Site History

Between 1969 and 1995, a private gun club used an urban area known as Nahant Marsh for a trap and skeet range. Tons of lead shot were deposited in the marsh based on estimates by the gun club using shooting records. The lead shot fall zone contains mostly wetland habitats.

Nahant Marsh is located along the Mississippi River at the southwestern edge of the City of Davenport, Scott County, Iowa (Figure 1). Davenport is one of the municipalities that make up the Quad Cities. There are about 350,000 people in the Quad Cities.

The marsh is bordered by Interstate 280 to the south, agricultural fields to the west, an industrial park to the north, a railroad yard and municipal sewage treatment plant (STP) to the east. The marsh proper is owned by three parties including the gun club and two individuals that lease their land for corn and soybean production. The shot fall zone is believed to be entirely within the gun club property.

During the 1970's, one of the landowners adjacent to the gun club dredged recent sediments from a drainage ditch that the runs through the marsh and placed the spoil back into the water in violation of the Clean Water Act. The spoil was removed and placed in the woods next to the gun club shooting area as mitigation. The spoil may contain lead shot because it was originally located along the back extent of the shot fall zone. The density of shot in the spoil heap is expected to be very low because it was from 230 to 250 yards from the shooting platforms which is slightly greater than the traveling distance for small lead shot. Number 7 to 9 size lead shot travels up to 225 yards.

During the early 1980's, the U.S. Army Corps of Engineers - Rock Island District (USACOE) studied Nahant Marsh as part of an area flood protection project. A report was issued in 1982 by the USACOE that included information on local topography, hydrology and cultural resources for Nahant Marsh (USACOE 1982).

A citizen action group (River Action, Inc.) is in the process of developing a conservation plan for Nahant Marsh (see information in the newsletter in Appendix A). River Action, Inc. hopes to facilitate the purchase of the gun club property for use as an educational park. The gun club is interested in selling their property. The parties working with River Action, Inc. and interested in purchasing the Nahant Marsh property include the Iowa Natural Heritage Foundation, Augustana College (Rock Island, IL), Izaak Walton League, local and counties. The gun club now leases the property to a local motorcycle club.

In 1997, E & E conducted an integrated site assessment for Nahant Marsh under contract by the USEPA. E & E completed the following for the assessment: soil and sediment TCLP analysis, shot density estimates, chemical analysis of soils, wetland sediments and water. Nahant Marsh was listed in CERCLIS in 1997.

Site Visit

Natural resource personnel have monitored Nahant Marsh since 1994. In addition, local government officials, college researchers and field volunteers studied plant communities and wildlife use at the marsh for a local environmental education project. Lists of the plant, bird and small mammal species found at the site are in Appendix B. Scientific names for the plant and animal common names used in this report are in Appendix C.

Iowa Conservation Officer Ed Kocal, U.S. Fish and Wildlife Service (Service) Special Agent Walt Kocal, Service Contaminants Biologist Michael Coffey have periodically walked around the marsh with waterfowl hunting dogs to search for sick or dead birds. In addition, resource personnel have periodically canoed around the marsh to look for birds and collect field samples within the shot fall zone.

Search for Dead Birds

A total of five sick waterfowl and a grebe were recovered during the 1994 and 1997 site visits. Four of these birds were submitted to the National Wildlife Health Center(1) (NWHC) for examination by veterinary pathologists. One of the birds was submitted to the National Fish and Wildlife Forensics Laboratory(2) for examination by veterinary pathologists. The five waterfowl specimens were diagnosed with lead poisoning. The necropsy results are summarized in Table 1. The necropsy reports are in Appendix D.

At least fourteen scavenged waterfowl carcasses were seen along the marsh shoreline in 1994. These carcasses were believed to be sick birds taken by predators.

¹ The National Wildlife Health Center was a USFWS research facility that was eventually transferred to the U.S. Geological Survey when the National Biological Survey was formed. The facility employs board certified veterinary pathologists and provides wildlife necropsy and epidemiology services for the U.S. Department of Interior.

² The National Fish and Wildlife Forensics Laboratory is an USFWS forensics facility that employs board certified veterinary pathologists and provides wildlife necropsy services for the USFWS Division of Law Enforcement.

Table 1. Summary of necropsy findings for moribund birds recovered from Nahant Marsh in 1994 and 1997. The source of these data is from necropsy and related laboratory reports. The National Wildlife Health Center uses 6.7 micrograms of lead per gram of tissue wet weight as an elevated liver lead concentration and 27 micrograms of lead per gram of tissue wet weight as diagnostic of lead toxicosis.

Marsh Substrate Quality

There were different types of wetland substrates in the shot fall zone. Wetland substrate types included silty/sand areas, clay-muck bottom and organic substrates.

Wetland substrate samples near the gun club contained high densities of lead shot per grab sample. The area between 109 and 177 yards from the shooting platforms contained the highest density of lead shot. Samples containing up to 470 shot per square foot were collected by the USFWS at this distance. Samples containing up to 533 shot per square foot in the shot fall zone were collected by the USEPA contractor working at the site (E & E 1997)

Marsh Ecology

Nahant Marsh is in the floodplain of the Mississippi River, but is isolated from the river by a railroad grade levee. Floodwater from the Mississippi River can flow into Nahant Marsh through a ditch and culvert system that runs under Interstate highway 280 and through a series of wetlands that are between the Mississippi River and Nahant Marsh (Figure 2). The agricultural lands and industrial park also drain surface water into the marsh through a ditch system at the north end. Beaver dams at the marsh’s outlet help maintain deep water.

The Nahant Marsh system included 92 acres of wetland habitats, 43 acres of bottomland forest habitat and less than 10 acres dry grassy cover. The wetland habitats included a mosaic of cattail, bulrush and open water patches. The dominant bottomland forest tree species include silver maple, willow species and cottonwood. There are also patches of catalpa trees around the marsh. The grassy openings supported mostly the exotic nuisance species, reed canary grass.

Historically, the open areas around Nahant Marsh contained vast sedge meadows (Guldner 1960). Relict plant populations from these communities are present in some grassy openings. Plant species believed to be extirpated from Scott County (eg. Turtle head) were discovered in the grassy areas by amateur botanists.

Canada goose, mallard, woodduck and killdeer are some of the wetland bird species that nest at the marsh. Great-blue herons from a nearby rookery along the river commonly use the marsh as a feeding site. Large numbers (500 to 1000 per day) of waterfowl and other wetland bird species use the marsh during migration periods (pers. obs.). The other wetland bird species include the great egret, American coot, pied-billed grebe, common snipe, woodcock, rails and shorebirds. Bald eagles regularly forage at the marsh during the late winter and early spring. This area of the Mississippi River supports a large number of wintering bald eagles because of ice free water below the dam in Davenport.

Common wetland fauna such as frogs, snakes, turtles, small mammals and furbearers were observed at the marsh. Mammal species included deer mouse, vole, mink, muskrat, beaver and river otter. Frog species included northern leopard frog, western chorus frog and bullfrog. Snake species included water snake and garter snake. The turtle species include Blanding’s turtle, western painted turtle and common snapping turtle. The marsh fishery included the common carp, bowfin, green sunfish, bluegill and central mudminnow.

Nahant Marsh is part of a larger wetland complex that extends to the south side of Interstate Highway 280. The wetlands on the south side of the interstate includes another estimated 400 acres of marsh and forested wetlands.

The Nahant Marsh complex may provide suitable habitat for size dependent wetland species such as rails and yellow-headed blackbirds (Weller and Gredrickson 1974). Habitat suitability may not be optimum for these sensitive marsh species because of limited open water with submergent plant beds and lack of extensive grassy perimeter (Schroeder 1982). Most of the marsh is surrounded by woody habitats or developed lands.

The lead shot fall zone contains about 5 percent surface area of the Nahant Marsh complex. A wetland functional assessment was completed for the shot fall zone.

Wetland Functional Assessment Results

Wildlife Habitat The wetland portion of the lead shot fall zone is a characteristic hemimarsh habitat. Cattail and river bulrush are the dominant emergent plant species. The open water patches in the cattail usually contain small beds of coontail, pondweeds and duckweeds. There were no other obligate plant species observed in the wetland portion of shot fall zone.

The grassy portion of the shot fall area contains zones grading from the shoreline to wet meadow to dry weedy field habitats. The wetland plant species along the shoreline and in the wet meadow zone include arrowhead, sedges, rushes, horehound or bugleweed, wild iris, reed, reed canary grass and indigo bush.

The juxtaposition of the hemimarsh and this grassy area increases the suitability for wetland dependent species. Wetlands adjacent to grassy cover versus woods or cropfields are preferred by a variety of wetland species including ducks and rails.

Food chain production is likely high in the wetland portion of the shot fall zone. Aquatic submergent plants provide substrates for macroinvertebrates for birds and fishes. Aquatic submergent plant species and annual grasses produce seeds for a food source for migrating birds.

Fish Habitat The wetland portion of the shot fall zone does not have high fish habitat value. This area may support fish during wet years. The fish assemblage includes green sunfish, bluegill, bowfin and nuisance species such as common carp. During dry years the wetland portion has been a monotypic stand of cattail with little standing water.

Water Quality The wetland portion of the shot fall zone likely contributes to the overall function of improving water quality of agricultural run off and other upland surface run off. The water quality treatment function likely includes nutrient removal and sediment trapping. Denitrification and assimilation of nutrients can be high in a cattail habitat compared to other wetland types.

Natural Heritage Today, a small percent of Iowa’s natural wetlands remain in the state and especially in urban areas. We believe that some the sedge wetlands and especially the wet meadow habitats at Nahant Marsh are relict components of the presettlement landscape. For this reason, we place high value on the wet grassy portion of the shot fall zone. The hydrology and soils may be ideal for restoration of high quality meadow communities even though the current plant community is not unique or rare.

Cultural There is good access to Nahant Marsh at the shot fall zone. This part of the marsh was developed for the gunclub and includes driveways, picnic spots and observational towers. However, recreational activities such as fishing and bird watching at the shot fall zone are limited at this time because the land is private.

Disturbances Noise pollution is high at Nahant Marsh. Interstate automobile traffic and railroad yard activities contribute to the noise pollution problem.

Disturbances Associated with Response Alternatives Removal of up to a foot of substrate from within the deep emergent plant zone as a risk management action may or may not alter that plant community. Cattail communities are believed to quickly recolonize disturbed areas. Deep water may drown cattail or removal of hydric soils may expose underlying sand layers which may be unsuitable for many species of aquatic plants.

Deepening the deep emergent zone to create a pond habitat may or may not be beneficial. Creation of additional submergent vegetation beds along emergent plant stands improves habitat suitability for some unique wetland birds such as the yellow-head blackbird. The diversity of wetland animals may change if the depth of the water column is permanently increased to allow fish to overwinter and affect the wetland community structure.

Removal actions in the grassy portion of the shot fall zone could permanently change the existing grassy community. The wet meadow habitat may change to a deep water emergent plant community. The terrestrial old field habitat may change to a wet meadow habitat. Pioneer nuisance plant species such as the reed canary grass, may spread if not controlled because of the disturbance.

Many plant species in a meadow habitat have specific life history requirements often related to the amount and timing of water saturation. It is believed that restoration success rates of meadow communities are low because it may be difficult or costly to reproduce life history requirements.

The plant community in the wet meadow zone contains relatively common species and few native wetland forbs. The grass community of the meadow includes reed canary grass or small sedges. This part of the site also contains the clay target debris zone.

In summary, the wet grassy portion of the shot fall zone may be important and contribute significantly to the overall value of the Nahant Marsh ecosystem. The importance of the wet grassy opening in the shot fall zone is primarily based on potential wildlife habitat and natural heritage functions described above and not the quality of the existing plant community.

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