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HomeMy WebLinkAbout1.03 Floodplain AnalysisApril Long, PE Colorado Watermark, LLC 1215 County Road 112 Carbondale, CO 81623 970-901-6082 March 20, 2019 Glenn Hartman, CFM Community Development Department 108 8th Street, Suite 401 Glenwood Springs, CO 81601 970-945-8212 RE: Floodplain Analysis, 2101 County Road 245, New Castle, CO 81647 Dear Mr. Hartman, The Longacre Equine Campground is planned to be located off the banks of Elk Creek in unincorporated Garfield County, near the Town of New Castle. The project is located within a larger agriculture property and work is proposed within the 100 -year floodplain designated as Zone A. The facility will include tent camping sites, access roadways, and potentially a gazebo or pavilion for common use by guests. The area of disturbance and development is located outside of the 35 -foot water body setback but within the 100 -year floodplain. I have reviewed the site plans for the Longacre Equine Campground project (project), the effective FEMA Flood Insurance Rate Map of 1986 (Panel 0802051015 B), the Preliminary FIRM Panels 1105E and 1108E of 2011, and the standards set forth in the Garfield County Land Use and Development Code (Code) and provide the following comments on the noted sections of the Code as they pertain to development within a floodplain. 3-301 Floodplain Overlay Regulations A. Use Restrictions. Based on the information in Table 3-301, the development or use of overnight campgrounds, recreational and open space structures, and roads and trails are all permitted within the 100 -year floodplain. The development and use of overnight campgrounds are not permitted within the floodway. B. General Standards. The Longacre Equine Campground is a primitive campground and will not include any mechanical equipment or utilities, water supply systems, sanitary sewer systems, or on- site waste disposal systems. A non -permanent and portable toilet will be located near the campground but outside of the 100 -year floodplain, based on an estimated base flood elevation of 5670. The camp sites will be designated by railroad ties anchored to the surface and the covered pavilion will be anchored to posts set in concrete. These materials should be resistant to flood damage and these anchoring methods will be adequate to prevent the materials from flotation, collapse, or movement resulting from rising and moving floodwaters. C. Specific Standards. The project is not proposing any enclosed structures or manufactured homes and recreational vehicles will not be allowed. The project may include a gazebo or pavilion, but this structure will have no rigid walls, will not be enclosed, and will have low flood -damage potential, and therefore, is typically classified as an "accessory structure," as defined on FEMA's website, which is not required to be elevated or floodproofed. D. Floodway. Because the proposed project is located within a Zone A designated floodplain, no floodway has been determined for the area. However, all proposed work for the project is located 4 vertical feet above and 50 horizontal feet beyond the ordinary high-water mark of Elk Creek. Additionally, substantial riparian vegetation exists between the proposed campground and Elk Creek which should reduce velocities of floodwater and the concern for floodway encroachment. E. Standards for Areas of Shallow Flooding. Areas for shallow flooding have not been designated on the reviewed flood maps. Slight grading is proposed within the floodplain to create a gravel access road and to flatten camp sites. Any cut from grading will be used as fill to raise camping platforms. Purpose of raising camping sites is to provide protection from small and more frequent storm events. These raised campsites will also allow adequate drainage paths that guide flood waters around and away from tent locations. The next downstream structure is approximately one-half mile away. These small alterations to the site will not adversely impact adjacent or downstream properties. F. Properties Removed from the floodplain by Fill. Property has not been removed from the Floodplain by issuance of a FEMA Letter of Map Revision. G. Alteration of a Watercourse. Project will not alter a watercourse. H. Standards for Critical Facilities. Project is not a Critical Facility. 4-109 Development in the 100 -Year Floodplain C. Review Criteria — respond with non -applicable or addressed. 1. Due to the temporary nature of camping, dangers to life and property should be limited. The campground will be staffed, and this staff person will notify campers to evacuate during the threat of flood. Campers will likely be very aware of and uncomfortable in intense or extended storm events that are likely to cause flooding and will seek higher ground and shelter. Property owner will post sign noticing and directing such to reduce risk to campers. 2. Very limited infrastructure/materials are being placed within the floodplain. Access roads will be compacted and maintained to reduce erosion. Railroad ties and pavilion posts will be anchored. 3. Very limited infrastructure or materials are being placed within the floodplain. Access roads will be compacted and regularly maintained to reduce erosion. Railroad ties and pavilion posts will be anchored. 4. The property is currently used as an equestrian facility and ranch land. Neighboring properties appear to be ranching properties as well and significant development is not anticipated or zoned for the area. Primitive campsites do not seem to be incompatible with those current uses. S. Access to the site will be provided via County Road 245. The access entering and leaving the campground is located more than 10 feet above the 100 -year flood elevation. This access road is within 250 feet of the furthest campsite. 6. There are no public infrastructure or utilities located within or effected by this project and therefore governmental service costs are not expected to increase. 7. Very little information is provided by FEMA regarding the 100 -year flood in this area. The base flood elevation has been estimated to be falling from 5670 to 5668 over the project site. Base flood elevation was estimated by overlaying the Preliminary FIRM Panels 1105E and 1108E of 2011 with existing site maps and contour lines. The Preliminary FIRM Panels were compared with the effective maps and the floodplain appeared to have not changed between the two. The campsites will be located between elevations of 5666 and 5668. Campsite locations will be selected or modified to be slightly elevated to allow for drainage between and around. Therefore, during a 100 -year flood, campsites may be inundated between 1 and 3 feet. Expected velocities, duration, rate of rise, and sediment transport are unknown. S. Facility is not required to be a waterfront location. 9. The area was chosen for the campsite due to the presence of vegetation that provides shade. There are no other locations on the property that provide shade. 10. There are no changes identified for this area based on the Garfield County Comprehensive Plan 2030 Land Use Map, dated June 10, 2015. 4-203 Description of Submittal Requirements O. Floodplain Analysis. 1. Please find the attached Floodplain Specific Site Plan, prepared in NAVD 1988. Please note that the property is located within a Zone A designated 100 -year floodplain, and, therefore, no floodway information is available. The proposed floor elevation of the pavilion structure is shown and because it is not an enclosed structure it is not required to be elevated above the base flood elevation. 2. Non -applicable. Structure is not enclosed and not required to be flood -proofed. 3. Non -applicable. No residential construction or mechanical equipment proposed. 4. Natural drainage will be slightly altered by raised platforms to provide adequate drainage paths around camp sites. Covered pavilion will sheet flow to adjacent land and flow will not be concentrated. Roadway surfaces will be graded to allow sheet flow off roadway towards Elk Creek. Site will continue to sheet flow towards Elk Creek in the same manner as before. 5. Please accept this letter and the attached Site Plan as the engineer's report to address the standards in section 3-301.13-G. of the Garfield County Land Use Code. Based on this Floodplain Analysis, and on behalf of my client Simon Longacre of 4.1 LLC, I respectfully request your approval of a Floodplain Development Permit for 2101 County Road 245, New Castle, CO. Sinc rely, 1�p 6-. qot�� April B. Long, PE Colorado Watermark, LLC IDI Q:� 45388