HomeMy WebLinkAboutWEBERG PUD - PRELIMINARY - 76-88F - CORRESPONDENCE - STORMWATER-RELATED DOCUMENTSUtii• Services
Stormwater
City of Fort Collins HAND DELIVERED
April 14, 1989
Mr. Lloyd McLaughlin
Mr. Brian Cole
RBD, Inc.
2900 South College Avenue
Fort Collins, Colorado 80525
RE: Weberg PUD
Dear Lloyd and Brian:
Since there are several outstanding issues and questions on the Weberg PUD
site, I wanted to document them in a letter.
Last week (April 4, 1989) I met with Kevin Mill (Mill Brothers Nursery) and
Bob Wilkinson (Natural Resources Department) to take an up -close look at the
pond system located downstream of the Weberg site. We looked at the three
ponds, and their connecting channels, ending up at the Cameron Park
development.
Since you are proposing to drain a portion of the Weberg site into this
drainage system I feel it is important for you to be aware of some of the
concerns that came up based upon this site visit.
1. Water Quality
It looks like you are already making headway on addressing the water quality
issues and coming to an agreement with the offsite landowners. It did
come up at the site meeting that Mill Brothers does not own the entire
pond that is situated directly behind their building. They own only a
small portion of it and have rights to pump water out of it. The
remainder of the pond is located on property owned by a general
partnership. One of the members of this partnership is Paul Heffron. I
have spoken with Paul about the site, and he was not aware that the City
has required the Developer of the Weberg site to negotiate an agreement
with the offsite property owners. Any agreement made must include all of
the owners, not just Mill Brothers.
2. On -site Detention and Staged Release Rate
Even though the site is located in the Fossil Creek Basin, in which
there is not a basin benefit for on -site detention, the particular
circumstances of this site (ie: the downstream conditions) necessitate
detention. At the initial preliminary review I stated that a staged
release rate would be allowed. The question has come up, what storms
must be matched? For instance, should the 10 year and 100 year storms
be matched? I have had discussions on this with Brian and said that I
would discuss this issue with Bob Smith. Both Bob and I agree that the
downstream conditions must dictate the allowable release rate.
235 Mathews - P.O. Box 580 - Fort Collins, CO 80522-0580 - (303) 221-6389
In your Preliminary Drainage Report there is a description of the outfall of
the Weberg site all the way down to Fossil Creek. However, there is not yet
an assessment of whether or not the runoff from the developed Weberg site
will have an adverse impact on the downstream ponds. The site visit
revealed that the embankment of the uppermost pond shows signs of erosion.
The only outlets from the two ponds just downstream of the site are
"overflow ditches" which carry water down to the next pond. The channel
downstream of the middle pond and just upstream from the Cameron Park pond
shows severe erosion. What will be the impact of developed flows on these
existing facilities? An assessment must be made of these restrictions
before a detention release rate can be decided. For instance, a smaller
release rate may be required due to the restriction of the overflow ditch
capacity. If a larger release rate is desired, perhaps the overflow ditch
can be enlarged and stabilized. The increase in volume may necessitate
erosion control protection farther downstream. In other words, it is not
appropriate to arbitrarily choose a detention release rate. The downstream
impacts must be addressed, and then an appropriate release rate chosen.
I'd like to point out that the Stormwater Utility does have the authority to
impose stricter criteria than the master plan shows if there are downstream
impacts which must be mitigated. For your information, I have attached the
pertinent sections of our criteria.
I have also reviewed the revised Preliminary Drainage Report and Grading
Plan. For Preliminary approval it is sufficient, however, prior to Final
approval the offsite impacts must be resolved and the agreements with the
offsite landowners obtained. Please refer to the revised drainage report
and grading plan for additional comments.
If you have any questions or comments, or would like to meet to discuss
these issues, please call me at 221-6589.
Sincerely,
Susan Duba Hayes
Civil Engineer II
cc: Sherry Albertson -Clark, Planner
Mike Herzig, Development Review Coordinator
Frank Vaught, Vaught -Frye Architects