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MN DNR: temporary improvements for boats: 30-acre dead zone.

posted Aug 17, 2015, 9:54 AM by Scott Slocum   [ updated Aug 18, 2015, 8:15 AM ]

To: Minnesota Department of Natural Resources

Division of Ecological and Water Resources
email: environmentalrev.dnr@state.mn.us

Re: Weaver Bottoms Aquatic Habitat Restoration Project EAW.

Thank you for the opportunity to comment on the Environment Assessment Worksheet (EAW) regarding the proposed dredging of an area in Weaver Bottoms. I am writing as a concerned citizen with a general scientific background; not as a specialist in wetland ecology or wetland management.

As I understand the project goals, they are to improve boating, fishing, and waterfowl hunting from boats in a small area adjacent to one of five boat-access points in the immediate vicinity (Anderson 2009, MN DNR 2015). The project would be funded as one part of the $5.25 million project "DNR Aquatic Habitat - Phase V" funded in 2014 by the MN Outdoor Heritage Fund (MN DNR 2014).

As I understand the methods, the project would use a backhoe to dredge an average of about four feet of sediment from a twenty-acre area of Pool #5 that has been filling with sediment from the Mississippi and Zumbro rivers. The dredged material would be placed on a nearby, ten-acre area of farmland. Attempts would be made to relocate visible, mobile fauna from each day's work zone in both the dredged area and the placement area, but all other flora and fauna in and around the transported material would be killed. The upland portion would be seeded back to pasture, and the waters would be left to recover naturally (MN DNR 2015). In a departure from the approach of other conservation organizations working in the area (The Nature Conservancy 2015, USFWS 2010) , there would not be any action taken to prevent the area from refilling with sediment. Given the certainty of continued sedimentation in the area, this project would need to be repeated periodically and perpetually into the future in order to maintain the desired water depth. There is no projection for the time interval between dredgings; it might be as infrequent as 80 years, or more frequently, depending on the rate of sedimentation, other considerations, and available funding.

I see the following problems with the EAW:

  • The EAW makes misleading references to historic Goose Lake (now also known as Prichard Lake), implying that the project would be a lake restoration; it would not. It would be a temporary restoration of an area of deep water along the edge of Pool #5--an area that would then gradually refill with sediment from the Mississippi and Zumbro rivers.

  • The only courses of action identified in the EAW seem to be 1) to implement the project or 2) to abandon the project in the unlikely event that it would involve the "disposal of contaminated materials" on the placement site. Another alternative that the EAW should realistically consider would be the option of leaving the area to continue to fill with sediment (and continue to be seasonally recharged with water from the Mississippi River), and presumably to develop into a shallow, flood-zone wetland.

  • The only conservation values identified in the EAW seem to be the project goals of improved boating, fishing, and hunting from boats. Other conservation values that the EAW should realistically consider include those of waterfowl habitat (distinct from the area's level of accessibility to hunters in boats) and non-game wildlife habitat (distinct from the area's levels of game production).

  • The EAW does not seem to consider the high costs of equipment, labor, and fossil fuels for the proposed project in light of its limited benefits of providing only a temporary fix in a small area for an unspecified number of years.

  • The EAW does not seem to include a projection for the rate of the re-sedimentation process, and thus the end date of the limited benefits of the proposed project and the date on which the process would need to be repeated (with the placement of dredged material on a new site each time).

  • The EAW does not seem to consider the potential impact of dredging the area perpetually into the future.

  • The EAW seems to attempt to downplay the fact that project would leave a 30-acre dead zone in its wake, each time it was repeated. Granted, the dredged area and the placement area would recover their flora and fauna within several years. But it would not be proper to overlook the grim aspects of creating such a dead zone. It would not be realistic to believe that the backhoe operators, truck drivers, and other personnel on-site would reliably and consistently clear the dredged and placement areas of submerged, subterranean, or otherwise concealed or inseparable wildlife before they pulled, piled, drained, trucked, and compacted the dredged sediments from one dead zone underwater to another underground.

Overall, I see a high cost/benefit ratio in this proposed dredging project, and I don't see a fair accounting for that in the EAW. The cost/benefit ratio of this project should be estimated in this EAW so that it can be compared by policy makers to those of alternative projects in soil-conservation, storm-water and waste-water runoff control, shoreline improvements, game and non-game wildlife conservation, game and non-game outdoor recreation, etc.

Personally and scientifically, I see the periodic creation of a 30-acre dead zone as a major drawback of the project, and I don't see a fair assessment of it in the EAW. The dredging and placement operations would be highly-destructive, and their results artificial; in contrast with the relatively harmonious, natural alternative of leaving the area to fill with sediment, and thus slowly transition to a different type of living habitat (similar to the wetlands that once surrounded historic Goose Lake).

In short, the EAW seems to be incomplete. It does not include a fair consideration of 1) alternative values and goals, 2) all environmental, financial, and energy costs, or 3) relative cost/benefit ratio.

If this EAW were complete and fair, I believe it would show that the preferred plan for areas like this along dam impoundments of the Mississippi River would be to allow sedimentation to continue, without dredging. Areas like this would continue to develop as wetlands on the food-plain, rich in wildlife, and high in environmental quality. These areas would continue to be valued by diverse interest groups, for diverse reasons. This EAW focuses only the interests of those who would boat, fish, or hunt from boats in areas like this. That's not acceptable.



Aerial view of the project area and surroundings

Google Maps, satellite image of Weaver Bottoms and surrounding area.

References