CR 98-098 Consider Feasibility Report, Storm Drainage Problem Area 5 Auth Additional Engineering Service Fees-Area 5Proposed Action.
Overview.
Supporting Information.
S Y
June 11, 1998 Council Report 98 -098
Consider Feasibility Report, Storm Drainage Problem Area 5
Authorize Additional Engineering Services Fees — Area 5
Staff recommends adoption of the following motion: Move that Council authorize
additional engineering services fees to RCM Associates in an amount not to
exceed $2,500 for additional work on storm drainage problem area 5.
On November 5, 1997, City Council adopted by resolution an action plan to
address last summer's storm and sanitary sewer problems. Regarding problem
area 5, the action plan requires the city to confirm that the proposed 6 Avenue
storm sewer project will improve drainage in this alley. RCM has analyzed the
current drainage areas and overland flow as it relates to area 5, the alley
between 8 and 9 Avenue North and 2" and 3 Street North. They report that
the eh Avenue storm sewer project will not improve drainage in this alley. Staff
would now like to look for improvement alternatives. This will require a detailed
topographic survey of this area including elevations for yard and boulevard
areas, garages, houses, streets and alleys and additional time for analysis of this
data to identify feasible alternatives. If this request for additional engineering fee
is approved, RCM and staff will expand the scope of the feasibility report to
include alternatives, cost estimates and a recommended course of action. The
City cost to -date for Area 5 engineering services is $750.00
Staff and Mike Foertsch, RCM Associates, will present the feasibility report to
Council and answer questions.
• Feasibility Report — Area 5
Action Plan
Steven J. Stadler, Public Works Director
0
Feasibility Report
Storm Water Flooding Analysis
Area 5 - Alley Between 8th & 9 Avenue North
Hopkins, MN
RCM File No. 10441
10901 red circle drive • box 130 • minnetonka, mn 55343 • (612)935 -6901 • fax (612)935 -8814
June 1998
AREA -5: ALLEY BETWEEN 8TH AND 9TH AVENUES NORTH
ISSUES:
The alley between 8 and 9 Avenues North and 2nd and 3r Streets North, reportedly flooded on two
occasions during July of 1997 and once during May 1998. Drainage from this area was improved
slightly in 1992 with the 1st Street North storm sewer project. The intent of the 1992 improvements
was to maximum the available pipe capacity within the existing storm sewer system. That project was
not expected to solve the problem, but simply allow a slight improvement. A portion of the storm
water flow was diverted away from the Mainstreet and 7 Avenue area also. The 6th Avenue North
storm sewer improvements do not provide an increased level of protection.
ANALYSIS:
This area (Figure 2) is drained by a 24 -inch storm sewer pipe which drains southerly to the existing
storm sewer system in 2nd Street North. The low point in the alley is drained by two existing catch
basin inlets. The capacity of the two inlet catch basin grates is approximately 6.5 cfs. The capacity
of the existing 24 -inch storm sewer pipe (Figure 3) is estimated at 13 cfs. The "localized" drainage
area to this alley low point is approximately 3 acres (Figure 4). The estimated storm water flows
from this 3 acre area are about 2.1 cfs and 3.8 cfs during the 10 year and 100 year frequency storms,
respectively.
The difficulty in draining this alley comes from the condition that it is a major flow path in the
watershed that drains south and easterly to the low point at 6 Avenue and 1s Street North. Since
the middle of the alley is lower than the south end, some of the water flowing along the alley is
trapped. This causes the flooding condition.
Overland flow from approximately 25 acres (Figure 5) is tributary to this low point. During the
rainfall events which exceed the existing pipe capacities within the drainage district, the flow to this
alley area in the 100 year storm event is estimated at approximately 35 cfs from this 25 acre area. In
addition, there is testimony from residents who live in this area that flow from property located north
of Minnetonka Mills Road flows easterly along Minnetonka Mills Road and southerly along 8
Avenue North (Figure 5). A portion of the flow along 8 Avenue North splits and goes west on 3rd
1
Street North and a portion of it goes south along 8 Avenue North. The portion of the flow which
flows westerly along 3r Street North also enters the low point in the alley between 8 and 9th
Avenues at its intersection with 3rd Street North.
On May 15, 1998, residents in this area reported as much as 2- inches of rainfall within a 20 minute
period. During that rainfall event, the water ponded to a depth of approximately 1.7 feet. This
1.7 foot depth was verified by water lines on the existing structures adjacent to the low point in the
alley. The low point elevation of the overland flow point (Figure 5) from this location is at the
intersection of 2n Street North and the alley. This intersection elevation is approximately 1.8 feet
above the low point in the alley. As a result, in rainfall events which exceeds the inlet capacity of the
existing storm sewer system, the water ponds to a depth of approximately 1.8 feet before overflowing
southerly onto r Street North. The overland flow on 2 Street North is easterly to 7 Avenue
North and then southerly along 7 Avenue North..
2
FIG -2.DWG 6— '10 -98 PLOT 1 - -1 PN.10441.05
5TH ST N.
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AREA NO.4
SERVICE
MAINSTREET
1
AREA NO
REVISIONS
AREA NO.2
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11
AREA NO.3
C I T Y
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H O P K I N S
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Carroll
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associates, inc.
engineers architects land surveyors
It
A.
SERVICE ROAD
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FIGURE 2
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STUDY AREAS
HOPKINS, MINNESOTA
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DATE
JUNE 1998
Z
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SHEET NO
FILE NO.
10441.05
FIG -3.9WG 6 -10 -98 PLOT 1 -1 PN.10441.05
MAINSTREET
SERVICE RUAD
7
alli rieke
Carroll
muller
associates, inc.
engineers architects land surveyors
FIGURE -3
1
EXISTING STORM SEWER SYSTEM
HOPKINS, MINNESOTA
REVISIONS
DATE
JUNE 1998
SHEET NO.
FILE NO.
10441.05
FIGURE 4.DWG 6-11-98 PLOT 1-100 PN.10441 .05
924.6
CI" ri r k r e
coll
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associates, inc.
engineers architects • land surveyors
--
3rd STREET
923.8
X
FIGURE NO.4
NORTH
925,2
X
6 23 ca 'cn (23
X
932.6
934.6
SHEET NO.
926.
/
3 ACRE LOCAL DRAINAGE AREA
HOPKINS, MINNESOTA
NORTH 15"
922.4
SCALE: 1" = 100'
REVISIONS
DATE
JUNE 1998
X
FILE NO.
10441.05
FIG -5.DWG 6 -10 -98 PLOT 1 -1 PN.1044 i .G5
= Overland Flow
Clii rieke
carroll
muller
associates, inc.
7 • architects land surveyors
FIGURE 5
EXISTING TRIBUTARY
DRAINAGE AREAS
HOPKINS, MINNESOTA
REVISIONS
DATE
JUNE 1997
SHEET NO.
FILE NO.
10441.05
3. Alley Between 1 7th
&18th Avenues
Contact: Steve Stadler
Public Works Director
Phone 612 -939-1382
Fax 612-939-1381
Action plan designed to alleviate flooding problems
Input sought before City Council approval, Wednesday, Nov. 5
The city of Hopkins has developed a proposed action plan to address storm drainage or sanitary sewer
problems in eight areas of the community. The action plan includes projected completion time frames. The
Hopkins City Council at its meeting, Wednesday, Nov. 5, will consider the plan, and public input is invited.
Written input into the action plan may be sent to the Public Works Director or City Manager's Office.
Questions may be directed to Steve Stadler, Public Works Director, 939 -1382
Completion
Problem area Action Date
1. Shady Oak Pond A Dredge Pond and improve ponds edges 1999
B. Construct pond outlet as part of drainage
improvements associated with Shady Oak
Road reconstruction
2. Hilltop Park low area A Complete drainage improvement project
design
B. Complete drainage improvement area
A Consider altematives & design
improvements to alley drainage
B. Complete Construction
4. North of Maetzold Field A Investigate and design new storm water
structure to increase flow capacity from
13th Avenue inlets to Maetzold Field
B. Complete construction of improvements
2001
JANUARY 1998
OCTOBER 1998
JANUARY 1998
OCTOBER
1998
JANUARY 1998
OCTOBER 1998
•
sewemr10- 29.doc
4. North of Maetzold Field C. Complete capacity analysis of existing DECEMBER
(continued) sanitary sewer collection pipes serving this 1997
area
D. Complete repairs to collection pipes, if
there are capacity problems because of
defective parts
5. Alley between 8th & 9th
Avenues North
6. 6th Avenue North/3rd
Street North storm sewer
project
7. Hobby Acres
8. 2nd Street Northeast &
Monroe Avenue North
E. Complete sump pump inspections of homes
and businesses in this sanitary sewer area
and analyze results
F. Disconnect any improper sump pump
connections in this service area
A Confirmation that the proposed 6th Avenue FEBRUARY
storm sewer project will improve drainage 1998
in this alley
A Project design completion
B. Storm drainage improvement project
construction completion
A Capacity analysis of existing sanitary sewer
collection pipes serving this area
B. Complete repairs to any defective pipes
C. Complete sump pump inspections of
homes and businesses in this sanitary
sewer service area and analyze results
D. Disconnect any improper sump pump
connections that are found in this area
B. Complete construction of any necessary
improvements
DECEMBER
1998
MARCH 1998
NOVEMBER
1998
FEBRUARY
1998
NOVEMBER
1998
DECEMBER
1998
DECEMBER
1997
MARCH 1998
NOVEMBER
1998
A Complete analysis of drainage capacity for FEBRUARY
this area 1998
NOVEMBER
1999