HomeMy WebLinkAboutStephens Subdivison Lot A B C Floodplain Study
To: Lot B, Stephens Subdivision Town of Vail Legal File
From: Warren Campbell, Chief of Planning
Date: March 18, 2013
Subject: Lot B Buildable Site Area
This memorandum is to serve as the document establishing the buildable site area for Lot B,
Stephens Subdivision. In 2006, the Town of Vail commissioned a site specific floodplain
study of Lots A, B-1, B-2, C, and D of the Stephens Subdivision by Hydrosphere. The results
of that study confirmed that Lots A, B-1, B-2, C, and D were within the Gore Creek floodplain.
Furthermore, the study provided a solution to lessen the impact of the floodplain on these lots.
The construction of the structure on Lot B-2 (B08-0340) implemented a portion of the
recommended floodplain mitigation by raising a portion of the site out of the floodplain. The
recommendation of the Hydrosphere plan involved Lots A, B-1, B-2, C, and D, however, not
all property owners have implemented the plan at the time of this memorandum.
This resulted in the anticipated buildable site area for Lot B being less than anticipated by the
Hydrosphere study as improvements to the adjacent lots have yet to be implemented.
It is anticipated that as Lots A, B-1, C, and D redevelop, the remainder of the Hydrosphere
study is likely to be implemented. In an effort to achieve a definitive buildable site area for Lot
B, staff has decided to use a buildable site area for Lot B of 15,390 square feet as identified in
the April 24, 2006 Planning and Environmental Commission Memorandum (PEC06-0001 and
PC06-0027). This memorandum identifies in the zoning analysis that the implementation of
the Hydrosphere study resulted in Lot B achieving a buildable site area of 15,390 square feet.
This buildable site area will be used in determining the allowable Gross Residential Floor Area
(GRFA) for Lot B.
At the time this memorandum was written the allowable GRFA for the site is 5,540 square
feet. Should the zoning designation or method for the calculation of GRFA change for the
property the allowable GRFA may be altered.
__________________________________________________________________________________________
Department of Public Works & Transportation
MEMO
To: Planning and Environmental Commission
From: Tom Kassmel, Floodplain Coordinator
Re: Stephens Park Subdivision Floodplain Modification Application
Date: April 24th, 2006
Summary & Recommendation
The Town of Vail has received application for modification to the 100 Year Floodplain in the Stephens Park
Subdivision Vicinity, more specifically lots A, B-1, B-2, C and the unplatted western portion of Stephens Park
(denoted as D on Hydrosphere’s Floodplain Study map). The modifications include placing fill in the shaded
areas as shown on the attached map to a level above the Base Flood Elevation (BFE), placing approximately 0’
to 1’ of fill within the floodplain. Per Title 12 -21-10-E the Town has required an engineered analysis of the
proposed modifications to establish that the modifications will not adversely affect adjacent properties, or
increase the quantity o r velocity of flood waters. Based on this analysis we have concluded that the proposed
modifications meet the above criteria and recommend the floodplain modification request be approved with the
following conditions:
1. Prior to any modification, excavation or placement of fill within the 100 yr floodplain;
a. All improvements/modifications shall comply with the study and letter completed by
Hydrosphere Resource Consultants dated 2/14/06 and 3/29/06 respectively.
b. DRB and Building Department approval shall be obtained.
c. A CLOMR-F (Conditional Letter of Map Revision based on Fill) or CLOMR
(Conditional Letter of Map Revision) shall be filed and approved by FEMA.
2. Upon completion of the improvements/modifications within the 100 year floodplain;
a. All conditions of the FEMA approved CLOMR-F or CLOMR shall be satisfied.
b. A LOMR-F (Letter of Map Revision based on Fill) or LOMR (Letter of Map Revision
based on Fill) shall be filed and approved by FEMA
c. An As-built survey with the modified 100 year FEMA approved floodplain line placed on
it shall be filed with the Town of Vail.
3. All new building structures placed upon any fill improvement shall meet the FEMA criteria to be
considered not in the 100 Year floodplain and also be a minimum of one (1.0) foot above the
FEMA app roved BFE, thus providing 1.0 foot of freeboard for all new building structures.
The study report and letter stamped by a Colorado professional engineer are attached for you review.
Background
The above mentioned properties are currently located within the 100 year floodplain as designated by FEMA in
both the 1982 and the 2005 floodplain studies. However since 1983 the Town of Vail has recognized these
parcels, or at least the buildable portions of these parcels, as being out of the floodplain due to the completion of
a man-made berm/levee and concrete block wall. This has created a conflict between development practice
within this area and the Town code. In short the Town regulates the 100 Year Floodplain based upon the
approved FEMA 100 Year Floodplain designation, per title 12-21-11 of the Town code. Since the berm/levee
and wall improvements were never submitted to FEMA they were neither reviewed nor recognized by FEMA,
therefore they should not have been recognized or approved by the Town of Vail. However since they were
approved by the Town, development has occurred within this floodplain area. In the most recent FEMA
floodplain study (c. 2005) it is evident that FEMA does not recognize the berm/levee and wall improvements
since they do not meet the current FEMA floodplain mitigation criteria. Therefore the Town of Vail should no
longer accept this area as not in the floodplain.
The problem then is having approved developed areas within the 100 year floodplain. The solution is to remove
this area from the floodplain in accordance with both Town of Vail and FEMA requirements. Since this area is
designated by FEMA as a Flood “fringe” area, fill improvements are allowed by filing a CLOMR or CLOMR-F
and then following up after the improvements wit h a LOMR and LOMR-F. The process is relatively straight
forward. The Town of Vail requirements are more restrictive in that an engineered analysis and PEC approval
are required in order to make any improvements/modifications within the floodplain.
At this point in time it is appropriate to satisfy the Town of Vail requirements by gaining PEC approval for
modifications to the floodplain. PEC approval should be conditioned with FEMA’s approval via the LOMR
process and in addition those conditions stated above. The ultimate goal is to have those parcels located within
the Stephens Subdivision to have the opportunity to remove themselves from the 100 year floodplain according
to their own timetable.
The attached study report and letter provide additional background and technical information for your review.
1002 Walnut St. Suite 200
Boulder CO, 80302
303-443-7839
Hydrosphere Resource Consultants
General PlanKinnickinick Floodplain Study
FEMA 100-Year Floodplain (Proposed) - Based on FEMA Computed
Water Surface Elevations and FEMA Base Mapping
HRC 100-Year Floodplain - Based on FEMA Computed Water
Surface Elevations and Detailed HRC Base Mapping
Approximate Even Foot 100-Year Interpolated Water Surface Elevation
Based on FEMA Computed Water Surface Elevations Computed at
Cross-Sections 115, 116, and 116.5 for Gore Creek32'
Floodway (Proposed)
For Shading and Hatching Description, Refer to Associated Report