Minnesota Water Resources Conference - Water Resources Center ...

Concurrent Sessions IV 10:00–11:30
Track D: Wetland Restoration and Mitigation Design Strategies
BOOK OF ABSTRACTS
Wednesday, Tuesday, October 24 28 23
Wetlands Restoration to Improve Water Quality
Lorin Hatch, HDR Engineering, Inc., lorin.hatch@hdrinc.com; Suresh Hettiarachchi, HDR Engineering, Inc.; and Renae Clark,
Minnehaha Creek Watershed District
The overall goal of this project is to decrease phosphorus (P) loading from Classen Creek to Stubbs Bay (Lake
Minnetonka). We are examining the feasibility of a Classen Creek wetland restoration project, located between
Classen Lake and Watertown Road, which is necessary to filter out sediment and P. As part of this project,
students from the University of Minnesota participated in a capstone project during the Fall 2007 semester to
update the water quantity/quality model in the Classen Creek watershed. The students also ran simulations
and concluded that construction of a berm to hold back water during spring runoff offered the best opportunity
to retain P in the wetland. 2008 work includes further refinement of the model and an examination of the
vegetation community in the wetland.
Wetland Mitigation Design: Flexibility from Concept to Construction
Lydia Nelson, HDR Engineering, Inc., Lydia.nelson@hdrinc.com; and Tony Luft, HDR Engineering, Inc.
Objective
The TH 212 Design-Build Project impacted 68 acres of wetland in the southwest Twin Cities Metro area. The
conceptual wetland mitigation approach initially focused on restoring previously drained/impacted wetlands,
rather than creating wetland from upland. The Design-Build contract required the on-site creation of 33 acres
of new wetland credits and 68 acres of public value credits, with the remaining mitigation made off-site. The
final mitigation plan was a combination of on-site new wetland and public value credits, off-site mitigation, and
wetland banking credits.
Methodology
The challenges for the project included a rapidly urbanizing setting, limited right-of-way availability, and
highway drainage requirements. Of the eleven sites identified in the conceptual plan, only five sites remained
as feasible options once the highway drainage design was completed. This presentation documents the design
process, key issues, key compromises, and successful completion of the mitigation requirements.
Conclusion
Large projects require a flexible and multi-faceted approach to meet regulatory requirements from multiple
agencies, to work within tight site constraints, and to fulfill the design requirements.
Minnesota Water Resources Conference, October 27–28, 2008 64