HomeMy WebLinkAbout1995-10-12 Barr Engineering Memo to VBWD Re Cloverdale Lake FloodingTo:
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VBWD Managers
From: Randy Peterson
Subject: Cloverdale Lake Flooding
Date: October 12, 1995
Project: 23/82- 016RDP06
Barr Engineering Co.
Memorandum
At the request of the Managers, we have performed a general review of the flooding situation
and have addressed potential interim and future solutions. This memorandum discusses the
characteristics of the Cloverdale Lake watershed and recent precipitation data, potential interim
flood control measures, and future flood control measures. Nearly all of the information in this
memorandum is included in the District's Water Management Plan.
Cloverdale Lake Watershed & Recent Pr Data
Cloverdale lake has a 670 acre tributary watershed. Over 50 percent of the watershed is
developed to date. The previously established normal elevation for the lake is El. 899.0, with an
Ordinary High Water (OHW) equal to El. 900.7 and a 100 -year flood elevation of 908.5. Elevation
908.5 is the surface overflow elevation from Cloverdale to McDonald Lake. In 1993 Cloverdale
Lake rose from approximately Elevation 897 to 903. Based on water levels since then, little to no
seepage has occurred from the lake. Asa result of continued above average precipitation in 1994
and 1995 the lake has been between Elevation 905 and 906 since August, 1995.
The Stillwater Area High School and currently undeveloped commercial areas immediately
north of the school are approximately 134 acres (20 percent) of the total tributary area. Under full
development conditions, the amount of impervious area in this 134 acre area is approximately
equal to the total amount of impervious area in the remainder of the watershed (67 acres).
Attached are two figures that compare monthly (30 -year normal) precipitation values at the
Mpls- St.Paul Airport to monthly precipitation at Chuck Taylor's rain gage in Lake Elmo. Figure 1
shows two graphs, the upper one showing the correlation between Mpls. and Lake Elmo actual
data, and the lower graph comparing Lake Elmo data to Mpls -St. Paul normal precipitation.
Figure 2 is a larger version of the lower graph on Figure 1 with the volume of precipitation above
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Cloverdale Lake Flooding
normal as shaded. Flooding at the Sunnybrook area from 1993 to present is also an indication of
the above normal precipitation pattern that has occurred beginning in 1993.
Potential Interim Flood Control Measures
The Managers received a copy of a letter sent to Joe Anderlik, City Engineer for the City of
Oak Park Heights, requesting temporary flood easements on two ponds within the Stillwater High
School property. The four property owners on the south side of the pond are also being contacted.
Storing additional runoff at these two ponds is the most viable and inexpensive temporary
measure available. Construction of the proposed modifications is expected to range from $1,000 to
$2,000 dollars.
A third ponding area identified by Paul Bischoff is located adjacent to the high school property
and was constructed as part of the Kern Center development. This ponding area is on the east
side of Highway 5, and is too small to warrant the necessary costs to route water to this pond.
The ponding area on the west side of Highway 5 is sized for more developed area than currently
exists. Piping water to this area would likely involve use of an existing pipe under Highway 5,
previously blocked off by MnDOT when Highway 5 was expanded. This option is possible but
would involve significant coordination and easement acquisitions.
Future Flood Control Measures
The MnDOT is planning expansion of Highway 5 from about 55th Street north to Highway 36.
This work is expected to include lowering the Highway 36 interchange by approximately 6 feet,
expanding this section to 4 lanes with a tapered section south of 55th Street, and upgrading
drainage facilities. Most of this area is currently not tributary to Cloverdale Lake and is not
proposed to be tributary after completion of the proposed Highway expansion.
The third Figure attached is a map of a portion of the District including Sunnybrook,
Cloverdale, McDonald, Downs, and Horseshoe Lake as well as Goetschel Pond. The water
management plan included consideration for a proposed pipe system connecting all or some of
these lakes into Horseshoe Lake. This discharge would most likely need to occur at off -peak times
such the fall or winter months.
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Cloverdale Lake Flooding
Consideration for this type of main stem system would require a significant study to determine
the feasibility of such a system. This item is included in the proposed capital improvements
program and could be considered for 1996. Determination of a revised Goetschel Pond flood level,
done as part of development proposed for that watershed, will be completed this year. The
Goetschel Pond area could supply additional flood storage. However, an eventual outlet to these
landlocked areas would be the best long -term solution to address future unacceptable flood level
variations.
Other potential long -term solutions could include piping or pumping from Cloverdale Lake to
Goetschel Pond or some combination of providing outlets from the landlocked areas previously
mentioned. To determine the most cost effective option for Cloverdale Lake and other the
landlocked areas described, the Managers should consider undertaking a more detailed study as is
mentioned above and in the District's water management plan.
I O.(X
Mpls-St.Paul VS Lake Elmo Precipitation
Actual Monthly Totals 1993 to 19
MPLS-ST.PAUL –° -- LAKE ELMO
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Jan -93 Mar - 93May- 93Jun -93 Aug -93 Oct -93 Dec -93 Feb-94 Apr -94 Jun -94 Aug-940ct-94 Dec -94 Feb -95 Apr -95 Jun -95 Aug -95 Oct -95 Dec -95
Date
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Date
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Mpls- St.Paul NORM VS. Lake Elmo ACTUAL
Monthly Totals 1993 to 1995
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Lake Elmo Total 93-95 = 103 inches
, Mpls Normal (3 yrs) = 85
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3 Months
1 — MPLS- ST.PAUL AVG "°" -"' LAKE ELMO ACTUAL Above Avg. Precip
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