8.4.A. PRSR 04-1-2005Item # 8.4.A.
ver
MEMORANDUM
TO: Bill Maertz, Parks and Recreation Director
FROM: Rebecca Haug, Environmental Technician
DATE: April 6, 2005
SUBJECT: Sherburne County Ditch 31 pond in Woodland Trails Park
In January 2004, Sherburne County sent in an application to the City to work in County
Ditch 31 to clean out filled in silt, small brush, trees and grass. The application was sent
out by the City to the appropriate permitting agencies. The agencies gave permission to
the County to conduct the work. However, a Department of Natural Resources
(DNR) Public Water - PW 265 was drained in the process. This pond is located in
Woodland Trails Park.
Since this, the permitting agencies consisting of the DNR, Army Corps of Engineers
(ACOE), Board of Water & Soil Resources (BWSR), Soil & Water Conservation District
(SWCD) and Terry Mauer, Phil Hals, Steve Rohlf and I have been meeting with the
Sherburne County Ditch Inspector on a monthly basis to determine a method in which
to get the water back in the pond. The DNR is willing to allow for the pond to be
mitigated in a different location but after discussions with you, the agencies are under
the impression that the Park and Recreation Commission would like the pond back in
the same location.
The Soil and Water Conservation District (SWCD) and I took borings of the pond and
determined that it is a perched wetland. A perched wetland signifies that the moisture
is held in by a confining layer which in this case is a clay loam layer at about 5'. The
significance of this finding is that it makes it more difficult to keep water in the pond so
several different measures have been discussed.
One option has been to put in a control structure allowing for I week of impact. John
Norgren, Sherburne County Ditch Inspector has concerns with this method since it
could cause flooding to the property owners upstream. Excavating the pond was
discussed however, the ACOE rules are very strict on this and with the size and
location of the pond it would be extremely difficult to accomplish. It was also suggested
that a pipe could be installed throughout the area and possibly the wetland would hold
enough water before draining out. This would be costly. In addition, there may not be
enough drainage area to keep water in the pond.
At the March 17, 2005 meeting it was discussed that John would get on the County
Board agenda to discuss a ditch impoundment. The recommendation is to put in a
jersey barrier (ditch plug) to raise the ground water in the area approximately 2 feet or
as high as possible without causing flooding problems upstream and possibly pump water
into the wetland. The pumping would be done in June and then be observed to
determine how long it would take before the pond dried up. Phil Hals, Street
Superintendent spoke with Northern Dewatering and was informed that it would cost
$800/week to fill 4 acres per day. Some concerns with the pumping are maintenance
and getting the equipment back to the pond.
The SWCD will be installing monitoring wells to determine the effectiveness of putting
in a ditch plug. There will be a monitoring well and piezometer on the west side of the
wetland basin 200' south of the ditch and a monitoring well and piezometer on the east
side of the basin within 50' of the ditch. A depth gauge will also be installed in the ditch
to measure water depth. Elevations will need to be established for the wells. Water
levels would be recorded at each location on a weekly or every other week schedule.
The plan is to have these installed as soon as the frost goes out and before the jersey
barrier (ditch plug) is installed.
Unfortunately, the DNR Area Hydrologist who will make the final determination on
what is done with the pond was unable to make the meeting and has recently changed
jobs so at the next meeting which is scheduled for April 14, her supervisor will be in
attendance to let us know if this will be possible.
There is not an easy solution for this problem. Terry Mauer has been involved with the
discussions and doesn't see an easy solution for this problem. The jersey barrier may or
may not work but if the DNR gives its approval that will be the first step into putting
water back in the pond.
If you have any questions, please feel free to contact me. Thank you