4.0. SR 12-15-1997~ty of
ITEM
MEMORANDUM
TO:
iver
MAYOR AND CITY COUNCIL
STEPHEN ROHLF, BUILDING
& ZONING ADMINISTRATOR
DATE:
DECEMBER 15, 1997
SUBJECT: LAKE ORONO STUDY AND
RECOMMENDATION
LAKESTUDY
HISTORY
Since May of 1995, the Lake Orono Sedimentation Task Force has been meeting to study
the lake. The task force is made up of volunteer members of the Lake Orono
Improvement Association with city staff support.
It was decided that additional expertise was needed to complete a formal lake study.
Wenck and Associates out of Maple Plain, Minnesota were selected in June of 1996 to
provide this expertise. Funding for the study came from Sherbume County, Sherburne
County Soil and Water Conservation District, the Elk River Lions Club, the Elk River
American Legion, the Lake Orono Improvement Association and the City of Elk River.
The lake study, which includes water quality and sedimentation issues, was completed in
October of 1997. The City Council has already received a draft of this study, but the final
version is included with this memo. The information contained in the study should
include the necessary data to obtain permits from the various governmental agencies that
will be involved if a lake improvement project is ordered by the Council.
WATER QUALITY
Contaminates - Sediment samples were analyzed for heavy metals, pesticides,
herbicides, PCBs, semi-volatile organic compounds and other substances (see page #3 of
the study). No significant levels of these materials were found in the sediment of the
lake. This is significant both as a public health issue and as far as disposing of material
that is dredged from the lake.
Phosphorus - Phosphorus levels in Lake Orono are fairly high when compared to other
lakes, but they are not high for a river. Lake Orono is basically a wide spot in the Elk
River. The phosphorus levels observed are not surprising for a hardwood forest river like
the Elk River. Leaves falling in the lake and river alone will significantly elevate the
levels of phosphorus. For more details on phosphorus see page #13 of the study.
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13065 Orono Parkway · P.O. Box 490 · Elk River, MN 55330 ° TDD & Phone: (612) 441-7420 · Fax: (612) 441-7425
Phosphorus is a nutrient which stimulates algae bloom or "dog days". Reducing the man
made sources of phosphorus will help reduce the frequency and intensity of algae blooms
in the lake, however, it will not eliminate these occurrences. Reducing the man made
sources of phosphorus should be pursued in both the Elk River and Lake Orono.
Fecal coliforms - In the summer of 1997, the city began monitoring the level of fecal
coliform at Orono Beach. The city's waste water treatment plant analyzes fecal coliform
levels in their discharge so they have the ability to run the tests at the beach. Diseases
may be associated with these waste born bacteria, so fecal coliform levels are a health
issue.
Significant levels of fecal coliform in July and August raised concerns. Staff did
additional tests to determine if the high levels of fecal coliforms were of humane or
animal origin. Fecal coliform of animal origin is not consider as much of a health threat
as those from humane origin. In general, the elevated levels of fecal coliform were
determined to be of animal origin (see page #15 of the study). It is theorized that a likely
source of the fecal matter is geese. Weekly monitoring for fecal coliform should be
conducted throughout the swimming season.
SEDIMENTATION
Suspended sediment - The study revealed that more suspended sediment is leaving the
lake then there is entering the lake. This was determined by monitoring the inlet and
outlet of the lake for suspended sediment. Staff feels suspended sediment is not a major
issue because the lake is not large enough to settle it out and passes it through. See page
# 10 of the study for details on suspended sediment.
Bedload - Bedload is the heavier material transported by the Elk River and deposited in
the lake. The study estimates that the average rate of bedload being deposited in the lake
is 3,000 cubic yards (CY) per year. This is not an unusually high rate. However, sources
of erosion upstream from the lake should be eliminated as much as feasible. See page
#11 of the study for the discussion on sediment load.
Conclusions and Recommendations - Other conclusions and recommendations of the
study are found on pages 16 and 17.
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LAKE IMPROVEMENT RECOMMENDATIONS
Background - Lake Orono was incrementally lowered between October 15~ and 17th to
aid staff in determining the locations and quantities of sediment deposits in the lake.
Aerial photos of the lake were taken during this period by Laurie Mezera-Kerr of the
Building and Zoning staff. In addition, Belaire Excavating reviewed the lake when it was
lowered to determine how materials could be removed and gave the city cost estimates
for doing this work. MAP #1 attached shows the locations of the sediment deposits.
Is a project needed - Modest improvements to water quality in Lake Orono can be made.
These efforts should be ongoing to avoid having water quality in the lake decrease.
However, the most pressing issue facing Lake Orono is Bedload. If nothing is done
regarding bedload the lake will eventually fill-in and revert back to being a river. A
project is needed sometime.
When should a project be done - There are two issues driving the timing of a project.
The first issue is how quickly is bedload affecting the use of the lake. In the last decade,
the western most lobe of the has become nearly non-navigable. It is estimated that the
lobe of the lake immediately north of Highway 10 will experience significant bedload
impacts in the next fifty years (more or possibly less). When this happens half the lake
will be affected by bedload.
The other important issue to consider regarding the timing of a lake improvement project
is development pressures around the lake. Staffhas made contact with four property
owners with significant amounts of land near the lake that are open to the idea of having
material removed from the lake being deposited on their sites. These properties will be
receiving assessments for urban services in the near future and their properties will
probably not remain vacant for long. These development pressures are likely to come to
bear in 1998. The cost of a lake improvement project approximately doubles, if the
material excavated has to trucked away from the immediate lake area. If a project is
going to happen, it should be in the near future.
Priorities - MAP #2 identifies the areas of the lake that the task force considered for
improvement. This map was based on the sediment deposits identified on MAP #1. If all
of these areas where enhanced, a lake improvement project would literally cost millions
of dollars. Therefore it is important to set priorities. The following outlines the
recommended priorities of the task force:
AREA A - Area A is located at the outlet of a storm water pipe from Orono
Parkway. Very little sedimentation from erosion or construction activity enters
the lake from this pipe, but sand from Orono Parkway does. Removing sediment
from this area can not be readily accomplished from Orono Parkway; the lake
would have to be lowered to allow equipment on the lake bed. This area is not a
recommended priority at this time.
fSshrdoc~b&zXstever\lakeocc.doc
AREA B - Area B is three small patches of material that were barely exposed
with the lake lowered four feet. This area does not pose a danger to navigation.
Area B is not a recommended priority.
AREA C - Because it is a hazard to navigating the lake, excavating Area C to a
minimum depth of 3 feet is a recommended priority. It is further
recommended that the erosion form Cemetery Point, adjacent to this area, is
corrected prior to the excavation of Area C.
AREA D - All of the channels in Area D still had water with the lake lowered by
two feet. This area is not receiving a high amount of sediment. The culvert under
Highway 10 is filtered through a grassy channel that should not be disturbed.
There are, however, parts of Area D where it is anticipated that property owners
will want to improve their access. These areas will not improve the lake for the
general public and, therefore, should not be publicly funded. However, the city
could include these areas in our permit to help these private property owners
through the bureaucracy. Area D is not recommended as a priority.
AREA E - Area E is a storm sewer outlet south of City Hall. A pad for a back-
hoe to operate from could be built adjacent to this area to accommodate removal
of materials from this site now and in the future. However, there is not a lot of
material that needs removal at this time. Area E is not a recommended priority.
AREAS F &G - These areas were only exposed when the lake was lowered by
four feet and access to these areas will be extremely difficult. Areas F & G are
not recommended as priorities.
Area H - Except for the area directly adjacent to the shore, most of Area H was
not exposed with the lake lowered by two feet. Further, this area of the lake is
adjacent to Highway #10 and is used very little by the public. Area H is not a
recommended priority.
AREA I - This area is perhaps the most difficult to remove material from because
it is muck. A mass improvement to this area will not add a lot of benefit for the
general public and will probably be quite costly. There are no disposal sites
adjacent to this area. Limited access to this area is achievable via a city storm
sewer easement.
It may be advisable to just provide better access to the homes in this location.
Access is limited in the very northeast corner of Area I (the portion that was
exposed when the lake was two feet low). There is approximately 650 feet of
shoreline that would need to be dredged to accommodate this better access.
A sedimentation basin should also be considered adjacent to the storm sewer
outlet in this area. If a sedimentation area is created, it should be in a location that
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is accessible in the future for cleaning and publicly funded. It is recommended
that improved access and a sedimentation basin in Area I are priorities.
AREA J - The only portions of Area J exposed when the lake was two feet low
were adjacent to the islands in the northeast comer. However, these areas do not
pose a safety hazard for boating. There were other portions of this area that were
exposed by approximately one foot when the lake was lowered by four feet.
Removal of material from Areas J is not a recommended priority.
AREA K - The area directly northeast of Boy Scout Island is a navigational
hazard. In addition, since this sandbar is adjacent to the main current through the
lake, this material has the potential to migrate farther down stream. It is
recommended that removal of material from Area K is a priority.
It may be possible to deposit material from Area K on Boy Scout Island to make it
more conducive to camping. The city owns the majority of this island. Ifa lake
improvement project is pursued by the city, disposal of material on this island will
be further explored.
AREA L - Area L is where bedload from the Elk River is currently being
deposited. This lobe of the lake is barely navigable now. Excavation of sediment
from this area will provide more usable lake area for the general public and
storage for future bedload. Removal of material from Area L is recommended
as the highest priority.
AREA M - This area appeared to have adequate water even when the lake was
lowered by four feet to allow access to the properties in this location. Further, this
access does not appear to be in jeopardy form adjacent sedimentation; it is off to
the side of the main flow of the river. Removal of material from Area M is not
a recommended priority at this time.
AREA N - Area N was being considered as a sedimentation basin. Since a
sedimentation basin of significant width can not be accomplished in this location
and it is unlikely adequate depth can be achieved in the sandy conditions, this area
has been ruled out as a sedimentation basin. Other than some incidental
removal of material to improve access up river, this area is not a
recommended priority.
AREA O - Access to properties on the west end of Area O is limited. However,
excavation in this area will not benefit the general public and should be privately
funded. Area O is not a recommended priority.
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Disposal sites - MAPS #3 & #4 show the locations of the proposed disposal sites for
material excavated from the lake. Plans for the disposal will need to be prepared before
the property owners will agree to having their sites used for this purpose. In addition, to
avoid costly trucking, it is recommended that the amount of material removed from the
lake not exceed the capacity of the proposed disposal sites. The help of the City Engineer
will be required for both of these purposes.
How to proceed - If, from the information provided thus far, the Council does not rule
out a lake improvement project in the near future, staff recommends the following
additional information is gathered to better define the exact scope and timing of a project:
Lake Orono Improvement Association
· Determine how much of the project cost the lake owners are willing to absorb
without appealing the assessment.
· Recruit community support for a project.
City Engineer
· Determine reasonable quantities of materials that can be deposited on the
disposal sites and prepare plans for review by these property owners.
· Research timing issues related to development and improvements on or
adjacent to the disposal sites.
· Prepare a preliminary assessment role for lake owners.
Wenck and Associates
Start permitting process with US Army Corps of Engineers, DNR, and
MPCA. After all the information is gathered, the Council may not decide to
do a project. However, if timing issues dictate the necessity of 1998 project,
the aforementioned permits will not be ready in time unless the process begins
this winter. The city's Floodplain Ordinance requires a conditional use
permit for filling in floodfringe areas, but city staff will be responsible for this
process.
Estimated costs - FIGURE #1 contains total cost estimates for a range of possible
projects and a brake down of the cost of improving the individual areas recommended as
priorities.
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511 32
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OPEN WATER O. 'IF.
EMERGENT VEGETATION
FLOATING LEAF VEGETAllON F.I'.
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LEGEND
BRIDGE
UNITED STATEs H!GHWAY
COUNTY ROAD
SECTION UNE
SECTION NUMBER
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32 I 33
NOTES
MAP #2
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UNITED STATES HIGHWAY
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OPEN WATER
EMERGENT VEGETATION
ri OA'I'INI":, I FAF'
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MAP #3
SCATTERED
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SOUNDED
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MAP #4
29 28
32 33
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8
10
FIGURE # 1
High
Excavate Area L to a minimum depth between
4 and 5 feet (120,000 CY)
Excavate Area K to a minimum depth of 4 feet (7,000CY)
Excavate Area C to a minimum depth of 4 feet (27,000 CY)
Excavate a channel & sedimentation basin in Area I (2,000CY)
Site preparation and disposal Site #1 (25,000 CY)
Site preparation and disposal Site #2 (43,560 CY)
Site preparation and disposal Site #3 (14,500 CY)
Site preparation and disposal Site #4 (5,000CY)
Site preparation and disposal Site #5 (22,000 CY)
Trucking to Site #1
River diversion
Trucking to gravel pits (43,940CY)
$372,000
$21,700
$122,900
$18,800
$32,700
$57,545
$19,315
$6,700
$29,065
$77,500
$50,000
$276,822
28% overhead
$1,085,047
$303,813
$1,388,860
This options addresses all of the priority areas to a high level and should
create enough bedload storage in Area L to last forty years. An additional
disposal site (Site #5) where material from Area C is trucked to is
necessitated with this option as well as trucking a portion of the material
from Areas L & K away from the immediate lake area; possibly the gravel
pits on Highway 169.
f:Xshrdoc\b&z\stever\lakoagda.doc
Minimum
Excavate the majority of Area L to a minimum depth of 3 feet
(60,000 cY)
*Site preparation and disposal on Site #2 (43,560 CY)
*Site preparation and disposal on Site #3 (14,500 CY)
River Diversion
$186,000
$57,545
$19,315
$50,000
Plus 28% overhead
$312,860
$87,6OO
$400,460
This project buys roughly 20 years before the bedload situation is equivalent
to today. If less work than what is described above is done, the costs of the
project probably out way the benefits.
*Disposal site preparation includes stripping top soil, spreading the
sediment, replacing top soil, and reseeding.
Mid Range
Excavate 90,000 CY from Area L making majority of this
area between 3 and 4 feet deep.
Excavate Area K to a minimum depth of 3 feet (3,500 CY)
Excavate Area C to a minimum depth of 3 feet (13,500 CY)
Excavate channel & sedimentation basin in Area I
(2,000 CY trucked to a site away from the lake)
Site preparation and disposal Site #1 (25,000 CY)
Site preparation and disposal Site #2 (43,560 CY)
Site preparation and disposal Site #3 (14,500 CY)
Site preparation and disposal Site #4 (13,500 CY)
Trucking to Site #1
River diversion
$279,000
$10,800
$22,950
$18,800
$32,000
$57,545
$19,315
$18,090
$77,500
$50,000
Plus 28% overhead
$586,000
$164,080
$750,080
This option should last for 30 years; a reasonable amount of time. In
addition, it provides a direct benefit to all portions of the lake and addresses
all of the areas recommended as priorities.
If Site #1 can be utilized without reloading material into on-road trucks, the
total cost for this option can be reduced by approximately $100,000 including
overhead. Staff feels overhead in general can be reduced.
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