HomeMy WebLinkAboutAnnexation Area Surface Water Management Plan Dec 19951
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ANNEXATION AREA
SURFACE WATER
MANAGEMENT PLAN
'
OAK PARK HEIGHTS, MN
BONESTROO, ROSENE, ANDERLIK & ASSOCIATES
'
DECEMBER 1995
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JA Bonestroo
Rosene
MEM Anderlik &
" Associates
Engineers & Architects
December 23, 1995
Bonestroo, Rosene, Anderlik and Associates, Inc. Is an Affirmative Action /Equal Opportunity Employer
Otto G. Bonestroo. P.E.
Robert W. Rosene. RE.
Joseph C. Anderllk. PE.
Marvin L. Sorvala. P E.
Richard E. Turner. P.E.
Glenn R. Cook. P,E.
Thomas E. Noyes. P.E.
Robert G. Schunichl. P.E.
Susan M. Eberlin. C.P.A.•
• Senior Consultant
Howard A. Sanford, P.E.
Keith A. Gordon., P.E
Robert R. Pfefferle, P.E.
Richard W. Faster, P.E.
David O. Loskota, P.E.
Robert C. Russek, A.I.A.
Jerry A. Bourdon, P.E.
Mark A. Hanson, P.E.
Michael T. Rautmann. P.E.
Ted K. Field, P.E.
Thomas R. Anderson. A.I.A.
James R. Rosenmerkel, P.E.
Donald C. Burgardt. RE.
Thomas A. Syfko, P.E.
Frederic J. Stenborg, P.E.
Ismael Martinez, P.E.
Michael P. Rau, P.E.
Thomas W. Peterson. P.E.
Michael C. Lynch, P.E.
James R. Maland. P.E.
Jerry D. Pertzsch. PE.
Scott 1, Arganek. P.E.
Kenneth P. Anderson, P.E.
Mark R. Rafts. P.E.
Mark A. Skip, P.E.
Gary W. Marlon. P.E.
Paul J. Gannon, AI.A.
Daniel J. Edgerton, P.E.
A. Rick Schmidt, P.E.
Data A. Grave, P.E.
Philip J. Caswell, P.E.
Mark D. Wallis, P.E.
Mlles B. Jensen, P.E.
L Phillip Gravel. P.E
Karen L. Wiemeri, P.E.
Gary D. Krlstofila, P.E.
Brian K. Gage. P.E.
F. Todd Foster, P.E.
Keith R. Yapp. P E.
Douglas J. Benoit. P.E.
Shawn D. Gustafson. P.E.
Cecil. Olivier, P.E.
Kent J. Wagner, P.E.
Paul G. Heuer. P.E.
John P. Golder. I.E.
Dan D. Boy.. I.E.
Jeffrey J. Ehlednger. P.E.
Joseph R. Rhein, P.E.
Lee M. Mann. P.E.
Charles A. Erickson
Leo M. Pawelsky
Harlan M. Olson
Agnes M. Ring
James F. Engelhardt
Honorable Mayor & Council Members
City of Oak Park Heights
14168 57th Street North
Stillwater MN 55082 -2007
' Re: Annexation Area Surface Water Management Plan
Our File No. 55121
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Dear Mayor & Council Members:
Submitted herewith is the Surface Water Management Plan for the portion of Oak Park Heights west
of Oakgreen Avenue, hereinafter referred to as the "annexation area." The information presented in
this report is intended to provide a basis for the construction of a cost - effective trunk stormwater
system for this area.
I. Introduction
This report presents a Surface Water Management Plan for the annexation area of Oak Park Heights.
This area, shown in Figure No. 1, is defined by Oakgreen Avenue on the east, State Highway 36 on
the north, State Highway 5 on the west, and the natural drainage boundaries along the city limits on
the south.
The report contains a discussion of the hydrologic and water quality modeling, including assumptions
about design storms and land use. It also presents cost estimates to pay for the proposed facilities.
The proposed storm sewer system is presented in Figure No. 1, and detailed design information is
contained in the report tables.
H. System Analysis
Physical Environment and Land Use
The annexation area is at the headwaters of three watersheds. The northern portion of the area, in
the Browns Creek Watershed, flows north under Highway 36. The southeastern portion of the area,
in the Middle St. Croix Watershed, flows northeast and southeast. The southwestern portion of the
area, in the Valley Branch Watershed, flows south to Cloverdale Lake.
2335 West Highway 36 K St. Paul, MN 55113 a 612 - 636-4600
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' The area is gently rolling, with a number of landlocked depressions. The soils in the area are
generally well- drained. Many of the depressions contain ponds and wetlands. Land cover consists
' of agricultural area, open space, forested area, commercial development along Highway 36, the
Stillwater High School, and single - family residential area. Long -term land use was assumed to be
' commercial north of 58th Street North, and single - family residential plus the high school south of
58th Street North.
' Hydrologic Analysis
Hydrologic modeling was performed to design the trunk storm sewer system. The trunk system is
' defined as the stormwater detention ponds plus the storm sewers necessary to connect them with the
various outlets from the annexation area. The detention ponds were designed to store and release
the runoff from a 100 -year storm event without flooding of adjacent buildings.
1 Both the 5.9 -inch, 24 -hour rainfall and the 7.2 -inch, 10 -day runoff were investigated, with the more
critical high water level used for each pond. In the majority of the ponds, the 24 -hour rainfall event
' proved to be more critical. We recommend a minimum 2 -foot freeboard from the pond high water
level to the lowest opening in adjacent buildings.
t The hydrologic modeling software HydroCAD was used for the modeling. Drainage areas were
determined from 2 -foot contour maps. Pond normal water levels were set to match existing
' conditions to the greatest extent possible. As -built or proposed development plans were used where
appropriate. The model was used to size pond outlet facilities and compute pond high water levels,
storage volumes, and peak outflows.
' The proposed trunk storm sewer system is presented in Figure No. 1. Drainage areas are given in
Table 1. Detention pond data are presented in Table 2.
' Water Quality Analysis
' A water quality analysis was performed to ensure that the stormwater leaving the annexation area will
be of good quality. A goal of less than 200 parts per billion (ppb) of phosphorus in the stormwater
leaving the area was selected as a design criterion, as this corresponds to typical natural
' concentrations.
Because a number of the existing depressions and wetlands have ponded water, these were
' incorporated into the water quality system. In other areas with less capacity for pollutant removal,
water quality ponds are proposed to be excavated.
' The proposed water quality ponding system is shown in Figure No. 1 and is conceptual in nature and
not necessarily to scale. Detailed information on the water quality ponds is presented in Table 3.
' Ponds 11, 21, 31, and 42, representing flows out of the study area, all have outflow phosphorus
concentrations less than 200 ppb.
' Four ponds (13a, 13b, 15a, and 32a) are proposed to be excavated strictly for water quality purposes.
Four ponds (15, 22, 23, and 44) are proposed to be excavated for both water quantity and quality
Oak Park Heights Annexation Area Surface Water Management Plan 2
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' purposes. The remainder of the ponds have already been designed or constructed (11, 12, 21, 42,
' and 43) or rely primarily on existing, natural contours. A grading plan has been submitted for Pond
15a, but this is for a small pond to handle local runoff only. This Surface Water Management Plan
calls for Pond 15a to be expanded in the future to handle more regional flows.
' The 12 -inch outlet from Pond 31 has been designed to maximize storage and water quality treatment.
The contour maps indicate a number of trees in this area. Without further field survey information,
it is difficult to estimate the elevations of the lowest trees. If necessary, it would be possible to lower
the normal water level in Pond 31 from the proposed 903 to about 901 to prevent flooding of
adjacent trees. This reduction in normal water level would not have a significant effect on the water
' quality leaving the pond.
III. Cost Estimates
' Cost estimates for the proposed facilities were developed and are presented in Table 4. The estimated
total project cost for the storm sewer system is $894,200, including engineering, administration,
' interest during construction, and contingencies. Land and easement acquisition costs are not
included. The costs are based on 1995 construction costs and can be related to an ENR Index of
Construction Costs of 5,432 (June 1995). Future changes in the index are expected to reflect fairly
accurately cost changes in the proposed facilities.
' IV. Cost Allocation
Table No. 1 identifies 685 acres of land within the study area of which 260 acres has been platted
' and/or developed and assigned area charges. After subtracting land consumed in collector street and
highway right -of -way and deducting undevelopable land consisting of steep slopes, wetlands and
ponds, the resulting assessable land is approximately 320 acres broken down as follows:
' Low Density 230 acres
High Density 40 acres
' Commercial - Industrial 50 acres
If the existing storm sewer area charges are applied to the assessable land area, the following revenue
will be generated:
' Low Density 230 ac x 2,405.00/ac $553,150.00
High Density 40 ac x 3,935.00/ac 157,400.00
Comm. -Ind. 50 ac x 4,650.00/ac 232.500.00
' Total Revenue $943,050.00
Based on this analysis, the charges currently in place should fund the trunk storm sewer and ponding
' requirements defined for the study area.
The above analysis does not provide for any costs for land acquisition. Ponding areas are generally
' dedicated as a part of the development process because they are normally located in or around
existing wetlands. However, because there has been some objection to dedicating land for regional
' Oak Park Heights Annexation Area Surface Water Management Plan 3
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ponding, it is suggested that the following additional charge for storm water ponding be initiated in
the event land is not dedicated without cost.
Land Use Ponding Charee
Low Density $1,600.00 /acre
High Density $2,400.00 /acre
Commercial- Industrial $3,200.00 /acre
V. Summary
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This report presents a proposed trunk stormwater system for the annexation area of Oak Park
Heights. The system, shown in Figure No. 1, includes storm sewers and stormwater ponds for both
flood control and water quality purposes. Tables 1 to 3 present design information on the system.
Cost estimates are presented in Table 4. The total estimated cost of the proposed system is $894,200.
VI. Recommendations
' It is recommended that the City adopt this Surface Water Management Plan and use it for the design
and implementation of surface water drainage facilities to serve the study area west of Oakgreen
Avenue. It is further recommended that the current system of area charges be continued and that an
' additional charge be initiated to encourage land dedication for ponding and/or to secure funding for
land acquisition.
' Respectfully submitted,
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BON I;STl2Q0 ROOS ANDERLIK & ASSOCIATES, INC.
Daniel J. E A d / g J rtC On, P. .
I hereby certify that this report was prepared by me or
under my direct supervision and that I am a duly
Registered Professional Engineer under the laws of the
State "innesota-
JosepWC. Anderlik, RE
Date: December 23, 1995 Reg. No. 6971
Vak Park Heights Annexation Area Surface Water Management Plan 4
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TABLE I. DRAINAGE AREAS.
Area
Designation
Drainage
Area
(acres)
111
59
112
20
121
29
131
33
132
26
141
64
151
19
152
19
211
8
221
23
231
8
241
13
311
55
321
63
331
32
341
11
351
18
421
81
431
26
441
45
451
19
461
14
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TABLE 2. DETENTION POND DATA.
Pond #
Tributary Area (acres)
Normal
Water
Level
High
Water
Level
Storage
Volume
Above NWL
ac -ft
Pond Peak
Outflow
cfs
Direct
Ponded
Total
11
79
190
269
917.0
923.5
29.4
35.5
12
29
0
29
933.2
936.8
4.6
5.5
13
59
0
59
927.0
930.0
12.9
2.7
14
64.
0
64
926.0
930.8
11.6
5.5
15
38
29
67
918.0
924.1
6.4
50.3
21
8
44
52
915.6
918.6
0.5
21.2
22
23
21
44
928.0
933.3
4.2
6.4
23
8
13
21
931.0
935.4
2.0
3.9
24
13
0
13
932.9
935.9
1.7
4.2
31
55
124
179
903.0
908.2
45.8
4.3
32
63
0
63
911.0
913.3
9.4
17.1
33
32
29
61
904.5
908.3
13.8
2.9
34
11
18
29
912.0
918.1
1.7
6.8
35
18
0
18
926.0
928.5
2.6
5.4
42
81
104
185
915.0
923.5
33.5
12.0
43
26
45
71
924.0
929.1
4.2
45.5
44
45
0
45
931.0
934.9
13.2
7.2
45
19
14
33
934.0
935.2
4.5
3.1
46
14
0
14
935.0
936.0
2.6
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TABLE 3. WATER QUALITY POND DATA.
Pond #
Direct
Tributary
Area
(acres)
Normal
Water
Level
Pond Area
@ NWL
(acres)
Wet
Volume
(ac -ft)
Outflow
P -conc.
( b)
Total
Efficiency
M
11 3 -cell
59.0
917.0
2.82
10.3
192
68
12
29.0
933.2
1.09
2.0
232
51
13 (2 -cell)
34.5
927.0
2.45
2.7
179
64
13a
24.5
929.0
0.50
2.0
207
59
13b
26.0
945.0
0.50
2.0
184
59
14 (3 -cell)
64.0
926.0
0.97
2.9
164
64
15
19.0
918.0
1.00
2.8
228
62
15a
19.0
937.5
0.70
2.8
238
60
21
8.0
915.6
0.20
0.4
199
58
22
23.0
928.0
0.48
1.9
196
59
23
21.0
931.0
0.24
0.5
274
42
31
55.0
903.0
6.00
12.0
143
66
32
15.6
911.0
3.90
6.2
156
67
32a
47.4
911.0
0.70
2.9
206
57
33
32.0
904.5
2.20
9.5
146
69
34
29.0
912.0
0.23
0.8
255
46
42
81.0
915.0
2.40
15.8
158
68
43
26.0
924.0
0.62
2.0
261
56
44
45.0
931.0
1.70
6.6
239
60
45
19.0
934.0
1 3.50
1.8
152
66
46
14.0
935.0
1 2.90
1 14.5
135
1 70
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