SITE DRAINAGE (CHAPEL VIEW RES.)
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February 22, 1984
To: Planning Commission
From: JohnStrojan, City Engineer
Subject: Site Drainage - Chapel View Residences Addition
A Conditional Use Permit for the proposed Chapel View congregate care residences
(Case No. 84-04) was considered by the Planning Commission on January 31, 1984.
Extensive discussion took place in regard to the storm water drainage from the
site since there has been a history of i-ntersection flooding problems in the vi-
cinity, particularly at 6th Avenue & Third Street North during heavy rains.
The City Engineer described the pipe system which has been .installedand extended
over the past 40 years of the growth of the City. It was pointed out that it
would not. be feasible for reasons of cost, etc. to reconstruct the. system from
Nine Mile Creek to the upper portions of the contributing drainage area. Therefore
measures have to be taken to minimize and lessen any past or potential problems.
The most recent example was the relaying and rerouti-ng of a portion of the line on
6th Avenue South to an outlet in a larger pipe at the intersection of 8th Avenue &
Third Street. This work was done in 1970, including the upgrading of inlets to
lessen surface clogging from leaves, debris, etc. which in many instances is a
greater problem than possible inadequate pipe size. Another ongoing problem re-
lated to storm sewer adequacy is the need for the City to continually check and
clean the pipe and inlets of the buildup of sand deposits that reduce the carrying
capacity of the underground storm sewer system. Since the City is aware of this
area and other similar locations in the City this is a continuing task of the Public
Works Department.
The Commission continued the matter of the Conditional Use Permit for further con-
sideration by the applicant and City Engineer of the on site drainage proposals.
Since the last meeting the firm of Wehrman Consultants Associated, Inc. was engaged
by the architect to review the proposed site drainage. The City concerns were con-
veyed to Wehrman together wi th an exp.l anation of. the Ci ty storm sewer system in
place. As a result a revised drainage plan was~proposed which not only takes in
the roof drains directly, but was relocated to the private street on the east side.
This permits street inlets to be installed to pick up some of the surface drainage
not only from the site but also from the runoff of the previously developed areas
to the north. Presently much of this surface flow does not reach an inlet until it
reaches Minnetonka Mills Road. If this inlet cannot handle this flow, the water
will continue to flow on the surface to the intersection at Third Street & 6th Avenue
which is the low point.
In my opinion, the applicant has done everything within reason to collect and direct
the storm water from the site to minimize any adverse effects on other portions of
the drainage area. As was discussed at the last meeting, the City must continue to
observe and evaluate any future conditions and to take measures to remove or relieve
any such conditions. The applicant will be present at the Zoning and Planning meet-
ing to explain the revised site drainage plans.
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February 22, 1984
Site Drainage - Chapel View Residences Addition
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The drainage is without question going into Nine Mile Creek. However, the line
drawn between the two drainage districts is Mitinetonka Mills Road. The two
districts resolve problems such as this by having the legal drainage district
(Minnehaha Creek) review the proposal but use the criteria that the actual drain-
age area (Nine Mile Creek) would use.
Respectfully submitted,
t1Vv-l.~
John J. StroJan
City Engineer