DFHADprototype071409.. - Urban Drainage and Flood Control District

DFHAD Prototype
720 S. Colorado Boulevard, Suite 410 S
Denver, Colorado 80246
phone (303) 757-3655
fax (303) 300-1635
PROGRESS MEETING FOR
HOFFMAN DRAINAGEWAY PLANNING & FHAD STUDY
MEETING MINUTES
Date: July 11, 2007
Location: Urban Drainage and Flood Control District Conference Room
Distributions: none
Attendees:
Name Organization Email
Ben Urbonas UDFCD burbonas@udfcd.org
Ken MacKenzie UDFCD kam@udfcd.org
Pete Brezall City of Thornton pete.brezall@cityofthornton.net
Chris Crowley City of Thornton chris.crowley@cityofthornton.net
Marques Granderson City of Thornton marques.granderson@cityofthornton.net
Matthew Pacheco LCC Ditch Co. matthew.pacheco@cityofthornton.net
Besharah Najjar Adams County bnajjar@co.adams.co.us
Jessica Stevens Adams County Jestevens@co.adams.co.us
Teresa Patterson Moser & Associates patterson@moser-eng.com
David Delagarza Moser & Associates delagarza@moser-eng.com
I. Purpose
The purpose of the meeting was to discuss the Project Sponsors’ review comments on
the Phase A – Development of Alternate Plans report.
II.
Phase A Report Review Comments
Ken and Besharah supplied Moser with copies of the report with their review comments;
Jessica provided a CD that contained a scan of her comments; and Pete distributed a
hard copy of an email that had review comments from City of Thornton and also sent an
email with additional City of Thornton comments.
Lower Clear Creek Canal (LCCC) – The figure illustrating the conceptual configuration
for separating the Hoffman Channel from the LCCC ditch flows was discussed. Matt
stated that the ditch company supported the general idea of the configuration as
illustrated in the report, but that they would like to see a waste gate and emergency
overflow provided. Moser will add a note to the figure stating that a waste gate and an
emergency overflow shall be provided. Moser will also revise the figure to show a
rectangular ditch section instead of a trapezoidal section.
88 th Avenue & Cross Culvert – We discussed the flooding at issues at the intersection of
Hoffman Way and 88 th Avenue. Chris Crowley pointed out that the crown of 88 th Avenue
is much higher than the gutters and asked if lowering in the crown would help alleviate
the flooding in that area. The cause of the flooding is water breaking out of the Hoffman
III.
IV.
Way street section to the houses which are lower than the curb line. Lowering the crown
of 88 th has little effect on the flooding upstream.
We also discussed that the culvert under 88 th Avenue is a 60” CMP in poor condition and
that 88 th Avenue is overtopped frequently, including the 10-year event.
It was noted that there are multiple detention facilities in the upper end of the watershed.
It was discussed whether accounting for them in the hydrology would affect the peak
flows enough to show a benefit and whether their storage could be guaranteed for
perpetuity. It is the District’s policy that planning studies only recognize facilities under
the maintenance and control of the local government to ensure its existence. Moser will
experiment with flows near 88 th to determine the threshold at which flooding occurs for
the one new house within the floodplain boundary.
McElwain Blvd. – The alternatives illustrate discharging the proposed storm sewer east
of Devonshire. Adams County requested that for Alternatives 2-4, the outfall flows north
to the Hoffman culvert under Devonshire, eliminating one culvert crossing.
86 th Avenue Concrete Channel option – Moser will add a discussion in the report that the
concrete-lined channel shall be designed in accordance with USDCM Major
Drainageway chapter. The report will also note that chain-link fence will be required
around the perimeter of the channel and shall be equipped with a complete underdrain
system and shall be constructed of reinforced steel.
Thornton Water Treatment Plant
The 2007 FHAD (draft currently being reviewed) shows the area north of 86 th Avenue
and east of the LCCC in a shallow flooding area. The Thornton Water Treatment Plant
(WTP) lies within this boundary. City of Thornton is concerned about the flood insurance
implications and asked that Moser take a more detailed look at that area. Thornton
supplied the as-builts for the WTP grading plan and a CD of additional survey shots in
the area. Moser will assess the capacity of the ditch west of the WTP to determine if it
has adequate capacity to divert the shallow flood flows around the plant. If additional
information is needed, Moser will contact Thornton. Moser will also supply an
addendum to Ken for this additional work.
Community Meeting
A community meeting has been scheduled for Thursday, July 19 th at the Thornton Civic
Center. Residents that could potentially be affected by the FHAD floodplain update were
invited to attend this public meeting. Moser will prepare exhibits showing the old and
new floodplain lines and the structures affected and an exhibit of the Recommended
Plan. Jessica is going to put together some information about obtaining flood insurance.
Hoffman Drainageway Planning & FHAD
Progress Meeting Minutes 07/11/07
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Hoffman Drainageway Planning & FHAD
Progress Meeting Minutes 07/11/07
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