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HomeMy WebLinkAboutFile Documents.1310 Red Butte Dr.0114.2018.ARBK DENVER CARBONDALE DURANGO BOZEMAN WWW.DHMDESIGN.COM 311 Main Street, Suite 102 Carbondale, Colorado 81623 P: 970.963.6520 April 20, 2018 City of Aspen Community Development Department Attn: Jennifer Phelan RE: 1310 Red Butte Drive- Application for Bridge Repairs Jennifer, The owners of 1310 Red Butte Drive are seeking approval for improvements to the existing bridge on their property in order to address structural and safety concerns. The bridge has been evaluated by a structural engineer and does not meet current code related to structural loads and guardrail safety requirements. A letter and supporting documentation from Resource Engineering Group (REG) who performed this review has been enclosed in this application. REG has also provided a plan for the repairs to address these concerns. History The existing bridge is a non-conforming structure that was constructed at the time of the original development of the lot in the mid-1960s prior to the local requirements for a permit. The current owners are in the process of constructing a new single family home on the property (building permit 0018-2015-ARBK) and future repairs to address life/safety concerns were noted in the landscape plans for the stream margin exemption application approved in January of 2015. (See attachment). The project team has met on site to review the existing conditions with representatives from the Engineering Department ahead of submitting this application. Photo documentation of the existing bridge is attached. Based on the direction provided by Engineering, the project team has provided an estimate of the existing value of the replacement cost of the bridge as well as an estimate to construct the proposed repairs to demonstrate that the repairs do not exceed 10% of the value of the structure per the Code requirements in 26.312.010. The Estimates have been provided by Koru who is the current contractor for the residence. It is anticipated that Koru will also be the contractor for future repairs to the bridge. Design Approach Due to the 30 foot span of the bridge, and the poor condition of the structure, and original design not meeting current codes, the structural engineer has determined that the least impactful design approach would be to re- inforce the existing wood structure with steel. The design for the bridge repairs provided by REG will use the existing bridge foundations and will include bolting sections of C channel to the existing timber beams to address the structural issues. The color of the steel will be rusted, consistent with the current paint color on the bridge. Given the span of the bridge, the engineer has determined that it would be difficult to address the structural concerns using only wood. Additional piers and supports would be needed to maintain the same 04/24/2018 DENVER CARBONDALE DURANGO BOZEMAN WWW.DHMDESIGN.COM 311 Main Street, Suite 102 Carbondale, Colorado 81623 P: 970.963.6520 member sizing, which would mean additional mass within the floodway. The steel reinforcement will also provide a very durable long term solution. The existing wood decking is rotting and new wood decking will be used to replace this decking so that like materials are being used where possible. The existing guardrails are below code height and has gaps between the rails which are greater than 4”. It is our understanding that the building department may require that the guardrail be updated to meet current building code standards. The design team is currently proposing that the updated guardrail be constructed with steel in order to allow for the attachment onto the steel reinforced cladding of the bridge structure instead of attaching to the existing compromised wood structure. Welded wire panels (4”) could be used between the upper and lower rails in order to meet the code requirements while minimizing additional mass within the floodway. The design team is open to suggestions and recommendations from the zoning, engineering and building departments on the best way to proceed with the design of the guardrails in order to balance the need for safety with important floodway concerns. Environmental Considerations The improvements have been designed to have a low impact to the site and disturbance to areas adjacent to the bridge will be very minimal. Sections of C-Channel can be carried and installed by hand eliminating the need for any heavy equipment within the stream margin area. The existing concrete abutments will remain in place and the footprint will not be expanded, therefore a floodplain work permit should not be required. The approved landscape plans for the project include significant restoration re-vegetation work along the hillside and within the stream margin. Any disturbance due to the repairs would be addressed with this already planned and permitted restoration work. The design team has included a construction management plan to ensure that any environmental impacts due to the repairs and maintenance of the bridge will be controlled and mitigated. We are providing our submittal and supporting documentation in digital format; the following page includes a list of appendices by file number and name for your reference. The referenced files can be downloaded using this link for 14 days from the date of this memo. Thank you for considering this request. Please let us know if there is additional information you would like the project team to provide in support of this application. Regards, Jason Jaynes Principal, DHM Design 04/24/2018 DENVER CARBONDALE DURANGO BOZEMAN WWW.DHMDESIGN.COM 311 Main Street, Suite 102 Carbondale, Colorado 81623 P: 970.963.6520 1310 Red Butte Drive- Application for Bridge Repairs List of submittal documentation Note: all files are pre-pended with a two digit number which corresponds with the numbering of this list. 01 Bridge Application Summary Memo (this document) 02 Permit Application 03 HOA Form 04 Compiled photos of the existing bridge 05 Structural engineer’s letter of analysis of existing bridge 06 Proposed bridge rehabilitation drawings 07 Original Stream Margin Exemption Site Plan 08 Original Stream Margin Exemption Tree Mitigation Plan 09 1310 Red Butte Construction Management Plan 10 Bridge replacement estimate of cost 11 Bridge rehabilitation estimate of cost 12 Original 1310 Red Butte Stream Margin Exemption approval and development order 04/24/2018