2017-12-04 CC Agenda Packetib:crtV1 IE
�Amun Wns.ft OWe. Mayor and Council Communication
November 30, 2017
SUBJECT: KARSTON COVE 4TH ADDITION CONCEPT PLAN
RECOMMENDATION: It is respectfully requested that the Mayor and Council consider the
attached Karston Cove concept plan submitted by Centra Homes and give direction to the
applicant and staff on the acceptability of the land use and subdivision design.
BACKGROUND:
In 2004, the City of Albertville approved Karston Cove CUP/PUD and plat that included 14
townhome lots north of 64th Street NE and 29 lots south of 64th Street NE. This development
was covered within the Karston Cove final plat and a planned unit development agreement that
outlined development requirements for this townhome subdivision. The 14 townhomes north of
64th Street NE have been developed and sold to individual homeowners. The 29 lots south of
64th Street NE, while final platted, remain undeveloped.
In 2009, the City and developer amended the development agreement giving the developer until
October 31, 2010 to complete all public improvements and all private on -site improvements to
develop the property. The developer went bankrupt in 2010 and never installed the required
improvements. The City drew on the developer's letter of credit and is holding the money for
the improvements. In 2011, Centra Homes purchased the 29 undeveloped lots and the rights to
the letter of credit money from the bankrupt developer.
According to the City Attorney, the City had six years from the October 31, 2010 date to bring
suit against the developer's successor (Centra Homes) to have the improvements for the final plat
installed (see Exhibit B). The deadline was October 31, 2016.
The developer was not interested in building attached townhomes on the site. They have stated
that this housing type has become less popular within the current housing market. They also
cited that the 2003 models that were approved would not sell favorably in today's market.
As a means of addressing the issue of the expiring development agreement and the development
objectives of Centra Homes, they filed an application with the City to amend the Karston Cove
PUD agreement and they requested City action to vacate all the townhome lots in Bock 2 of
Karston Cove 3rd Addition and rep at this area into an outlot. By City ordinance, no building
permit shall be issued for an outot. Any future development will require this outot to be
subdivided into lots and blocks before building permits could be issued. Any future subdivision
will require City Planning Commission review and Council approval.
This application was approved in October 2016 by resolution with the following conditions:
1. The City retains the option to require the future development on Outlot A Karston Cove
4th Addition to join with the existing Karston Cove Homeowners Association (HOA) on
the north side of 64th Street NE through a revised PUD development agreement to be
Meeting Date: December 4, 2017
ends Page 34
Mayor and Council Communication —December 4, 2017
(Karston Cove 4th Addition Concept Plan) Page 2 of 5
recorded against the Outot A property with the future final plat. Notwithstanding this
reservation of rights, the City acknowledges that it may not impose any obligation on the
developer to add the future lots to the existing Karston Cove HOA unless the declaration
establishing the HOA has been modified, on or before the time of final plat approval, to
allow for the addition of the Outot A land to the Homeowners Association.
2. The City finds that the drainage and utility easements dedicated on the Karston Cove 3ra
Addition plat (but excluding those easements dedicated on the first plat of Karston Cove)
are no longer needed for public purposes and that it is in the interest of the public to
vacate said drainage and utility easements.
3. The City vacates the drainage and utility easements shown on the Karston Cove 3rd
Addition plat, provided the 41h Addition final plat is revised to preserve all drainage and
utility easements originally dedicated on the first plat of Karston Cove. Said easements
shall be subject to the review and approval of the City Engineer prior to recording the
final plat. The vacation of said easements shall be effective upon the recording of the
Karston Cove 4th Addition pat.
4. The City approves the preliminary and final plat of Karston Cove 4th Addition, subject to
the conditions set forth in the City Planner's report dated September 8, 2016, including
execution of a development agreement as set forth below.
5. The developer shall be required to install sidewalks per approved plans, boulevard
grading, and restoration to a turf condition by June 30, 2017 as a condition of final pat
approval, unless the developer submits a completed preliminary plat application for the
site by June 30, 2017, in which case the June 30, 2017 installation date shall be
automatically extended to June 30, 2018.
6. The applicant enters into a development agreement with the City that includes the
aforementioned conditions of approval, addresses the issues identified in the RCA for this
matter, and meets the approval of the City Attorney. The development agreement shall
be recorded against the property with the final plat.
7. Upon execution of the development agreement and recording of the plat, the City shall
release the monies it holds in escrow from the proceeds of the letter of credit for Karston
Cove 3rd Addition, except for an amount sufficient to cover 125% of the cost of the
installation of sidewalks, boulevard grading and restoration, and the anticipated expenses
of the City Attorney, Planner and Engineer related to Karston Cove 3rd Addition and
Karston Cove 4th Addition. The City Engineer shall determine the amount of escrow to
be held for the installation of such items and the City Finance Director shall determine
the remaining amount of escrow to be held to cover anticipated City expenses.
REZONING: Centra Homes has now submitted a concept plan for small lot single family
homes for consideration of the City council. The site is zoned R-5, Residential Medium Density
Multiple Family District. This district does not permit single family homes as an allowed use.
As such, a rezoning to PUD District will be required to allow this use and subdivision design.
P:1City Council\Council Packet Information1201711204171Karston Cove Replat Concept Council Coininunication.docx
Meeting Date: December 4, 2017
Agenda Page 35
Mayor and Council Communication —December 4, 2017
(Karston Cove 4th Addition Concept Plan) Page 3 of 5
The PUD District is necessary because all of Albertville's standard single family districts have
lot area, width and setbacks larger than what is being proposed with the Centra Homes concept
The PUD District would be needed to allow the following reasons:
1. To allow single family homes.
2. Lot Width: The concept plan shows lots have an average lot width of 65 feet. Albertville
standard single family districts do not allow lots this narrow. PUD flexibility is needed.
3. Setbacks: The concept plan shows approximately 15 feet between building pads. This
would also be a PUD flexibility.
4. Setback between Driveways: The City requires 40 feet between residential driveways.
The lots with the wetland in the front yard may not have the needed driveway separation
from the driveways on adjoining lots. This would be a PUD flexibility.
SUBDIVISION: SIGN: In addition to the rezoning, the applicant must also process a preliminary and
final plat subdividing the property.
KEY ISSUES:
• The single family subdivision without an association will not help the existing
association. The issue remains that the existing HOA is too small to be financially
successful. The applicant has been in contact with the existing HOA and has come to the
conclusion that the establishment of a Large Master HOA with two sub -associations is
impractical with regard to administration, board membership, shared services between
the sub -associations, and shared costs. They are requesting to be released from this
requirement. The existing HOA has been requested to attend the Council meeting to
share their thoughts on the matter.
• The single family subdivision proposes lots that range from 60 to 80 feet wide at the
building line. The lot areas without wetlands range from 10,800 to 12,600 square
feet. We have no zoning districts with single family lot standards that are this small. The
applicant must pursue a PUD zoning map amendment to allow this type of subdivision.
The physical configuration of the site and the existing wetlands and existing high water
levels complicate the placement of dwelling units and may not allow the provision of the
private street proposed with the previously approved townhome designs. The applicant
is proposing a lower density subdivision option.
• Two of the lots show a front yard wetland. This requires an unusual driveway
arrangement and will require flexibility from the required spacing between driveway
curb cuts.
All the homes will be set back from 64th Street NE right-of-way 30 feet or more.
P:1City Council\Council Packet Information1201711204171Karston Cove Replat Concept Council Coininunication.docx
Meeting Date: December 4, 2017
Agenda Page 36
Mayor and Council Communication —December 4, 2017
(Karston Cove 4th Addition Concept Plan) Page 4 of 5
• The scale of the plan is small and difficult to measure, but the side yards appear to be 10
feet from the east and west property lines of the plat and approximately 15 feet between
homes. The side yard setbacks will require PUD flexibility.
• The plat will need to demonstrate a 30 foot building setback and wetland buffer from the
edge of the delineated wetland boundary. The western two lots may raise some questions
depending on where the edge of the wetland is located. With new wetland criteria, we
will likely need a new wetland delineation.
• These are narrow lots for single family homes. Centra Homes must submit some
housing models that would be proposed for this plat to allow staff and the Council to
determine if they meet minimum standards and are comparable to the townhome
architecture in this area.
• We will require a landscape plan that screens the park parking lot, establishes the
wetland buffers, front yard trees, and restoration of ground cover if this plat proceeds
ahead.
The plat must show that each building pad will allow the following building elevations:
o Top of foundation and garage must be a minimum of 1.5 feet above the crown of
the abutting street.
o The lowest floor elevation for lots abutting a wetland or drainage way must be a
minimum of one foot above the normal water level (NWL).
o The low building opening elevation must be two feet above the 100 year flood
level (HWL) and two feet above the emergency overflow elevation (EOF)
• Staff has concerns regarding tearing up the street for nine separate utility services to each
of the new homes. The applicant will need to submit grading and drainage plans and
utility plans if this project proceeds.
• The unit count is reduced from 29 townhome units in the original PUD to nine single
family units.
POLICYIPRACTICES CONSIDERATIONS:
At this point, the Council is only being requested to comment on the concept plan. Review of a
concept plan does not convey any development rights; rather it provides direction to the
applicant and staff as to how to proceed with subsequent development applications. In reviewing
the concept plan, the Council is aware of the subsequent steps and should provide their opinions
based on the past approvals, the key issues, and whether the proposed use/subdivision can be
compatible with the surrounding land uses in the neighborhood.
FINANCIAL CONSIDERATIONS:
The concept plan presents no financial obligations to the City. The financial obligations outlined
in the original approval will remain in place until all conditions of the previous approval are met
or approval of a new subdivision for the parcel.
P:1City Council\Council Packet Information1201711204171Karston Cove Replat Concept Council Coininunication.docx
Meeting Date: December 4, 2017
Agenda Page 37
Mayor and Council Communication —December 4, 2017
(Karston Cove 4th Addition Concept Plan)
Page 5 of 5
LEGAL CONSIDERATIONS:
With the concept plan, the applicant is pursuing an alternative development plan for the property
in question consistent with the conditions of the October 2016 Council resolution vacating the
previous pat.
Department/Responsible Person:
Submitted Through:
Attachments: Exhibit A
Exhibit B
Exhibit C
Exhibit D
Exhibit E
Alan Brixius, City Planner
Adam Nafstad, City Administrator-PWD
Site Location
Original PUDI Pat
October 2016 Pat
October 2016 Council Resolution
2017 Centra Homes Concept Plan
P:1City Council\Council Packet Information1201711204171Karston Cove Replat Concept Council Coininunication.docx
Meeting Date: December 4, 2017
ends Page 38
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CITY of ALBERTVILLE
COUNTY of WRIGHT
STATE of MINNE SOTA
RESOLUTION No. 2 0 15-
RE SOLI TION APPROVING A PRELIMINARY AND FINAL PLAT FOR KARSTON
COVE 4TH ADDITION, AMENDMENTS To THE KARSTON COVE Ci PIPi D
DEVELOPMENT AGREEMENT, AND THE VACATION of SELECT EASEMENTS
WITHIN KARSTON COVE 4TH ADDITION
WITHIN THE CITY of ALBERTVILLE
WHEREAS, Centra North LLC has submitted application for an amended CUPIPUD, a
preliminary plat, final plat, and vacation of easements with a subdivision entitled Karston Cove
4th Addition and the proposed plat vacates 29 townhome lots and one common lot in Block 2
Karston Cove 3'd Addition; and
WHEREAS, City staff has reviewed the submitted applications and submission documents
and has prepared a planning report dated September 8, 201 6; and
WHEREAS, the Planning Commission held a public hearing on September 13, 2016 to
consider the application, the planning report, and take public testimony; and
WHEREAS, upon conducting the public hearing, the Planning Commission requested
additional information and continued the public hearing, pending the City Attorney's opinion
that the continuance would not be an issue for the development agreement deadline; and
WHEREAS, the City Attorney has issued a September 15, 2016 opinion requesting the City
Council act on the application on October 3, 2016 to allow time for subsequent legal actions; and
WHEREAS, the City Council met on October 3, 2016 to consider the application and held a
public hearing to consider the vacation of select easements in conjunction with the Karston Cove
4th Addition; and
WHEREAS, upon review of the application information, the request for Council action, the
September 8, 2016 planning report, and public testimony, the City Council moves to approve the
development application and vacate select easements associated with Karston Cove 4th Addition.
NOW, THEREFORE, BE IT RESOLVED that the City Council of Albertville, Minnesota
hereby approves the amendment to the CUPIPUD allowing the vacation of 29 townhome lots and
one common lot, the Karston Cove 4th Addition preliminary plat, the Karston Cove 4th Addition
final plat, and vacation of select easements associated with Karston Cove 4th Addition subject to
the following conditions being met:
1. The City retains the option to require the future development on out of A Karston Cove
4th Addition to join with the existing Karston Cove HOA on the north side of 64th Street
Page 1 EXHIBIT D
Agenda Page 44
City of Albertville
Resolution No. 2016-
Meeting of October 3, 2016
Page 2
through a revised PUD development agreement to be recorded against the out of A
property with the future final pat. Notwithstanding this reservation of rights, the City
acknowledges that it may not impose any obligation on the developer to add the future
lots to the existing Karston Cove HOA unless the Declaration establishing the HOA has
been modified, on or before the time of final plat approval, to allow for the addition of
the outot A land to the Homeowner's Association.
2. The City finds that the drainage and utility easements dedicated on the Karston Cove 3ra
Addition plat (but excluding those easements dedicated on the first plat of Karston Cove)
are no longer needed for public purposes and that it is in the interest of the public to
vacate said drainage and utility easements.
3. The City vacates the drainage and utility easements shown on the Karston Cove 3rd
Addition plat, provided the 4th Addition final plat is revised to preserve as drainage and
utility easements all drainage and utility easements originally dedicated on the first plat
of Karston Cove Said easements shall be subject to the review and approval of the City
Engineer prior to recording the final plat. The vacation of said easements shall be
effective upon the recording of the Karston Cove 4th Addition plat.
4. The City approves the preliminary and final plat of Karston Cove 4th Addition, subject to
the conditions set forth in the City Planner's report dated September 8, 2016, including
execution of a development agreement as set forth below.
5. The Developer shall be required to install sidewalk per approved plans, boulevard
grading and restoration to a turf condition by June 30, 2017 as a condition of final pat
approval, unless Developer submits a completed preliminary plat application for the site
by June 30, 2017, in which case the June 30, 2017 installation date shall be automatically
extended to June 30, 2018.
6. The applicant enters into a development agreement with the City that includes the
aforementioned conditions of approval, addresses the issues identified in the RCA for this
matter, and meets the approval of the City Attorney. The development agreement shall
be recorded against the property with the final plat.
7. Upon execution of the development agreement and recording of the plat, the City shall
release the monies it holds in escrow from the proceeds of the letter of credit for Karston
Cove 3rd Addition, except for an amount sufficient to cover 125% of the cost of the
installation of sidewalk, boulevard grading and restoration and the anticipated expenses
of the City Attorney, Planner and Engineer related to Karston Cove 3rd Addition and
Karston Cove 4th Addition. The City Engineer shall determine the amount of escrow to
be held for the installation of such items and the City Finance Director shall determine
the remaining amount of escrow to be held to cover anticipated City expenses.
2
Agenda Page 45
City of Albertville
Resolution No. 2016-
Meeting of October 3, 2016
Page 3
Adopted by the City Council of the City of Albertville this 3rd day of October, 2016.
Jiian Hendrickson, Mayor
Kimberly A. Olson, City Clerk
3
Agenda Page 46
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Peal People. Peal Solutions.
11/30/2017
Adam Nafstad, P.E.
City Administrator/PWDICE
5959 Maine Ave NE, Po Box 9
Albertville, MN 55301
RE: Hunters Lake Water Budget Analysis
City of Albertville
Project No.: C 13.114803
Dear Mr. Nafstad,
2035 County Road D East
Maplewood, MN 55109-5314
Ph: (651) 704-9970
Pax: (651) 704-9971
Bolton-Menk.corr
Bolton & Menk, Inc. has completed a water budget for Hunters Lake. The waste water treatment plant
currently discharges its effluent into Hunters Lake. The study analyzed the current water budget for the
lake and the long term impacts of removing the effluent stream. Also, water quality and fish impacts
were discussed.
If you have any questions or comments regarding this study please feel free to reach me at thnol. @, bol.ton-
nenk.co n. or by phone at (651) 704-9970 at your convenience.
Sincerely,
Briton & Menk, BIn .
Timothy J. Olson, PE, CFM
Water Resource Project Manager
Name: Hunters Lake Water Budget
Date: 11/30/2017
Page: 1
HUNTERS LAKE WATER BUDGET ANALYSIS
Executive Summary
The primary goal of the analysis was to estimate the effect of removing the waste water treatment plant
(WWTP) effluent stream from the lake and to quantify the effect it will have on the Lake's water surface
elevation. A secondary goal of this study was to determine whether or not additional storm water runoff
would mitigate the loss of flow from the waste water treatment plant (WWTP). The final goal was to
quantify the effects of the WWTP effluent on the water quality of Hunters Lake. The following memo
summarizes the approach taken and the results of the analysis.
In general, lakes have both naturally occurring seasonal water surface elevation changes as well as long
term water surface elevation changes. The results of the study indicate that removing the effluent from
the WWTP will return the lake to its natural elevation variation. Upon removal of the effluent stream, the
lake water surface elevation is estimated to be 6 inches lower than its current average elevation. Removal
of the WWTP effluent from the lake will likely allow a total ice surface to form in the winter, as well as
periodic winterkills of carp and other fish. Reducing the carp populations will be beneficial to the water
quality of the lake by reducing resuspension of fine sediment and nutrients in the bottom substrate of the
lake as well as promoting the natural regrowth of rooted aquatic vegetation. This combination will also
improve dissolved oxygen concentrations, support the natural lake circulation process and reduce or
eliminate the anoxic conditions that are causing odor issues. Removal of the WWTP effluent coupled
with carp removal and revegetation will improve water quality of Hunters Lake.
In the future, if it is determined that lake levels are too low, an outlet structure could be constructed to
better control the lake level. Additional automated outlet controls and lake level monitoring could be
considered to help the City monitor lake levels and make changes on the fly as needed to ensure lake
levels remain consistent. Overall, the restoration of natural water -level regimes is likely to lead to
enhancement of water quality and biodiversity of the lake.
This report includes the following contents.
a Water Budget Approach
a Methodology
o Model Results
a Future Contributions
a Carp
a Water Quality
a Odor/Stagnant Water
a Conclusions & Recommendations
H: \ALS T\C 131148 0 3 \2_Preti minary\C_Reparts\Water_Sudget_Mema_ I 13 0 2 0 17.da cx
B o U, o n &. Munk icy arl e q u ac . C3ppCyf"fit. nity k:,"mp1,oyer,
Name: Hunters Lake Water Budget
Date: 11/30/2017
Page: Z
Water Budget Approach
Three separate water budgets were developed to analyze the effects of the WWTP effluent on the water
levels of Hunters Lake. A lake water budget is a computation of the inflows, outflows and change in
storage volume over time. The first water budget was completed for School Lake, directly upstream of
Hunters Lake, to determine the outlet flow conditions to Hunters Lake. The second two water budgets are
both for Hunters Lake and compare the water surface elevations for the same time period both with and
without the effluent from the WWTP.
The water surface of School Lake is approximately 70 acres at the normal water level with a 1200 acre
watershed. The outlet control structure for the lake holds the normal water level (NWL) at approximately
946.7ft (NAVDSS). Under typical conditions, runoff from the watershed will flow through School Lake
and into Hunters Lake. However, during dry periods, the water in School Lake may drop below the outlet
elevation and not contribute to Hunters Lake.
Hunters Lake lies directly downstream of School Lake and has a contributing watershed area of
approximately 400 acres. The NWL established by the outlet control structure is approximately 946ft
(NAVDSS) creating a 74 acre shallow lake. The outlet from Hunters Lake is a 27-inch diameter
corrugated metal pipe (CMP) culvert placed in the channel downstream under Lakewood Drive.
Methodology
For this study, it was assumed that the only inflows into the Lakes are from storm water runoff from the
contributing watershed area, the rain falling directly onto the lake surfaces, and the effluent from the
WWTP. Outflows from the lakes include surface outflow and evaporation from the lake surface. Inflow
and outflow of groundwater is expected to be a small component of the total water budget for this shallow
lake and has been disregarded in this analysis. Runoff from the contributing watershed was calculated
using the SCS methodology described in the NRCS TR-55 publication. A table of the total watershed
areas and the composite curve numbers are summarized in Table 1.
Table 1 Summary of Watershed Characteristics
istics
Hunters Lake 334 83
It was assumed that any precipitation that fell on the watersheds between December 1 st and March 31 st
would not discharge until April 1 st. This was done to simulate the effects of snow and ice on the system
and the recharge of the lake due to snowmelt. Any accumulated precipitation was discharged evenly
across April 1 st-April 3rd to approximate a 3 day snowmelt.
Two sources of water loss were considered in this water budget. The first loss considered was due to
evaporation during periods of open water. It was assumed that the lakes would freeze over on December
1st and remain frozen through April Is'. Mean monthly evaporation rates for the lakes were derived from
NOAA Technical Report NWS 34.
The second loss is the controlled water outlets. A stage vs. discharge rating curve was developed for each
pond's outlet using Autodesk's Storm and Sanitary Sewer Analysis software. These rating curves were
then brought directly into the water budget model and used to determine the average daily flow out of the
H: \ALS T\C 131148 0 3 \2_Preli minary\C_Reparts\Water_Sudget_Mema_ I 13 0 2 0 17.da cx
B o U, o n &. Munk icy arl e q u ac . C3ppCyf"fit. nity k:,"mp1,oyer,
Name: Hunters Lake Water Budget
Date: 11/30/2017
Page: 3
lake based on that day's average water surface elevation. For School Lake, any water leaving the system
through the outlet was routed as an additional flow into Hunters Lake.
Lake DVscire Dating Curve
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There is evidence that the current water surface elevations in Hunters Lake are higher than the modeled
elevations. Survey data of the lake indicates that the current water surface elevation is approximately
947.5ft. This elevation is contradictory to previous reports and survey data which indicate that the outlet
elevation of Hunters Lake is at 945.9ft and that the designed looyr flood elevation for the lake is at
947. Sft. This discrepancy could be caused by several factors such as a backwater effect of the downstream
culvert crossing or blocked channels or culverts. Further field inspections and surveys should be
considered to determine the cause of this increase as it may pose a risk to flooding nearby properties.
As described above, ground water exchange was not considered in the water budget analysis. It was
assumed that the groundwater inflows or losses between the existing and proposed conditions would be
small and not changed substantially if the WWTP effluent discharge was removed and thus not
considered in the water budget.
The model simulates lake level responses using rainfall data from January 1st 2008 to December 315t
2012. This range was chosen after analyzing 77 years of rainfall data to determine the average yearly
rainfall depth. The goal of this approach was to provide an "apples to apples" comparison of the
theoretical lake levels using rain gage data from 2008-2013 from a local rain gage.
The analysis shows that the average rainfall depth is 29.9 inches of precipitation with a standard deviation
of 6 inches. 2008 was a relatively dry year with an annual precipitation depth of only 24.76 inches, falling
on the low side of the typical rainfall spectrum. In contrast, Zo 10 had an annual rainfall depth of 35.95 in.
Table Z below shows the entire study periods annual rainfall depth.
H: \ALB T\C 131148 0 3 \2_Preti minary\C_Reports\Water_Budget_Mema_ 113 0 2 017.do cx
B o U, o n &. Munk icy arl e q u ac . C3pp[7f"fit. nity k:^mp1,oyer,
Name: Hunters Lake Water Budget
Date: 11/30/2017
Page: 4
year depth (in)
.008
2436
2.00
28,57
.010
5. 5
2,011
29.E
2.0.12
29.,63
Average
29.9
d.. Cep,
6.,0
Model Results
The water budget model indicates that the removal of flow from the WWTP will decrease the typical
water surface elevation in Hunters Lake. on average, the lake level will decrease by approximately 6
inches. Along with this, the lake is likely to see greater seasonal fluctuations as there will no longer be the
constant flow from the WWTP to mitigate periods of low rainfall. The effluent flow from the WWTP
essentially offsets the rate of evaporation during the drier summer months.
Periods of reduced rainfall (ex. drought in 2008) or years with smaller rain events (ex. fall of 2012) will
impact the lake elevation more heavily and the water surface will likely drop by approximately 1 ft.
Figure Z displays is a data plot of the daily water surface elevation over the period of study. The bottom
elevation of the lake was measured at an elevation of 942.65ft NAVD88 indicating that the lake retained a
minimum of 3 feet of depth throughout the study period.
Future Contributions
An additional goal of this study was to determine whether or not adding runoff, by diverting land from
adjacent watersheds, to Hunters Lake would help mitigate the removal of the WWTP effluent. Table 3
below compares the minimum, average, and maximum daily water surface elevation in Hunters Lake for
the existing and proposed conditions. All of the proposed watershed conditions are assuming 100%
directly connected impervious area.
i
ii iii� iim
ii�i
IIIAverage"',
'�C�Max
E. isti n
45. 7
4 .1
946.46
o WWTP
94-4.99
945.65
946.32
+2 5a c
45.1
45. 5
946.45
+50ac
945.2
945. 1
4 .,52
+ 5a
4.5.27
45. .5
946.6.E
+100a
45.
45.
4 .74
The additional flow to the watershed does help to mitigate the reduction of the average lake surface
elevation. However, as shown in the Figure Z below, it does not reduce the seasonal fluctuations.
H: \ALS T\C 131148 0 3 \2_Preti minary\C_Reparts\Water_Sudget_Mema_ 113 0 2 017.da cx
B o U, o n &. Munk icy arl e q u ac . C3pp[7f"fit. nity k:^mp1,oyer,
Name: Hunters Lake Water Budget
Date: 11/30/2017
Page: 5
Furthermore, any additional area added above approximately 35ac will increase the peak water surface
elevations of the lake and may increase the risk of flooding of nearby properties. Any additions to the lake
should be evaluated in detail risks of flooding on adjacent and downstream properties.
Ater Surface Edevation Comparison 2
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Removing the effluent from the WWTP will return the lake to its natural elevations, which on average is
estimated to be 6 inches lower than its current seasonal levels. In the future, if it is determined that lake
levels are too low, an operable outlet structure could be considered to provide additional control of the
lake level.
Carp
Carp, an invasive fish, are presently flourishing in Hunters Lake. Carp are a bottom feeding fish which
root up and erode the lake bottom sediments and re -suspend phosphorous in the water, often leading to
increased turbidity, algae blooms, and reduced transmissivity of sunlight needed for submersed rooted
vegetation to grow. Carp also destroy rooted aquatic vegetation which provides habitat and helps to keep
sediments in place.
Removal of carp can be beneficial to the lake ecosystem and improve the quality of the lake for wildlife.
Control of carp populations is crucial for stabilizing bottom sediment and improving water clarity. It is
expected that by removing the WWTP effluent that the lake surface will freeze in the winter, which may
reduce the dissolved oxygen concentration to less than Z mg/1-where fish such as carp will be stressed,
suffocate and die.
Given the lake is relatively shallow, a full ice cover may result from removal of the warm WWTP
effluent. The carp population in Hunters Lake is a concern in terms of long term water quality,
H: \ALS T\C 131148 0 3 \2_Preti minary\C_Reparts\Water_Sudget_Mema_ I 13 0 2 0 17.da cx
B o U, o n &. Munk icy arl e q u ac . C3pp[7f"fit. nity k:'^mp1,oyer,
Name: Hunters Lake Water Budget
Date: 11/30/2017
Page: 6
resuspension of accumulated sediment and pollutants tied to the sediment and lake vegetation. Therefore,
a partial or complete winterkill would reduce the carp population (at least in the first year) and give the
lake an opportunity to "reset". If carp and other rough fish can be controlled, Hunters Lake will likely see
improved rooted aquatic vegetation, improved water quality and clarity, and improved fish and wildlife
habitat for native species.
Water Quality
A P8 model of the Hunters Lake watershed was completed to estimate the current phosphorus (P) loading
in Hunters Lake. Since bathymetric analysis was not performed on School Lake, the total lake storage
volume and solids and phosphorus treatment capacity is unknown. It is assumed that School Lake
contributes phosphorus to Hunters Lake. Based on similar land use, it is assumed that the School Lake
watershed contributes phosphorus at the same rate as the Hunters Lake watershed based on area. The
School Lake watershed is 3.5 times larger than the Hunters Lake watershed and is assumed to contribute
3.5 times more phosphorus.
The typical loading rate from the WWTP is 0.355mgIL. Table 4 below illustrates the total reduction in P
loading that can be expected in Hunters Lake by removing the WWTP effluent.
Hunters Lake Watershed
398.8
Ib/yr
School Lake Watershed
1395.8
Ib/yr
WWTP
930.E
Ib/yr
Reduction
40.0
%
The water quality of Hunters Lake will likely improve due to the removal of the WWTP effluent. Also, it
is likely that the removal of the WWTP effluent into Hunters Lake will cause some winterkill of the carp
population. Removal of the warm effluent will allow the lake surface to freeze in the winter months,
eliminating a warm area with open water and aeration where the carp migrate for refuge.
Odor/Stagnant Water
Removing the WWTP effluent stream from the lake will reduce the constant outflow from the lake,
especially during periods of low rainfall. Many Minnesota lakes have no outflow during parts of the year,
so constant outflow is not required for good water quality. In open -water periods, the shallow Hunters
Lake will likely be well -mixed by winds and aerated so that objectionable odors are unlikely. Odor
problems more often result following anoxic conditions when hydrogen sulfide is produced from organic
decomposition. If over -winter oxygen levels become an issue the City may want to explore options in the
future to aerate the lake. Aeration can be a complex issue that would require further study/analysis to
determine the exact cause and effect of actions that could be taken to address this subject.
Conclusions & Recommendations
In conclusion, the removal of the WWTP effluent will result in a seasonal water level drop of
approximately 6 inches in Hunters Lake. This drop will vary and will be more impacted by seasonal
rainfall variations. The loss of the WWTP effluent may be partially mitigated by increasing the watershed
area contributing to the lake. However, lake levels will still experience seasonal fluctuations.
H: \ALS T\C 131148 0 3 \2_Preli minary\C_Reparts\Water_Sudget_Mema_ I 13 0 2 0 17.da cx
B o U, o n &. Munk icy arl e q u ac . C3ppCyf"fit. nity k:',"mp1,oyer,
Name: Hunters Lake Water Budget
Date: 11/30/2017
Page: 7
The following recommendations describe some opportunities for the City to learn more about Hunters
Lake and develop long term approaches to lake level control and improved water quality.
M Removing the WWTP effluent will impact seasonal lake elevation variations but will restore the
lake to its native water budget. If the reduced lake elevation is a concern, the City could consider
a manual or automated gate structure at the outlet to help maintain a more consistent water
surface elevation during dry periods.
M Hunters Lake has a significant carp problem. Allowing ice to form may result in periodic
winterkills in the lake, reducing the carp population and allowing for natural rooted vegetation to
reemerge, along with better water clarity, and improved fish and wildlife habitat for native
species.
M The removal of WWTP effluent will substantially reduce the phosphorus inflow which, in turn,
mitigates algae growth. Reduced algae will reduce the oxygen consumed by the algae and
reserve oxygen for native lake vegetation and fish species. These simple best practices will
reduce the need for additional mechanical aeration, or other more costly facilities to improve
water quality.
M Removing the WWTP effluent stream from the lake will reduce the constant outflow from the
lake, especially during periods of low rainfall, but constant outflow is not required for good water
quality. In open -water periods, the shallow Hunters Lake will likely be well -mixed by winds and
aerated so that objectionable odors are unlikely.
M The City currently cleans the outlet channel and performs regular maintenance of the culvert
outfalls. These measures should continue to ensure the seasonal water elevations are known and
consistent
M Hunters Lake is a public water lake which has a published ordinary high water level (OHWL).
The OHLW is not the 1 oo-year flood level, but rather the water surface elevation that is
maintained for a relatively long period of time. It is also known as the "ordinary pool elevation".
The OHLW for Hunters Lake could be analyzed for accuracy and changed, if needed, to align
with long term lake management goals.
M Hunters Lake is impaired for nutrients, but does not have a completed Total Maximum Daily
Load (TMDL) study. The TMDL will identify the significant pollutant inflow points along the
lake, including the contribution from the WWTP, and identify the pollutant reductions required to
return the lake to an acceptable nutrient level. Ultimately, an implementation plan will be created
to help prioritize projects and establish a timeline for restoring the lake to an acceptable water
quality. The City should thoroughly review the TMDL when it is published to ensure that the
implementation plan includes the City's long term goals for the lake.
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MR II,,,, alke Wateir Budget Aina�lysiis MR II,,,, alke Bathyirwietidcs
City of Albertville
October 2017
BOLTC] N
& MENK
Real People. Real Solutions.
M RA d I alke Wateir Budget Aina�lys�is M RA d I alke Bottoirn Coirwilposi'ition
City of Albertville
October 2017
DBOLTC] N
& MENK
Real People. Real Solutions.