CR 91-176 Prelim Report - Sewer Improvements RamsgateAy
August 15, 1991 ' Council Report: 91 -176
ACCEPT PRELIMINARY REPORT AND
ORDER SANITARY SEWER IMPROVEMENTS
RAMSGATE APARTMENTS
Proposed Action.
Staff recommends adoption of the following motion: Move that Council
adopt Resolution 91 -42. Resolution Accebtina Preliminary Report and
Ordering Sanitary Sewer Improvements at Ramsgate Apartments.
This action will continue a sanitary sewer improvement project at the
Ramsgate'Apartment site. Plans and specifications will be developed
for Council approval.
overview.
Development plans for a parcel east of the Ramsgate Apartments,
bounded by Hiawatha Avenue on the east and Cambridge Street on the
north, precipitated a closer examination of sanitary sewer main
capacity in Hiawatha Avenue. Preliminary findings showed residential
sewer backups and an undersized main in Hiawatha. Council at its
March 5 meeting authorized a feasibility study to evaluate alternative.
solutions to the problem. At its April 2 meeting Council was
presented the preliminary engineer's report. The most feasible
alternative called for rerouting of sewer main that required a utility
easement from the owners of the Ramsgate Apartment complex. Council
action was to hold for further information concerning easement
acquisition at the Ramsgate Apartments.
Primary Issues to Consider.
o Should the Council accept.the feasibility report?
o What are the engineer's conclusions and recommendations?
o Cost implications of easement acquisition and finding?
o Timetable.
Supporting Information.
o Letter from RCM 3/5/91
o Feasibility report 3/22/91
o Resolution 91 -42
James Gessele
Engineering Superintendent
Page 2
CR91 -176
Analysis.
o should the Council accept the feasibility report?
Staff finds the report to be complete with most options
explored and recommends its acceptance.
o What are the engineer's conclusions and recommenda-
tions?
The engineer concludes that the existing sanitary sewer in
Hiawatha Avenue inadequate in capacity and that either
replacing the pipe or rerouting a portion of the existing
contributing flow would significantly reduce the risk of
backups into homes in the neighborhood. A preferred
solution, to the problem would be to reroute flow from the
Ramsgate apartments to a new connection to the interceptor
sewer in Lake Street Northeast. Such rerouting would best
be accomplished by placing a new sewer main from the
apartment complex through its parking lot southward to Lake
Street Northeast.' Such a plan would require necessary
easements from the apartment owners and necessitate some
restoration costs. Assuming there would be no easement
acquisition costs, construction costs are estimated at
$47,060.
A.second alternative examined the rebuilding of the Hiawatha
Avenue system from Blake Road upstream to the drop manhole
where connection with the Ramsgate Apartments is made. This
would require replacement of 1455 feet of sewer pipe as well
as replacement of 1500 feet of Hiawatha Avenue street
surface. This alternative disrupts sewer service to
residents significantly 'and would cut access to homes for
some time. A street rated in fairly good condition and not
slated 'for reconstruction in the foreseeable future would
need to be restored. This alternative is estimated to cost
$106,100.
A third alternative not addressed in the report would also
reroute flow from the Ramsgate apartments to a new
connection in Lake Street Northeast. Rerouting would be
accomplished through the rear areas of westerly residential
lots fronting on Hiawatha Avenue. Although no cost estimate
is available for this option, the mere fact that soil and
ground water conditions would make- trenching difficult and
that a fifty foot wide swath of residential trees would be
cut through the neighborhood render this option impossible.
Here, too, easements across rear lot areas from residents on
Hiawatha Avenue would be necessary.
Page 3
CR91 -176
o Cost implications of easement acquisition and sources
of finding?
Given the staff's and engineer's recommendation that the
City pursue the first alternative, construction costs could
rise significantly if the Ramsgate Apartment owners refuse
to grant the City a utility easement. A comparison of two
scenarios is listed below.
Scenario 1
1. Ramsgate Apartment owners are cooperative and
assumption is utility easement is granted at no cost to
City.
2. Construction could begin this fall.
3. Risk of sewer backups in homes on Hiawatha Avenue would
be greatly reduced by this fall.
4. There would be minimal disruption of service and cost
of maintaining service to all residents in the
neighborhood.
5. Cost of the project estimated at $47,060.
Scenario 2
1. Ramsgate Apartment owners refuse to grant utility
easement across their property. The City is forced to
use condemnation proceedings.
2. Construction could not begin until spring 1992. A
quick taking of property for easement purposes requires
ninety days and this would delay the project well into
the winter months.
3. Risk of sewer backups in homes on Hiawatha Avenue would
be reduced by the spring of 1992.
4. There would be minimal disruption of service and cost
of maintaining service to all residents in the
neighborhood.
5. Cost of the project estimated as follows:
Costs of condemnation (legal and appraisal $ 30,000`.00
Easement acquisition 40,000.00
Construction costs 47,060.00
Total $117,060.00
Page 4
CR91 -176
Because condemnation proceedings would add significantly to
the cost of alternative one, it is in the City's interest to
acquire the utility easement at no cost. Staff recommends
that Council order plans and specifications for a project
that reroutes the sewer main through the Ramsgate Apartment
site contingent upon acquisition of a needed utility
easement at no cost to the City. With this action the
Council will have at minimum made a good faith effort to get
construction under way and will have addressed in part
liability issues regarding residential sewer backups.
Should staff encounter difficulties in easement acquisition
then a choice must be made in the near future between
alternative one clouded by condemnation proceedings or
alternative two that calls for the destruction/reconstruc-
tion of Hiawatha Avenue.
Funding for the project would come from sanitary sewer
utility funds.
o 1 Timetable
Under the most favorable conditions where no roadblocks lie
before easement acquisition, the following timetable is
envisioned:
August 20 Council orders plans and
specifications
September 3 Council approves plans and
orders bids
September 11 and 18 Bid ad in Sailor
September 13 and 20 Bid ad in Construction
Bulletin
September 23 Bid opening
October 1 Council awards contract
October 7 Construction begins
November 1 End construction
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. &CM
rieke
rroll
idler
wociates, inc.
en sneers
architects
land surveyors
equal opportunity
employer
March 5, 1991
Mr. Jim Gesselc, Engineering Supervisor
City of Hopkins
1010 First St. S.
Hopkins, MN 55343
RE: Ramsgate Townhouses
Letter #2
Storm Water Management, Sanitary Sewer
RCM Project No. 14000.08
Dear Mr. Gessele:
Z—
G
We have gathered more information since we sent our first letter, dated
February 25, 1991. We have met with: Ivan Nohner (Highland Villa
Builders), Duane Temple (Temple Associates), Nancy Anderson (City
Planning Department), and you.
We have also reviewed the sanitary sewer capacity along Hiawatha Avenue in
addition to storm water concerns.
Storm Water Management
We do not believe that reduced low area and pond volume as proposed is
acceptable since downstream residents would experience slightly increased
water levels. We recommend that the developer should increase the proposed
pond as described in our first letter.
The development, since its land area is very small compared to the drainage
area of Minnehaha Creek, will only have a small effect on the creek
elevation. 'During a 100 -year flood event, the development should . not
increase the creek elevation by more than one inch.
One house along Hiawatha Avenue appears to be lower than the 100-year
flood elevation. Another house reportedly is affected by the 100-year flood
in the creek.
Sanitar Sewer
We also reviewed concerns about sanitary sewer backups along Hiawatha
Avenue. The sewer accepts wastewater from Ramsgate Apartments, Creek
Point Apartments, Hiawatha Court Apartments, 13 houses, and Lift Station
#3. It discharges into a lift station owned by the Metropolitan Waste Control
Commission (MWCC). The proposed townhouses would also contribute
wastewater to this sanitary sewer.
The City Water and Sewer Utility Master Plan, prepared by RCM, noted a
problem area" on this sewer downstream of the area of concern. However, no
sanitary sewer backup complaints were on file with the City from this area.
Water use estimations show that flow to the sewer during a maximum day
demand may exceed the capacity of the sewer by about 30 percent.
Infiltration,, inflows, lift station #3 operation, and MWCC lift station
10901 red circle drive
box 130
minnetonka, minnesota 55343
612-935-6901
Mr. Jim Gessele
March 5, 1991
Page 2
operation may cause further sanitary sewer backups. Based on these
calculations, the existing sanitary sewer, with existing development, is
undersized. Any increased flow from new development would increase the
probability for sewer backups. The propose_ d Ramsgate Townhouses would
increase flows by about 3 percent.
Feasibility Study - Sanitary Sewer
Several alternatives could be implemented to control sanitary sewer backups
along Hiawatha Avenue. We propose the following feasibility study scope of
services to evaluate the alternatives.
The first part of the study will collect data necessary for the evaluations.
Basement elevations will be measured, and water level records in the MWCC
lift station will be obtained and reviewed. We would like the City to conduct
a survey of each home along the Avenue. RCM will discuss topics of this
survey with City staff.
Alternative sanitary sewer modifications will be evaluated, considering cost,
land availability, and effectiveness. We will summarize our findings in a
report to the City, and recommend an alternative that appears most feasible
for construction.
We will invoice the City for the feasibility study at our normal hourly rates
for the personnel working on the project up to a maximum of $4,500.
Summary
Under existing conditions, some of the homes along Hiawatha Avenue are
subject to water damage due to backups from the sanitary sewer or due to
flooding in Minnehaha Creek. Any development along Hiawatha Avenue
could increase the probability of water damage from both sources. We
recommend that a feasibility study be conducted to identify sanitary sewer
capacity solutions prior to additional development, and that new development
in the area include recommended storm water management measures to
minimize downstream surface flooding.
Please call us with any questions
Sincerely,
RIEKE CARROLL MULLER ASSOCIATE C.
Ilk
Dale Folen, P.E. Peter J. Carlson, P.E.
Project Engineer Project Manager
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FEASIBILITY REPORT
SANITARY SEWER SERVICE
s FOR
RAMSGATE TOWNHOUSES
HOPKINS, MINNESOTA
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RCM PROJECT NO. 10112.03
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March 22, 1991
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Mr. Jim Gessele
City of Hopkins
1010 1 st Street South
Hopkins, MN 55343
RE: Feasibility Report for Providing
Sanitary Sewer Service to
Ramsgate Townhouses
Hopkins, Minnesota
RCM Pro ject No. 10112.03
rieke
carroll
Dear Jim:
muller
associates, inc.
engineers
This report presents our findings, recommendations and a preliminary cost
for
architects
estimate providing sanitary sewer service for the proposed Ramsgate
land surveyors
Townhouses.
equal opportunity
employer
If you should have any questions regarding this report or require any further
data, please call me at any time.
Sincerely,
s
Peter J. Carlson, P.E.
RIEKE CARROLL MULLER ASSOCIATES, INC.
'
PJC /jj
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10901 red circle drive
box 130
minnetonka, minnesota 55343
612- 935 -6901
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RCM 10112.03
INTRODUCTION
This feasibility report has been prepared and is submitted to the City of Hopkins in
accordance with our proposal of March 5, 1991. By this proposal we were to provide an
analysis of the sanitary sewer system in Hiawatha Avenue, and make recommendations for
modifications to the existing system to allow service to the proposed Ramsgate Townhouses.
A proposal has been brought forth for the construction of 12 townhomes on a parcel of Iand
lying in the southwest quadrant of the intersection of Hiawatha Avenue and Cambridge
Street. Currently, the .average day sanitary sewer flows in the sanitary sewer that would
serve this site are approximately 88°x6 of the capacity of the system and the introduction of
additional flows from the -12 townhouses would raise the percentage to 90 %. Of a greater
concern, however, are the peak hour flows. Current peak hour flows are approximately 2.3
times the capacity of the existing system. With the additional 12 units, this factor would"
approach 2.4 times.
While there do not appear to be any significant problems in the system during times of
normal operation, this does appear to change at times of significant rainfalls (in excess of I-
1/2 - 2 inches). There have been reports from owners of some of the lower properties in the
area, that during periods of appreciable rainfall serious backups have occurred in the
sanitary sewer system which have resulted in basement damage to several of these low
residences. Due to the concerns of these residents, the City has chosen to review the inplace
system. The results of the review are presented in this report.
Page. I
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RCM 10 112.03
DESIGN
Improvement in the level of service of the sanitary sewer system in Hiawatha Avenue can
be accomplished with several solutions. Upon review it was determined that two (2)
potential solutions would be pursued as being the best alternatives. The first solution would
involve removing all of the current sanitary sewer flow from the, Ramsgate Apartments
from the Hiawatha Avenue system. This would require 200 lineal feet of existing 8 -inch
sanitary sewer be relaid, an existing manhole be rebuilt and would require the installation
of 460 lineal feet of new 8 -inch sanitary plus two additional manholes (see Figure 2). The
new segment of 8 -inch sanitary sewer would connect to the existing 33 -inch interceptor
sewer located in front of the Ramsgate Apartments in Lake Street N.E. With the
installation of this system, 88 gpm on an average day basis and 353 gpm on a. peak hour
basis would be eliminated from the Hiawatha Avenue system. These flows amount to 35%
of the flow on an average day basis and 55% of the flow on a peak hour basis. With the
elimination of these flows from the Hiawatha Avenue system, the flow rates in the last two
segments of the system in Hiawatha Avenue, which are the flattest and most critical, would
reach a level compatible with the capacity of the system.
Existing 8 -inch VCP Sanitary Sewer at 0.30%
Capacity existing:
Existing flow; average day basis:
Post development flow average day basis:
Existing flow; peak hour basis
Post development flow; peak hour basis
276 gpm
244 gpm
248 gpm
638 gpm
654 gpm
Should the Ramsgate Apartments be eliminated from the system, flow rates would be as
follows:
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Capacity existing:
Existing flow; average day basis:
Post development flow; average day basis:
Existing flow; peak hour basis
Post development flow; peak hour basis
276 gpm
156 gpm
164 gpm
285 gpm
301 gpm
Page 2
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RCM 10112.03
With the elimination of the Ramsgate Apartment flows from the Hiawatha Avenue system,
it can be seen that the opportunit for further incidents of backups would be greatly
reduced.
The second alternate would require the rebuilding of the Hiawatha Avenue system from its
beginning at Blake Road upstream to the drop manhole where the connection from the
Ramsgate Apartments is made, (see Figure 3). This would require the replacement of 1455
lineal feet of 8-inch clay sewer pipe with 850 feet of 8-inch PVC and 605 feet of 10-inch
PVC sewer pipe as well as the replacement of approximately 1500 lineal feet of Hiawatha
Avenue pavement.
Capacity Analysis
Existing 605 LF 8" VCP @ 0.30% Capacity 276 gpm
Proposed 605 LF 10" PVC @ 0.30% Capacity 700 gpm
Post Development Average Day Flow 248 gpm
Post Development Peak Hour Flow 654 gpm
Existing 850 LF 8" VCP @ 0.60% Capacity 390 gpm
Proposed 850 LF 8" PVC @ 0.60% Capacity 546 gpm
Post Development Average Day Flow 209 gpm
Post Development Peak Hour Flow 498 RDm
By replacing the existing 8-inch clay sewer pipe with 8- and 10-inch PVC, the flow
characteristics will be greatly enhanced and the opportunity for backups in the sanitary
sewer system will be minimized.
Page 3
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RCM 10 112.03
CONCLUSIONS AND RECOMMENDATIONS
1. The existing sanitary sewer, in particular the downstream 605 LF
prior to its
connection at Blake Road, appears inadequate to handle both current and post-
development sewage flows.
2. Increased capacity either replacing existing y y p g g piping with new more efficient
piping or by rerouting a portion of the existing flow should significantly reduce the
risk of backups into the lower lying homes in the vicinity.
3. Disruption of service and cost of maintaining service to all residents would be
{ minimal with the rerouting of the flow from Ramsgate Apartments to a new
connection to the 33 -inch interceptor sewer in Lake Street Northeast.
4. Total cost for replacement of sanitary sewer in Hiawatha Avenue and replacing the
street pavement, appears to be prohibitive in comparison to the cost of rerouting
flow from Ramsgate Apartments.
Page 4
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RCM 10112.03
COST ESTIMATE
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This cost estimate is based upon a review and capacity analysis of the
Hiawatha Avenue
sewer system and our recommended method
of relieving pressure on the inplace system. By
rerouting the flows from the Ramsgate Apartments to the 33 -inch interceptor sewer located
in Lake Street Northeast, it is anticipated that both the construction costs
and the amount
of - disruption will be significantly less.
Utility easement costs are not included in the cost
estimates below.
Q uantit y
price
Rerouting Solution
8" SDR 35 PVC, Sewer Pipe
850 LF
18.00
Unit Unit
10" SDR 35 PVC Sewer Pipe
Item
Q uantit y Price
Total
1. 8" SDR 35 PVC Sewer Pipe
660 LF 18.00
$11,880.00
2. 4' Dia. Standard Manhole
3 EA 1,100.00
3,300.00
3. 8" Outside Drop
.7.1 LF 125.00
887.50
4. Connect to Existing 33" Interceptor
1 LS 1,000.00
2,000.00
5. Bituminous Pavement
840 SY 8.00
6,720.00
6. Class 5 Aggregate Base for Pavement 280 TON 10.00
2,800.00
7. Replace Existing Curb
160 LF 7.00
1,120.00
8. Restoration (Sodding)
1650 SY 2.25
3,712.50
9. Dewatering
1 LS 2,000.00
2,000.00
10. Foundation Material
100 Ton 10.00
1.000.00
Subtotal
$35,420.00
Contingency
Contingency
3.140.00
Subtotal
$38,560.00
Engineering and Administrative
500.00
TOTAL
$47,060.00
Replacement
Solution
Unit
Unit
Item
Q uantit y
price
1.
8" SDR 35 PVC, Sewer Pipe
850 LF
18.00
2.
10" SDR 35 PVC Sewer Pipe
605 LF
22.00
3.-
4' Dia. Standard Manholes
4 EA
1,100.00
4.
Connect to Existing Manhole
2 EA
300.00
5.
Service Wyes
17 EA
40.00
6.
( Service Pipe
425 LF
10.00
7.
Bituminous Pavement
3850 SY
5.00
8.
Class 5 Aggregate Base for Pavement 1270 TON
10.00
9.
Restoration (Sodding)
2000 SY
2.25
Subtotal
Contingency
Subtotal
Engineering and Administrative
TOTAL
Page 5
Total
$ l 5,300.00
13,310.00
4,400.00
600.00
680.00
4,250.00
19,250.00
12,700.00
4.500.00
$74,990.00
11,110.00
$86,100.00
20. 000.00
$106,100.00
I 4
CITY OF HOPKINS
Hennepin County, Minnesota
RESOLUTION NO: 91 -42
RESOLUTION ACCEPTING PRELIMINARY REPORT AND
ORDERING SANITARY SEWER IMPROVEMENTS AT RAMSGATE APARTMENTS
WHEREAS, a` preliminary report has been prepared with respect to
the improvement of sanitary sewer main at the Ramsgate
Apartment site, and
WHEREAS, the engineer has advised this Council that the
aforesaid improvement is feasible and should best be
made as proposed at an estimated cost of $47,060.00 by
rerouting sewer through the Ramsgate Apartment site,
and
WHEREAS, the City Council deems it necessary and expedient that
the City of Hopkins construct the aforesaid improvement
in accordance with the report;
NOW THEREFORE BE IT RESOLVED BY THE CITY COUNCIL OF HOPKINS,
MINNESOTA:
1. Such preliminary report is hereby approved
and ordered placed on file in the office of
the city clerk.
2. Rieke Carroll Muller Associates, Inc. is
hereby designated as the engineer for this
improvement and shall prepare plans and
specifications for the making of such
improvement contingent upon a utility easement
granted to the City by Ramsgate Apartments.
3. The engineering superintendent is directed to
immediately begin easement acquisition negotiations
with the owners of the Ramsgate Apartments.
Adopted this day of August, 1991.
ATTEST:
Nelson W. Berg, Mayor
James A. Genellie, City Clerk