Sky Blue Estates Stormwater Management Information Follow Up Copyright 2014
City of Dubuque Consent Items # 6.
ITEM TITLE: Sky Blue Estates Stormwater Management
SUMMARY: City Manager transmitting information relating to the
stormwater management issues that arose during
construction of the first phase of the Sky Blue Estates
Subdivision and outlining steps taken to address the issues
and prevent repeating them as a result of the development
of Sky Blue Estates #2.
SUGGESTED DISPOSITION: Suggested Disposition: Receive and File
ATTACHMENTS:
Description Type
Sky Blue Estates Stormwater Management-MVM Memo City Manager Memo
Staff Memo Staff Memo
Vicinity Map Supporting Documentation
Aerial Map Sky Blue Supporting Documentation
Grading Plan Sky Blue No. 1 and No. 2 Supporting Documentation
THE CITY OF Dubuque
DUB E i"
Masterpiece on the Mississippi 2007.2012.2013
TO: The Honorable Mayor and City Council Members
FROM: Michael C. Van Milligen, City Manager
SUBJECT: Sky Blue Estates Stormwater Management Issues
DATE: December 13, 2016
City Engineer Gus Psihoyos is transmitting information relating to the stormwater
management issues that arose during construction of the first phase of the Sky Blue
Estates Subdivision and outlining steps taken to address the issues and prevent
repeating them as a result of the development of Sky Blue Estates #2.
1 �) k�4 dlL.A^l
Mic ael C. Van Milligen
MCVM:jh
Attachment
cc: Crenna Brumwell, City Attorney
Cindy Steinhauser, Assistant City Manager
Teri Goodmann, Assistant City Manager
Gus Psihoyos, City Engineer
THE CITY OF - Dubuque
DUB .L MI-AmedcaChy
Masterpiece on the Mississippi 2007.2012•2013
TO: Michael C. Van Milligen, City Manager
FROM: Gus Psihoyos, City Engineer �,qQ
SUBJECT: Sky Blue Estates, Stormwater Management Issues
DATE: December 13, 2016
INTRODUCTION
The purpose of this memo is to provide information relating to the stormwater management
issues that arose during construction of the first phase of the Sky Blue Estates Subdivision
and to outline steps taken to address the issues and prevent repeating them as a result of
the development of Sky Blue Estates #2.
BACKGROUND
In July of 2012, the City Council passed Resolution 186-12 approving the Final Plat of Sky
Blue Estates. Per the Resolution, the "(Developer) must construct and maintain erosion
control devices in Sky Blue Estates which control erosion and prevent sediment from
leaving the site."
In November of 2016, the City Council passed Resolution 405-16 approving the Final Plat
of Sky Blue Estates #2. Per the Resolution, the "(Developer) must construct and maintain
erosion control devices in Sky Blue Estates which control erosion and prevent sediment
from leaving the site."
DISCUSSION
Two stormwater issues arose during construction of the first phase of Sky Blue Estates
due to the means and methods chosen by the developer to transform the property into
buildable, residential lots: increased, unmitigated runoff and sediment leaving the site to
the detriment of downstream properties along Shiras Avenue. Both issues are corrected
through the development of Sky Blue Estates #2.
The developer was required to develop a Storm Water Pollution Prevention Plan (SWPPP)
which must address all potential pollutants associated with the development of the
property. They created a SWPPP calling for "sediment and erosion practices, interceptor
dikes and swales, and temporary sediment basins." Because a SWPPP must evolve as
conditions change, as grading and construction progresses towards completion, the
SWPPP acknowledged that it was to be used "as an initial guide and (the
Developer/Contractor) shall modify, add, and/or move controls as needed to prevent
sediment from leaving the site." On multiple occasions, the erosion and sediment controls
proved inadequate to prevent sediment from leaving the site prompting the City to issue a
violation letter and a municipal citation demanding remedy. The erosion and sediment
control issue was exacerbated by the fact that the Developer did not limit the clearing of
trees and ground cover to just the first phase of the subdivision. They cleared areas
associated with Sky Blue Estates #2 as well. The denuding property was more susceptible
to erosion, requiring more controls than the Developer originally planned. These additional
controls have been installed and tested so that construction of Sky Blue Estates #2 can
proceed with a more robust erosion and sediment controls already in place.
When the Developer expanded the grading limits beyond the first phase of the subdivision,
increased runoff resulted. Even though the graded area remained pervious, the absence of
trees and ground cover reduced the interception of rain in the tree canopy, eliminated the
evapotranspiration of rain back into the atmosphere, and reduced the infiltration into the
soil. Though modest in nature, the increased runoff flowed unmitigated from the site
creating issues for downstream property owners. The development Final Plat for Sky Blue
Estates #2 outlines the construction of two detention basins. The entire site is to be graded
so that all stormwater from the subdivision will be directed to detention basins. Stormwater
will drain from the basins through a new storm sewer to be constructed between the basins
and the downstream storm sewer system on Shiras Avenue. This was made possible by
the developer acquiring property on Shiras Avenue solely for the purpose of connecting
the two systems. Moreover, the detention basins have been sized based on the capacity of
the downstream storm sewer system. Following the completion of Sky Blue Estates #2, no
stormwater will flow uncontrolled from the subdivision.
The Engineering Department will continue to work with the Developer during construction
to ensure that the erosion and sediment control plan continues to provide adequate
measures, prevent sediment from leaving the site.
ACTION TO BE TAKEN
No action is requested. This memo is to provide information only.
Attach.
Prepared by Deron Muehring
cc: Laura Carstens, Planning Services Manager
Deron Muehring, Civil Engineer
Dean Mattoon, Engineering Technician
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