HomeMy WebLinkAboutA006 - Letter to Mayor and Council dated December 17, 2002 from Bloomington Townhome Association December 17, 2002
4233 Eisenhower Court
Ames, Iowa-50010
Phone 515-233-2319
Mayor and City Council
City of Ames
City Hall
Ames, Iowa
Re: Blooming- ton Heights West Subdivision
The following comments and reguest is made on behalf of the Bloomington
Townhomes Association,Ames, Iowa.
The Bloomington Townhomes Association (BTA) is located to the east of the
subdivision development now in question. Having commented on the development
previously, we still have one remaining significant concern regarding the
development we wish to address to you.
Surface water runoff and erosion control downstream
A drainage channel serving the proposed development also traverses the northern
portion of the BTA's development site. We are concerned about this new
development causing flooding and uncontrolled erosion, due both to an increase in
the total volume of water and the rate at which it will be dumped into this surface
drainage channel. The channel is already too steep to maintain the gradient of the
streambed without serious further erosion, even without increases in the amount of
water and rate of flow being handled. This new subdivision development will
seriously increase both.
The proposed "on-site" impoundment of development's runoff drainage is apparently
designed to control the release rate of surface water, restricting it to a rate equal to a
current once in "two-year event." Nominally, this means the flow in the channel will
not exceed what would otherwise be expected to be an extreme event occurring only
once every two years. However, with the increased amount of runoff due to the
development, and the reduced time of concentration of the drainage on that
development site, we will now see much smaller storms turned into routine once in
"two-year" discharge events, an occurrence that will happen many times each year.
We will be threatened with extended drainage periods and substantial erosion as a
result, both occurring far more often and for longer periods at this "two-year' rate.
As a result, the frequency expectation of only once in two years will no longer protect
us. Instead, this will greatly accelerate the erosion of the streambed and threaten
the BTA's buildings and landscaping. Without further retention capacity, partially to
support lesser discharge and reduce the frequency of this extreme discharge to the
true standard of once every two years by today's measurement, we will be without
adequate protection.
We were initially advised by City staff that plans for the Conservation Preserve area
north of our development, and the proposed rechanneling to carry the drainage to
the Preserve, would alleviate these concerns. However, the City's development of
plans for that work has been delayed and we are unable to verify such assurances.
So, we are unable to adequately assess this threat and any possible relief. City
representatives have agreed to provide an opportunity to review such drainage
plans, as those preliminary plans become available. They described expected
outcomes that can adequately respond to our concerns.
Staff has been most supportive of searching for reasonable solutions to this
problem. However, as we understand that the development in question is funding
"mitigation" measures, we ask for assurance that any necessary adjustments to the
drainage channel will be completed as a development mitigation, and done so at no
cost to BTA. This would primarily be accomplished by maintaining the actual
channel to the northern most possible side of the drainage easement being
established to serve the Preserve where the channel is adjacent to our residential
site.
Thank you for the opportunity to share our concerns and comment upon the
proposed development.
Submitted by:
Ian MacUilli� y
President '
Bloomington Townhomes Association
4233 Eisenhower Court
Ames Iowa