HomeMy WebLinkAboutSection 3: Hydrologic Analysis
3.0 Section 3 - Hydrologic Analysis
3.1 Hydrologic Analysis
The St. Joseph area that is included in the hydrologic modeling study area
includes the City of St. Joseph and the planned annexation area,
approximately 10.5 square miles (6700 acres). Figure 13 shows the Study
Area and the watersheds delineated for the hydrologic study.
Existing and developed conditions watersheds and routing were evaluated
using HydroCAD® 7.0. HydroCAD utilizes hydrologic techniques developed
by the NRCS (the unit hydrograph) to predict runoff from a given rainfall
event. Separate models were created for the existing and developed land use
conditions to evaluate peak runoff rates, Ponds were added to the 4eveloped
conditions model as treatment systems for the runoff. The models were
created from the best available information as described below,
Figures 14-18 each show sections of the larger watershed in more detail.
Developed conditions treatment ponds and storm water routing is also shown
on these figures. Tables 10-12 show the characteristics and outflow results
data for the: Watersheds-Existing Conditions; Watersheds-Developed
Conditions; and Ponds-Developed Conditions, respectively. Analysis of the
watersheds and outflow data is kept to a minimum and Tables 10-12 are used
to present the data,
3.2 Watersheds
Watershed boundaries are based on topographical information fromtwo main
sources:
. Two-foot contour maps of the area from a City mapping project where
aerial photographs were used to create contour data.
. Ten-foot contour United States Geological Survey Quadrangle maps.
Watershed boundaries were determined based on USGS quadrangle
information where that was the only topographic information available.
3.3 Soils Information
The soil types present in each watershed is an important hydrologic factor for
determining runoff rates and volume, Information about the soil types in the
watersheds is shown on Figure 6 and presented in Section 2 of this report,
3,4 Land Uses and Curve Numbers
The NRCS Curve Number (CN) is used to estimate runoff volume from a
watershed. The CN is determined as a function of land use, soil type, and
hydrologic soils group. Land uses for the model were determined from aerial
photography of the area supplemented with City maps and development
plans. Antecedent moisture conditions (AMe) also affect runoff volumes.
Curve numbers were assigned to the different land uses based on NRCS
recommendations.
An AMC of 2, simulating average moisture conditions, was assumed for all
modeling runs.
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3.5 Time of Concentrations
Time of concentration (Tc) is the time it takes runoff to travel from the
hydraulically most remote point on the watershed to the watershed outlet. Tc
is used to determine the magnitude of the runoff peak. The time of
concentrations for the modeling was determined using the NRCS sheet flow
and shallow concentrated flow methods.
3.6 Existing Conditions Modeling Results
A summary of hydrologic properties and outflow rates for each watershed is
provided in Table 10. More detailed infonnation is presented in Appendix F,
Existing Conditions Hydrologic Modeling Results.
3.6,1 Watersheds
The existing conditions watersheds were delineated as large areas with an
average size of 93 acres for the 65 watersheds. The median size is 55 acres.
Existing land use outside of the current St. Joseph City limits includes
agricultural uses, wooded, meadow and wetland areas, and isolated single-
family homes. The aerial photo background used in Figures 13-18
graphically presents the existing land use data, The CNs reported in Table 10
show the result of averaging the land use CNs over each watershed.
There is no existing stonn drainage system for the areas outside of the
developed City, and much of the runoff from each watershed currently flows
to existing low areas or wetlands. Because of this, each watershed was
analyzed in existing conditions as a separate entity, without routing water
from one watershed to the next.
3.6.2 Drainage Results
The watershed outflow rates for the 10- and lOa-year events are shown in
Table 10. These rates represent existing conditions outflow rates for each
watershed if all the water from that area were to discharge at one location.
Stonn water would not actually discharge at one location from a watershed in
undeveloped condition, but the outflow rate is used for comparison to
developed conditions outflow rate results,
3.6,3 Storm Drain System
The existing stonn sewer system for St. Joseph is shown in Figures 14-18
(red lines and labels). The stonn sewer system flows to two major outlets,
Mill Creek pond and the Watab River on the north side, and ponds and
wetlands on the south side of town, Other stonn sewer outlets go to isolated,
landlocked low areas,
Currently, stonn drainage is provided through a combination of stonn sewer
and some open ditches in the City of St. Joseph. Much of St. Joseph is served
with stonn sewer or ponds. The City also requires stonn sewer to be installed
with the reconstruction of streets. This policy may not always be feasible or
practical, so alternate design standards may be used when appropriate, such
as drainage ditches.
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3.7 Developed Conditions Modeling Results
A summary of hydrologic properties and outflow rates for each watershed is
provided in Table 10, More detailed information is presented in Appendix G,
Developed Conditions Hydrologic Modeling Results.
3.7.1 Watersheds
The watershed boundaries and wetlands were kept the same in existing and
developed conditions as much as possible, in order to facilitate comparisons
between the two conditions. Several of the areas were subdivided into
smaller areas in order to size a storm water runoff pond that was not too
large. Some of the watersheds within the existing sewered area were left out
because there are no plans to change them or add ponds in the future.
The developed conditions watersheds were delineated as large areas with an
average size of 52 acres for the 111 watersheds. The median size is 37 acres.
When development plans are finalized in some of these areas, the boundaries
will likely be altered with the detailed grading plans. Wetlands will need to
be delineated and proposals will likely be made to relocate or fill some of
them.
In many cases portions of these watersheds will develop within property
boundaries rather than watershed boundaries. The property and watershed
boundaries are often not the same. Because of this the developed condition
watershed boundaries will change from what is presented here as
development progresses. The regional pond concepts will still be valid, but
the pond sizes may change with revised watershed boundaries.
Watershed peak outflow rates for the 10- and 100-year storm events
increased in many watersheds for developed conditions compared to existing
(Table 10 and 11). This is caused by increased runoff rrom the developed
condition impervious areas, changed vegetative cover, and general grading
which will remove existing low spots. St. Joseph requires that the developed
conditions outflow rate for any given area be less than or equal to the
existing conditions outflow rate. To accomplish this storm water treatment
ponds are used to detain peak flow rates and discharge storm water more
slowly.
3.7,2
Land Use
Developed conditions land use was assumed to be residential development
for most of the watersheds. The City's Future Land use Plan (Figure 11) was
utilized to determine the proposed density. The developed conditions
watersheds were modeled with a combination of paved roads and 1/4 to 1/2
acre housing developments. Some small areas of wooded, meadow, and
wetland were left in place to maintain some ofthe existing land-use diversity,
3.7.3
Wetlands
The wetlands in existing and developed conditions were not changed to
facilitate comparison between the land-use changes and addition of the
storm-water ponds. Wetlands were not modeled as a part of this modeling
project. Wetland outflows and peak elevations may decrease in developed
conditions because the added storm-water ponds provide temporary runoff
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storage functions that the wetlands provide in existing conditions.. Wetland
outflows and peak elevations may increase because of the increased amount
of flow :trom the developed watersheds. The actual volume of water will
increase in developed conditions, but the peak outflow rates will be
attenuated through addition of the ponds. The wetlands will need to have
positive outflow maintained in order to prevent flooding from the increased
runoff volume,
3,7.4 Storm Water Ponds
Storm-water ponds were added to each watershed near the outflow location
to provide water quality treatment prior to the water being released :trom the
watershed. The ponds were designed with the following criteria:
· Sized large enough to hold the 100-year storm without overtopping
the upper contour of the pond,
· 10- and 100-year outflow rates are less in the developed .condition
compared to the watershed outflow rate in existing condition.
· NPDES Water Quality storm event (2.5 inch) criteria met.
· Stagged outflow device with an 18 or 24 inch RCP outflow culvert,
an 8 inch low flow inlet and a high flow 48 inch wier.
· Emergency overflow wier 1 foot below the top of the pond,
· 6:1 side slopes with a 10:1 bench at the outflow elevation (normal
water level, NWL).
Using these criteria, the required pond sizes are shown on Figures 14-18 and
listed in Table 12. The pond area shown in Table 12 is at the top of the pond.
Four feet of vertical storage is provided above the NWL as a conservative
pond sizing criteria.
The locations of the ponds will change once detailed grading plans are
available. In several cases, property boundaries or fmal grading will show
that several smaller ponds may better suit the developer's plans than single,
large ponds. However, these proposed pond sizes indicate what will be
required to meet the City's treatment and outflow rate goals.
The ponds are usually located in natural low lands or inlets to lakes. It should
be noted that the City would need to further investigate the proposed regional
pond locations with respect to jurisdictional wetlands and regulatory
restrictions that may affect the construction of these facilities. Even though
this report evaluates the proposed construction of regional ponds, other storm
water treatment best management practices (BMPs) (such as infiltration
BMP's) will be addressed in the feasibility study stage,
The Minnesota Urban Small Sites BMP Manual (Metropolitan Council,
2001) outlines a three-step process to select a BMP or combination ofBMPs
for sites less than one acre. This process looks at storm water treatment
suitability, physical feasibility factors, and community and environmental
factors.
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3.7.5 Summary Discharge Data
HydroCAD® modeling was completed for the 96 proposed regional ponds.
At this stage the pond locations and configurations are conceptual, and
therefore the modeling consisted of sizing the ponds to meet the above
criteria and treating the watershed runoff, The ponds are assumed to be
kidney shaped, with a ten-foot shelf below the NWL (pond outlet elevation),
Pond side slopes are set at 6:1 above the NWL, 10:1 at the NWL, and 3:1 to
the bottom, The pond depths are designed at 3 feet below the NWL.
Appendix H includes pond design standards for the City.
The 2-, 10-, and 100-year, 24-hüur storm events were run, using antecedent
moisture conditions (AMe) II. AMC II means that there is an average
amount of soil moisture present before the storm goes through an area. The
results ofthese models can be seen in Appendix G.
The 100-year storm event was used to calculate a peak elevation for each
pond.
3.8 Proposed Regional Water Quality
The storm water ponds are designed to meet MPCA pond design
recommendations, which will result in 90 percent total suspended solids
(TSS) removal and total phosphorus (TP) removal where the phosphorus is
associated with small sized particles. These results are achieved through a
combination of the pond storage volume and the controlled discharge rate.
MPCA requires that the discharge rate for a water-quality (WQ) storm event
should be less than 5.66 cfs/acre to achieve settlement of TSS in the pond
after the water-quality storm event.
A WQ storm event is defined by MPCA as the volume equivalent to one-half
inch of rain over the new impervious area in a watershed. This is the
definition MPCA uses when requiring a permanent storm water pond size for
new construction.
Several jurisdictions in the State require that storm water ponds be sized for
the 2.5-inch rain event, which is approximately equal to the 2-year storm
event. This will result in a larger pond volume in most cases than the MPCA
defmed event.
The most conservative pond designs generally come from the combination of
requirement that the developed conditions 100-year storm discharge rate be
less than or equal to the existing conditions discharge rates and that the WQ
storm event be released at less than 5,66 cfs/acre. In most cases these
requirements will ensure that the pond is large enough to easily hold the 2.5-
inch event volume and that the WQ event discharge rate will allow TSS
settlement.
3.8.1
Lakes
The MPCA and MNDNR maintain lake information databases on many lakes
in Minnesota, The data is available on the WEB at
www.pca,state.mn.us/water/lakequality and www.dm.state.mn.us/lakefind.
Summary water quality data is available on the MNDNR site for some of the
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Storm Water Management Plan
St. Joseph, Minnesota
lakes in the St. Joseph area. Table 4 provides a list of the lakes in the St.
Joseph area.
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TABLE 10: WATERSHEDS - EXISTING CONDITIONS
Watershed Size (ac) Average CN Peak Outflow
010 (c1s) 0100 (cfs)
1 to 4 Outside of St. JoseJh Annexation Area
5 97.8 82 183.1 315.9
6 40.8 75 113.3 210.7
7 229.8 72 102.9 208.5
8 48.2 74 39.5 77.2
9A 33.9 84 35.7 60.4
9B 28.6 76 26.3 49.8
9C 9.3 76 19.8 36.9
10A 4.9 75 10.6 20.0
10B 19.0 61 12.7 34.1
10C 29.0 64 20.0 48.9
11A 27.4 76 50.3 94.0
11B 45.6 74 76.5 147.5
12 23.8 78 48.0 87.0
13A 25.8 65 14.1 33.6
13B 23.9 74 44.0 84.6
13C 65.6 72 50.1 101.7
14A 29.9 70 30.0 63.0
14B 13.6 70 18.9 39.2
15 66.1 74 105.5 204.0
16A 61.7 65 20.9 49.5
16B 61.0 72 55.1 111.6
16C 59.6 70 49.8 105.0
17 101.6 78 97.5 178.9
18 35.8 70 31.1 65.4
19 37.0 76 40.5 76.5
20 91.9 69 73.2 157.8
21 19.2 73 12.0 23.9
22 31.3 62 17.1 44.9
23 94.7 59 17.4 49.5
24A 30.8 55 4.5 15.5
24B 34.9 74 38.4 75.0
24C 15.1 75 9.4 18.0
30A 25.0 70 19.4 41.0
30B 119.0 65 37.5 88.8
30C 37.5 67 33.9 76.0
300 32.5 86 73.2 120.1
31 16.0 83 67.9 113.1
32 112.3 84 534.8 877.4
33 42.0 76 40.2 76.0
34A 40.6 67 18.0 40.9
34B 80.9 77 111.1 206.1
34C 71.2 74 35.6 70.0
340 34.8 79 52.9 95.3
35 295.3 76 152.2 289.7
36 80.1 75 68.4 131.7
37 98.8 75 53.4 102.8
38 39.8 77 79.1 145.5
39 225.9 75 777.7 1429.6
40 217.6 74 60.7 118.4
41 214.5 72 153.6 312.1
42A 402.9 64 76.4 185.2
42B_1 50.5 75 25.2 48.8
42B_2 180.6 76 44.6 84.8
42C_1 165.0 78 142.6 262.1
42C_2 190.0 81 96.4 169.7
420 112.0 81 80.1 141.0
44 526.2 59 47.0 124.7
45 171.7 69 22.2 46,8
46 231.3 70 101.9 215.4
47 150.0 83 167.7 287.1
51 139.3 73 76.4 152.1
52 116.6 62 27.3 71.1
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TABLE 11: WATERSHEDS - DEVELOPED CONDITIONS
Watershed Size (ac) Average CN Peak Outflow
010 (cIs) 0100 (cIs)
1 to 4 Outside of St. JoseJh Annexation Area
5A 24.6 63 11.5 29.1
58 72.7 71 82.2 168.8
6 40.8 73 53.3 105.4
7 Existing City - Storm Sewered area
8 48.2 64 26.7 65.6
9A 33.9 75 33.0 63.4
98 28.6 74 30.8 60.1
9C 9.3 81 13.7 24.0
10A 4,9 69 7.1 15.0
108 19.0 60 12.2 34.0
10C 29.0 57 10.4 33.7
11A 27.4 62 15.2 39.7
118 45.6 58 17.2 53.2
12 23.8 66 23.0 52.6
13A 25.8 67 23.8 53.3
138 23.9 69 18.9 40.7
13C 65.6 63 46.2 116.2
14A 29.9 70 30.0 63.0
148 13.6 70 18.9 39.2
15 66.1 74 105.5 204.0
16A 61.7 71 82.2 168.2
168 61.0 70 72.9 152.1
16C 59.6 72 63.2 127.7
17A 73.4 71 71.1 146.7
178 28.2 60 12.7 35.9
18 35.8 82 56.1 97.0
19 37.0 76 34.7 65.8
20A 26.7 76 52.7 98.3
208 20.1 80 37.6 66.5
20C 45.1 82 73.5 127.0
21 19.2 92 55.3 84.6
22 31.3 83 59.9 102.0
23A 55.7 82 80.5 139.2
238 39.0 84 80.6 135.3
24A 30.8 85 66.8 111.0
248 34.9 88 55.9 89.7
24C 15.1 82 22.8 39.5
30A 25.0 77 29.8 55.5
3081 30.6 92 68.8 105.4
3082 18.2 82 31.8 54.9
3083 70.2 91 169.5 262.4
30C 37.5 90 135.5 210.9
300 Existing City - Storm Sewered area
31 Existing City - Storm Sewered area
32 Existing City - Storm Sewered area
33A 29.8 88 54.1 86.8
338 12.2 88 30.9 49.4
34A 40.6 88 105.7 168.9
3481 40.6 88 93.3 149.3
3482 40.3 89 160.8 252.3
34C Existing City - Storm Sewered area
340 34.8 88 62.2 99.8
35A 32.5 87 100.6 162.0
358 66.7 87 164.1 265.4
35C 27.8 85 60.7 100.8
350 45.5 85 79.8 132.7
35E 67.6 87 99.3 161.5
35F 55.3 87 85.6 139.2
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TABLE 11: WATERSHEDS - DEVELOPED CONDITIONS
Watershed
36A
36B
37A
37B
37C
38
39A
39B
39C
390
39E
39F
39G
40
41
42A
42B_1
42B_2
42C_1
42C_2
420
44A
44B
44C
440
44E
44F
44G
44H
441
44J
45A
45B
45C
450
45E
46A
46B
46C
460
46E
46F
46G
47
51A
51B
51C
52A
52B
Storm Water Management Plan
51. Joseph, Minnesota
Size (ac)
49.0
31.1
26.7
35.3
40.7
39.8
30;3
49.3
23.3
43.1
31.3
30.5
19.0
217.6
214.5
402.9
50.5
180.6
163.5
190.0
112.0
28.4
67.0
30.3
19.3
83.9
41.9
34.5
77.8
74.2
68.5
32.8
37.0
45.9
38.1
17.4
40.9
34.7
34.6
21.3
48.1
16.1
35.8
150.0
27.7
44.8
66.7
53.4
63.2
Average CN
88
88
88
88
88
88
88
88
88
88
88
88
88
74
72
64
92
76
70
71
72
83
67
69
82
62
65
90
65
71
85
93
92
92
92
94
92
92
91
93
92
93
93
72
92
86
71
74
70
Peak Outflow
Q10 (cts) Q100 (cfs)
65.3 105.0
53.5 85.9
42.7 68.5
56.8 91.3
60.0 96.3
77.6 124.4
45.3 72.9
68.6 110.3
32.5 52.3
61.1 98.1
75.2 120.3
73.3 117.3
41.8 67.0
60.7 118.4
153.6 312.1
76.4 185.2
48.9 75.4
88.1 167.6
113.7 240.6
71.3 147.7
104.4 211.3
56.6 96.3
46.7 105.7
27.6 59.3
32.1 55.5
26.8 70.1
15.8 37.7
46.8 73.6
41.7 99.9
54.7 113.2
156.7 259.6
62.7 95.3
72.2 110.8
71.6 109.9
77.7 119.3
26.1 39.4
85.3 130.9
89.3 136.7
72.1 111.8
37.0 56.3
100.5 154.2
31.1 47.2
75.4 114.5
150.8 305.2
46.1 70.7
62.7 103.3
50.6 104.8
100.5 193.1
48.3 101.9
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TABLE 12: PONDS - DEVELOPED CONDITIONS
Peak Outflow Normal Volume (A F)
Wetland/ Surface Water Peak Water Inflow for
Pond Area Size O2 010 0100 Level Level- 100yr Normal Top of a 1 OOyr
(ac) (cfs) (cfs) (cfs) (ft) (ft) Water Level Pond Storm
(AF)
5A 1,0 0.4 1,2 10.0 1065 1067,3 1,0 4.0 4,2
58 2.9 1,2 4,8 27.0 1061 1064,3 5.6 15.7 16,6
6A 1,7 1,2 4,2 20,9 1067 1070.4 2,7 8,3 9.9
8 1.3 0,8 2.6 19.4 1073 1076.4 1.7 5.9 8,5
9A 1.5 1.3 5.4 20,7 1080 1083.4 2,1 6,8 8.8
9B 1.2 1,5 7.5 30.6 1073 1076,7 1.5 5,3 10,1
9C 0.6 1,3 2.9 12.0 1079 1081,7 0.3 1,9 2.9
10B 0,6 0,3 1.5 11,6 1061 1063,5 0,3 1.9 2,8
10C 0,6 0.3 1,7 12,5 1057 1059,9 0,3 1,9 3,7
11A 0,8 0,5 1,9 12.5 1083 1085,9 0,6 2,8 4.5
118 1.0 0.4 1,9 13,5 1078 1081.1 1.1 4.0 6.2
12 0,8 0.7 2.0 14.6 1071 1074,2 0.6 2,8 4.6
13A 0,8 0,3 1,7 12,5 1096 1098,9 0.6 2.8 5.1
13B 1.0 0,8 2.0 12.3 1093 1095,8 1.0 4,0 5.1
13C 2,0 0.8 2,1 15,1 1075 1098.2 3,3 10.0 11.1
14 1.3 1.8 5,9 13,2 1081 1084.1 1.8 6.0 9.6
16A 2,6 1.2 3.7 18,7 1081 1084.3 4.8 13.7 14,1
16B 2,6 1,1 2,9 15.9 1075 1078,2 4.8 13.7 13,5
16C 2,6 1,5 3,8 18,9 1073 1076.4 4.8 13.7 14,1
17A 2,9 1,2 5.0 23,3 1067 1070,5 5,6 15,7 16,8
178 0.6 0,5 2,0 16.3 1069 1072.2 0.3 1.9 4,2
18 2.3 1.4 4.8 16.7 1073 1076.3 4,0 11.8 11,3
19 1,7 1,3 5.2 19.4 1077 1080.4 2,7 8,3 9,9
20A 1.2 1.3 4,9 22.4 1112 1115,5 1.5 5,3 7,1
20B 1.2 1,3 3.1 13,9 1079 1082,1 1,5 5.3 6.0
20C 2,9 1.5 5.1 17.5 1077 1080,3 5.6 15,7 14,3
21 1.5 1,9 10,8 22,2 1085 1088,5 2,1 6,8 7,8
22 1,5 0,6 2,1 15,7 1065 1068,2 2.1 6.8 10,2
23A 2,9 1.7 10,9 33.1 1073 1076,8 5,6 15,6 17,7
238 2,6 1,6 6,1 19.2 1073 1076.4 4.8 13,7 13,0
24A 2,0 1,6 7,5 21.4 1079 1082.4 3.3 10.0 10.6
24B 2,6 1.7 7.8 18,6 1079 1082,3 4,9 13,8 12,9
24C 0.8 1,6 8,2 19.1 1079 1082.4 0.6 2.8 4,8
30A 1.2 1.3 4,6 17.4 1093 1096.3 1.5 5,3 6,9
3081 2,6 1.8 8.6 18.2 1091 1094,3 4.8 13,7 12.4
3083 6,0 1.8 9,1 20,6 1077 1080.4 13,6 35.5 27,9
30C 2,9 1,8 8,9 21.8 1087 1090,5 5,6 15,7 14,5
33A 2,0 1.8 10,3 23,6 1083 1086,5 3,3 10,0 11.0
338 0,8 1.8 10.3 21.0 1085 1088.4 0.6 2.8 4,5
34A 2,9 1,7 9.2 23.4 1071 1074,5 5,6 15,7 15,0
34B1 2,9 1.7 9.3 23,2 1065 1068.5 5.6 15.7 15,0
34B2 2,9 1,8 10.0 25,6 1063 1066,6 5,6 15.7 15,2
340 2,6 1.7 7.8 19,0 1065 1068.4 4.8 13,7 12,9
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TABLE 12: PONDS - DEVELOPED CONDITIONS
Peak Outflow Normal Volume (A F)
Surface - Peak Water Inflow for
Wetland/ Water
Pond Area Size O2 010 0100 Level Level- 100yr Normal Top of a 1 OOyr
(ac) (cfs) (cfs) (cfs) (ft) (ft) Water Level Pond Storm
(AF)
35A 2.3 1.9 7.5 20,9 1093 1096.4 4.0 11,8 11,7
358 4,3 1,6 6,8 24,7 1065 1068,2 9,2 24.7 20,7
35C 1.7 1,6 8,8 23.7 1065 1068,5 2.7 8,3 9.5
350 2,9 1.7 9.0 24.4 1063 1066,5 5.6 15.7 15,6
35E 2.9 2.0 12,0 39.2 1061 1064,9 5.6 15,7 18,7
35F 4.3 1.6 6.3 17,1 1061 1064.3 9.2 24,7 19,9
36A 2,9 2,0 11.7 34.8 1065 1068,8 5,6 15,7 18.1
368 2.3 1,7 7.9 18.7 1065 1068.3 4,0 11.8 11.5
37A 1,7 1.8 10.7 23.5 1067 1068,5 2.7 8.3 9.9
378 2,6 1,7 8,2 19.4 1065 1068.4 4,8 13.6 13.0
37C 2,9 1,7 9,5 21,5 1065 1068.4 5.6 15,7 15,0
38 2,9 1,9 8,5 20.7 1063 1066.4 5.6 15.7 14,7
39A 2,0 1,8 10,6 23.4 1063 1066,5 3.3 10,0 11,2
398 2.9 2.0 11.8 35,9 1065 1068.9 5.6 15,7 18.2
39C 1,5 1,8 10.5 21.6 1063 1066.5 2.1 6,8 8.6
390 2.9 1.8 10.8 25.4 1063 1066,6 5.6 15,7 15,9
39E 2.3 1,7 7.9 15.6 1063 1066.4 4.0 11,8 11.5
39F 2.3 1.7 7.0 18.6 1065 1068,3 4.0 11.8 11.3
39G 1,3 1.7 8,7 19.4 1064 1 067.4 1,7 5,9 7,0
41 College of St. 8enedicts and Convent Properties
428_1 5,3 4.4 8.4 21.0 1086 1088,5 11,9 31,2 20,5
428_2 7.9 1,7 14,2 46,3 1075 1078,8 18.7 48,0 48.3
42C_1 5,3 1,5 11,2 63.0 1065 1068,6 11,9 31.2 36.1
42C_2 6,9 1.5 10,0 37.4 1055 1058,7 16.5 43.4 43,4
420 5.3 1.3 4.6 23,5 1055 1058.1 11.9 31.2 26.4
44A 1.7 1.5 6,7 20.7 1063 1066.4 2.7 8.3 9,3
448 2,3 1.4 6.8 33,7 1061 1064,8 4.0 11,8 19.6
44C 1.0 1,0 3.8 21,2 1059 1062.4 1.0 4,0 6.5
440 1,0 1,6 9.2 23,1 1061 1064,5 1,0 4,0 6,1
44E 2.3 0,8 2.5 18,1 1053 1056,3 4.0 11,8 13.7
44F 1,0 1,0 4,8 21.3 1053 1056.4 1,0 4.0 7.7
44G 2,6 1,8 9,9 20,0 1057 1060.4 4,8 13.7 13.4
44H 2.3 1,0 3,8 23,0 1051 1054,5 4,0 11,8 14.3
441 2.9 1,3 5,1 23,5 1047 1050,5 5.6 15.7 16,9
44J 5,3 1.6 5.2 15.3 1051 1054,2 11.9 31.2 22.5
45A 2,6 2.0 11,0 23,7 1065 1068.5 4,8 13,6 13,6
45B 2.9 1,9 10.9 23.5 1061 1064,5 5.6 15,7 15.0
45C 2.9 2,2 12.4 39,2 1057 1060,9 5,6 15,7 18.6
45D 2.9 1,9 11,1 26.1 1058 1061.6 5,6 15.7 15,5
45E 1,2 2,1 11,2 20,3 1057 1060.4 1.5 5.3 7.4
46A 2.9 2.0 11,6 32,0 1063 1068.7 5,6 15,7 16,6
46B 2,9 1.8 9.2 19,8 1057 1 060.4 5.6 15.7 14.1
46C 2.6 1,9 11.0 25,2 1055 1058.6 4,8 13,6 13,7
Storm Water Managment Plan A-ST JOE 0315
St. Joseph, Minnesota Page 30
2003 Storm Water Management Plan
ST, JOSEPH, MN
Ä-ST JOE 0315
8/11/2004
TABLE 12: PONDS - DEVELOPED CONDITIONS
Peak Outflow Normal Volume (A F)
Wetland/ Surface Water Peak Water Inflow for
Pond Area Size O2 010 0100 Level Level- 1 OOyr Normal Top of a 1 OOyr
(ac) (cis) (cis) (cis) (ft) (ft) Water Level Pond Storm
(AF)
460 1.7 1,9 9.9 17.5 1057 1060.3 2.7 8.3 8.8
46E 4.3 1,8 7,6 17,2 1055 1058.3 9.2 24.7 19,5
46F 1.2 1.9 10,5 18.4 1055 1058,3 1.5 5.3 6,7
46G 2,9 1.9 10.9 23,2 1051 1054,5 5.6 15,7 14,9
47 6,0 1,5 8.8 52.1 1055 1058.4 13.6 35.5 35.4
51 A 2,0 1.9 11,2 24.5 1101 1104,5 3.3 10.0 11,3
51B 2,9 1,7 9,9 24.3 1101 1104,5 5.6 15,7 15.8
51C 2,6 1.2 4,9 23.0 1101 1104.5 4,8 13.7 15.2
52A 2.3 1.3 5.5 25.2 1101 1104.6 4.0 11,8 13.4
52B 2,3 1.2 4.9 24.0 1107 1110,5 4,0 11.8 13.9
x:\S\stjoe\031500\reports\spreadsheets\watersheds_wetlands-ponds.xls
Storm Water Managment Plan
St. Joseph, Minnesota
A-ST JOE 0315
Page 31