Groups of students from the elementary school level to the university level tour the wetlands to gain an educational perspective in the operation of wetland ecosystems that are nestled within the arid lands of Nevada. The children, and adults too, can learn about the migratory birds and native mammals in and around a wetland environment. Local volunteers from the Audubon Society, the Nevada Division of Wildlife, State Parks, and NDOT accompany visitors on the interpretive tours. The system of levees provide accessible trails to walk on and the site is closed to visitors only during nesting season.
Rare animal species, like the bald eagle, have been seen hunting in the mitigation area. A sampling of other birds that occupy the area include osprey, red-tailed hawks, yellow-headed blackbirds, American coots, mallards, gadwalls, and northern pintails. California gulls, killdeer, Canada geese, willets, cinnamon teals, and other migratory birds have been seen at the wetlands.
If fortunate enough, visitors to the wetlands can catch a glimpse of mule deer, sometimes in herds as large as 20 or more, browsing peacefully beside the impoundment ponds.
Coyotes are often observed searching for their next meal of weasel, mouse, or perhaps an unfortunate young duck. This predator/prey relationship is another important learning tool for anyone touring the mitigation site, where the life cycle can be observed in action.
The property is owned by the Nevada Division of State Lands and is administered by the Nevada Division of State Parks. Maintenance funding for the project comes from NDOT, but State Parks carries out the maintenance activities. The Corps of Engineers requires five years of monitoring for Phase II by NDOT before they will accept the mitigation area as being successful. The monitoring for Phase I took place for three years from 1989 to 1991, and the Phase II monitoring will begin in 2002.
The Phase II monitoring criteria will include:
NDOT will submit a yearly monitoring report to the Corps of Engineers to report the wetland's status in relation to the criteria. One of the ways to track the progress is through aerial photographs taken each year in August, showing the entire mitigation area. The photos will be used to document the ecological progression of the wetland development.
|Wetlands with Washoe Lake in the background.|
When all the required criteria have been met, the Corps of Engineers will release NDOT from any further monitoring, but financial responsibility for maintenance will remain with NDOT in perpetuity.
Wetland mitigation banks require intensive study, planning, and execution, but they can provide an alternative to the destruction and permanent loss of vital wetlands and riparian habitats. Management of the site is a necessity to ensure the growth of native plants and the control of noxious and non-beneficial vegetation.
Even though Nevada is still a dry state with little rainfall, mitigation efforts can help to preserve, enhance, and restore the state's valuable wetlands that might otherwise be lost forever.
D. Gail Bellenger is a staff biologist for the Nevada Department of Transportation. She is responsible for performing environmental evaluations of project sites to ensure that no threatened or endangered species will be impacted. Duties also include obtaining necessary permits from the U.S. Army Corps of Engineers, consulting with agencies such as U.S. Fish and Wildlife on issues, writing environmental assessments (EAs), developing mitigation sites, conducting research on environmental issues, monitoring revegetated sites, delineating wetlands, and providing information to the public. Bellenger received two bachelor degrees from the University of Nevada, Reno, and she is working toward a master's degree.
The author acknowledges the assistance of Felicia Archer, Patty Brisbin, Chris Ennes, Daryl James, and Daniel Nollsch in developing this article.