Pond Excavation
Anoka County residents frequently inquire how to improve their land for waterfowl or other wildlife. A common practice in Anoka County are pond excavations in seasonally saturated areas, or cattail-choked wetlands to provide an open water habitat.
The WCA regulates excavations in the permanently and semipermanently flooded areas of type 3, 4 or 5 wetlands and also regulates the placement of spoil and the depth of the excavation in all types of wetlands. Also, other jurisdictions including the US Corps of Engineers may have regulatory authority on wetland excavation projects.
Draining: There is potential for pond excavations to drain adjacent wetland areas. Typically, in Anoka County, if the hydrology is predominantly groundwater driven, a pond excavation can be designed that will not drain adjacent wetlands. However, some Anoka County wetlands are surface water driven, which increases the likelihood that a pond excavation could drain adjacent wetlands. This is an issue that is best addressed by your LGU during a specific project.
Filling: Filling of wetlands must be avoided during pond excavations. The spoil from the excavation must be placed in an upland area. A qualified wetland professional may be needed to ensure that the destination of the spoil is upland. Rarely, some soil deposition in wetlands during excavation is allowable if certified by the wetland specialist at the ACD.
Proper erosion control practices must be incorporated. You may contact the ACD for assistance with an erosion control plan.
Recommendations for Waterfowl Ponds
- Excavations should only be constructed in wetlands
that are degraded by invasive species such as reed canary grass (Phalaris
arundinacea).
- Ponds should only be constructed if other open-water wetlands are greater than 1/2 mile away.
- Proper open water depth is 1.5' to 3.0' deep. It can
not exceed 6.5' deep.
- Gradual flat slopes at the boundaries. A 10:1 slope
is preferred.
- An undulating bottom is very desirable to allow interspersion of vegetation and open water.
- Adding islands are not recommended unless they are
at least 300 feet from shore because predators can swim and destroy
nests. Also, they tend to concentrate Canada geese which can become
a nuisance. Nest
structures are a good alternative to islands.
- Creating irregular shorelines with points and bays.
In general, the more shoreline the better.
- "Wildlife
Habitat Improvement in Wetlands" is guidance for agencies to
determine when excavations in wetlands should be permitted.
| Water Depth | % of Pond at this depth | Likely Result |
| 0 - 1 foot | 5 to 15% | Cattails and emergent vegetation, usually dry by July |
| 1 - 3 feet | 40 to 70% | Mixed emergent vegetation and open water, dry in drought |
| 3 - 5 feet | 25 to 50% | Mostly open water, dry in severe drought |
Native grasses and forbs should be seeded in areas after final grading. Please contact Dennis Rodacker at the ACD for more information.
RELATED TOPICS: Ditch Maintenance and Peat Mining
