IntroductionFor nearly two decades, wetlands have been restoredor constructed to meet a number of regulatory require-ments, including compensatory mitigation for wetlandlosses, treatment of wastewater, and reduction of non-point-source pollution. Wetland restoration attempts to reestablish ecological processes in damaged ordestroyed natural wetlands, while wetland constructionattempts to initiate wetland processes, typically on anon-wetland site, often for such purposes as improvingwater quality.

Technology DescriptionWetlands restoration and construction have been usedfrequently as mitigation to compensate for wetlandslost, typically due to construction projects. Wetlandscan be designed to provide specific functions lost fromthe landscape. These functions may include develop-ment of wetland plant communities that can providevaluable habitats for invertebrates, fish, and wildlife.They also include surface water storage, whichprovides for the absorption of stormwater flows, andretention, transformation, and removal of nutrients,sediments, and contaminants.

Restoration (Fig. 1) is used to replace wetlands oradjacent habitats eliminated during the remediation of contaminated sites. The restoration process isdesigned to replace the necessary soil structure andchemistry, soil microorganisms, and plant and animalcommunities. Both plants and soils can be salvagedfrom the remediation site, or ecologically similar sites,and used in restoration to decrease the recovery time.Following the final grading of clean soils, vegetation isplanted as seed or live plants. Species are selectedbased on the wetland type desired and are matched to the characteristics of the planting site, such as soilmoisture and light availability. Preparation of the soilincreases the successful growth of plants and oftenincludes loosening of compacted soils and addition oforganic material, such as decaying leaves. Streambankstabilization is often required for wetland restorationsalong stream channels to prevent erosion and quicklyestablish bank-lining vegetation. Stabilization methodsgenerally include use of plants (either as live plantsor seeds) in combination with natural or artificial fiberrolls or mats.

Constructed wetlands (see Fig. 2) are also now usedfrequently for the treatment of contaminated ornutrient-enriched wastewater. These wetlands typicallyreceive discharges from stormwater collectionsystems, sewage treatment systems, and otheroutfalls. Wetlands constructed for water treatmentmake use of natural wetland processes involving

P E C O N I C R I V E R R E M E D I A L A LT E R N AT I V E S

We t l a n d s R e s t o r a t i o n / C o n s t r u c t e d We t l a n d s

T E C H N O L O G Y F A C T S H E E T

Figure 1 Wetland restoration.

Figure 2 Wetland construction.

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plants, soil, and associated microorganisms. Thesewetlands are designed to reduce flow velocity, capturesuspended sediments, and adsorb contaminants. Asretention time of water within the wetlands isincreased, the effect of biological and nonbiologicalprocesses (both chemical and physical) that remove or transform organic and inorganic compounds, andincorporate materials such as metals into plant mate-rial or substrate, is also increased. Flow velocity maybe reduced by such design features as decreasing theslope of the wetland soil, increasing the density ofwetland vegetation, or reducing water depth bydispersal over a broader floodplain area in free watersurface systems (see Fig. 3).

Other applications of constructed wetlands includemitigation of surface runoff from agricultural fields,livestock operations, and golf courses. These wetlandsreduce surface flow velocities, retain sediments, andremove or transform nutrients or contaminants,improving water quality in downstream waters.

AdvantagesA diversity of wildlife habitats can be successfullydeveloped on restored or constructed wetland sites.Ecosystem function can be restored to degraded orimpacted wetland areas. Restoration can rapidlyestablish a stable biological community, including invertebrates and soil microorganisms. A good coverof fast-growing annual, as well as perennial, vegeta-tion can be established within the first year. Withinthree years, a wetland restoration effort can producea diverse community of desired plants and animals. In addition, constructed wetlands can be very effective in improving water quality in downstreamwaters. Constructed wetlands are effective inremoving or stabilizing sediments, metals, and organic contaminants.

DisadvantagesAlthough constructed wetlands may function as sediment retention systems, excessive amounts ofsediment can reduce function over time. In addition,contaminants immobilized in upstream sediments arenot eliminated by downstream constructed wetlands.These contaminants remain in place unless they areremoved using a separate remediation technology,such as phytoremediation or physical removal.

Relative CostThe degree of impact or alteration of the naturalwetland system influences the cost of successful

restoration. Soil replacement and grading canincrease the cost of restoration over that ofsimply preparing the existing soil and planting.Site-specific factors, such as slopes, watercurrents, or plant species required, can alsoinfluence the cost of wetland restoration. Ingeneral, restoring wetlands costs $3,500 to$80,000 per acre. This cost would increasewith planting of trees and shrubs. Initialconstruction costs of treatment wetlands arerelatively low compared with traditional watertreatment systems. Because the wetlandsrequire little maintenance, long-term costs are

also quite low. The cost of the constructed wetland isproportional to the number and sizes of treatmentcells required. In general, however, it costs $35,000to $150,000 per acre for constructed treatmentwetlands, or about 50% to 90% less than conven-tional treatment techniques.

Maturity of the TechnologyThe unique and complex characteristics of wetlandsthat are associated with specific wetland functions arewell understood, and these characteristics can beincorporated into restored and created wetlands in avariety of landscape settings. Many wetland restora-tion and creation projects have been undertaken inthe past two decades. Wetlands are often constructedor restored to provide specific functions, and thesuccess of both wetland construction and restorationprojects has greatly increased in the past 10 years.

The successful rehabilitation of degraded or impactedwetland systems includes revegetation, streambankstabilization, habitat creation for fish and wildlife, andcreation of new wetland areas. A variety of wetlandtypes can be restored, including stream-side wetlands

MeadowPondMarsh

InflowControl

StructureInfluent

InfluentDistribution

System

OrganicSubstrate

Flow

To Pond orReceivingSystem

Rip-RapWetlandPlants

EffluentCollectionSystem

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2" - 12"

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Figure 3 Free water surface wetland: marsh component.

composed of trees, shrubs, sedges, and cattails, as are found along the Peconic River.

Constructed wetlands have been used successfully forthe treatment of degraded water quality at many sitesfor various problems, including suspended sediments.Constructed wetlands have been shown to remove andtrap 86-100% of the sediments from water enteringthe wetland in summer.

Potential Technology Applicability –Peconic RiverThe potential impacts of the removal of contaminatedsediment from areas of the Peconic River include thedisturbance of wetlands within or adjacent to thestream channel. Wetlands are an integral component of the Peconic River system and provide numerousfunctions, such as waterfowl and fish habitat, and theyare an important component of a remediation program.Disturbed wetlands can be restored and exposedbanks and substrates stabilized in a cost-effectivemanner. For wetland restoration, clean soil will beadded to areas along the Peconic River from whichcontaminated sediments have been removed. The soilsurface will be contoured to match the pre-remediationelevation, and organic materials will be added. Plantsand seeds of desired species, such as those presentprior to sediment removal, will be planted. The desiredbiological communities will develop at these locationswithin several years and continue to increase in habitatvalue as the plants mature.

Constructed wetlands can be utilized to capture sedi-ments moving downstream from contamination sites.Application of this technology would aid in the reten-tion of contaminated sediments mobilized from unremediated areas of the Peconic River, therebypreventing migration of contaminants to downstreamareas. An open area of several acres would becleared, adjacent to the Peconic River, for theconstruction of one or more treatment cells. A gravityflow system may be used to convey Peconic Riverwater to the constructed wetlands, or a pumpingsystem may be installed. Contaminated sedimentsimmobilized in the Peconic River would not beremoved by this technology.

Following the completion of remedial activities, theconstructed wetlands may remain in place to continueproviding water quality improvements to the PeconicRiver.

Infrastructure RequirementsWetland restoration would not require additionalaccess roads or staging areas, other than thoseremaining from the remedial activities. Clean soil,plants, and other materials would be easily trans-ported directly to remediation sites. Construction of treatment wetlands requires access roads forconstruction equipment. However, decontaminationareas are not required.

Long-Term RemedyWetlands located within contamination zones will beleft undisturbed, unless contaminants are removedusing other technologies. Wetlands removed ordisturbed by application of other technologies willbe restored to pre-remediation conditions. A flood-plain location several acres in size, downstream ofthe contamination zones, can be utilized for theconstruction of treatment wetlands. One or morecells will be constructed adjacent to the riverchannel.

Process Residuals ManagementWetland restoration would be undertaken in areasremediated by other technologies, and thereforeprocess residuals are not expected. Contaminatedsediments trapped within the constructed treatmentwetland will remain in place. Organic and inorganiccontaminants will be primarily incorporated withinthe wetland substrate.

Site Closure RequirementsUnless other remedial technologies are used toextract or remove these metals from sedimentswithin the contaminant zones, the concentrations ofcopper, silver, and mercury will remain at presentlevels within the Peconic River sediments. Theconstructed wetlands will retain mobilized PeconicRiver sediments and adsorbed contaminants. Themetals will be stabilized primarily within the wetlandorganic and inorganic substrates.

Need for Site-Specific TestingRestoration of Peconic River wetlands would notrequire a pilot study prior to implementation. A pilotstudy, however, would provide valuable informationregarding the parameters for effective contaminanttreatment within constructed treatment wetlands. It will take about one year to conduct the pilotstudy. The unique aspects of the site, including

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hydrology, water chemistry, contaminants ofconcern, and suitable plant species, make a pilotstudy desirable to test and refine design criteriaprior to construction.

Need for Long-Term MonitoringFollowing wetland restoration or construction, a monitoring program will be maintained. Restoredwetlands in sediment removal areas will be moni-tored to identify changes in wetland quality or func-tions, such as erosion, insufficient growth ofwetland species, or introduction of invasive species.If other technologies are not utilized to removecontaminants from Peconic River sediments, amonitoring program will identify continued contami-nant effects. Wetlands constructed for treatment ofmobilized contaminants will be monitored periodi-cally for effectiveness of contaminant retention.

Synergy with Other TechnologiesShort of no action, wetland restoration will be imple-mented in coordination with other remediation tech-nologies, such as phytoremediation or sediment andcontaminant removal. Wetland restoration will restorePeconic River wetlands disturbed during sedimentremoval operations, or planting and harvesting, to pre-disturbance conditions. Restored wetland commu-nities, including habitat structure, plant and animalspecies, and hydrology, are expected to reflect undis-turbed regional wetland types. Wetlands constructedfor water quality improvement will be designed to retain sediments transported from upstream areas or for longer-term protection against inadvertentreleases.

ResourcesUSEPA, 1993, Constructed Wetlands for WastewaterTreatment and Wildlife Habitat

http://www.epa.gov/owow/wetlands/construc/

USEPA Guiding Principles for Constructed TreatmentWetlands: Providing Water Quality and Wildlife Habitat

http://www.epa.gov/owow/wetlands/constructed/guide.html

USEPA River Corridor and Wetland RestorationWebpage

http://www.epa.gov/owow/wetlands/construc/http://www.epa.gov/owow/wetlands/restore/

U.S. Army Corps of Engineers, EnvironmentalLaboratory, Wetlands Publications

http://www.wes.army.mil/el/wetlands/wlpubs.html

Natural Resource Conservation Center, WetlandScience Institute, Wetlands Restoration Webpage

http://www.pwrc.usgs.gov/wli/wetres.htm

ContactFor information regarding this fact sheet, pleasecontact Ken White (631/344-4423,kwwhite@bnl.gov).

This fact sheet was prepared by Argonne NationalLaboratory. Argonne National Laboratory is operatedby The University of Chicago for the U.S. Departmentof Energy under contract No. W-31-109-Eng-38.

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