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HomeMy WebLinkAboutMemo_Engineering Response Update 200915Page 1 MEMORANDUM To: Hailey Guglielmo, City of Aspen Engineering Department From: Richard Shaw and Carly Klein Date: September 15, 2020 Project Name: Gorsuch Haus Subject: Updates to Engineering DRC Applicant Responses This submission package is a follow up to provide additional information to the Gorsuch Haus DRC Applicant Responses, sent to Engineering on August 26th, 2020. This submission includes the following items: • Memo summary below on the west side grading and wall design requirements and design constraints, including grading plan design in the South Aspen St. ROW; • Sopris Engineering Memo regarding 16" Water Main Construction Sequencing with Exhibits A.1 and A.2; • Sopris Engineering Gorsuch Haus Cul de Sac Snowmelt and Surface Material Options Memo with Kwik Bond product data sheets These topics have required further detail through the Engineering review of the project and these memos are intended to provide that detail. Gorsuch Haus West Side: Grading, Civil Engineering, and Wall Design Existing conditions of the South Aspen Street ROW and the west side of the Gorsuch Haus include previously modified topography that is steep (20%) and falls toward the east, accommodating the existing mountain operations road, and falls to the north to the existing road surface. We have designed the walls to comply with mudflow requirements and to provide a functional cul de sac consistent with our Project Approval, that complies with City Engineering and Emergency Access Standards and is attractive for the public and community. The points below provide an expanded response to describe the factors and conditions that drive the grading design and wall relationships adjacent to and within the South Aspen Street Right-of-way (ROW) included in the Gorsuch Haus Detailed Review application. Key reasons for the proposed design: 1. Mudflow Mitigation Mudflow requirements establish the grade line and depth of the swale along the ROW and the adjacent grading. This swale flowline sets minimum wall heights along the public stair and the new cul-de-sac. Proposed improvements within the South Aspen Street ROW mitigate the potential mudflow, which has been analyzed consistent with the City of Aspen criteria. The mudflow is directed to a new swale along the west side of the Gorsuch Haus project and into an inlet that is proposed to replace an existing facility. The mudflow mitigation benefits existing properties in the neighborhood, including Shadow Mountain Townhomes and Gorsuch Haus. Landscape Architecture Planning Urban Design Strategic Services 120 East Main Street Aspen, Colorado 81611 970.925.8354 designworkshop.com Page 2 2. A new terminus to South Aspen Street The walls within the South Aspen Street ROW to accomplish an improved cul-de-sac are predicated on retaining the slope and required mudflow mitigation. The public is best served if the retaining walls are low as feasible, to avoid visual blocking of the corridor upslope. The South Aspen Street improvements completed as part of the Gorsuch Haus project provide neighborhood benefits like a new suitable and functional terminus to the street, new utility service features, and public access to Aspen Mountain. The exchange of a private portion of the Gorsuch Haus site for use of ROW allows the cul-de-sac to meet a 100ft diameter (Aspen City Standard) and include a new neighborhood sidewalk that allows movement around the street and ski slope. 3. Mountain Access South Aspen Street ROW serves year-round public access functions. The Project Level Review required public access from Norway Ski Run. The public walkway on the west side of the Gorsuch Haus should be as attractive as possible. Wall heights are therefore a concern – wall heights have been designed to extend the least amount above finished grade of the adjacent swale in the ROW as possible. Raising the west wall only serves to darken the public walkway space as higher walls for the public to pass though creates a “tunnel effect.” 4. Affordable Housing The affordable housing unit on-site is on the west side accessed from the public walkway – the livability of the unit will be degraded if the wall and adjacent grade is raised, further burying the housing unit below grade. The special review provisions in the Land Use Code seek to avoid the burying the Affordable Housing. A similar condition would exist for lodge rooms on the west facade, where increased wall heights would partially cover lodge room windows. Newly constructed accommodations should be quality oriented, to replenish the loss and age of the existing hotel rooms in Aspen not poor-quality lodge characteristics (reference lodging goals of the Aspen Area Community Plan). 5. Compliance with other review agencies Comments from Zoning and Building Departments focus on consistency with the approved Project Review with respect to both height compliance and life safety reasons for egress. These interior building requirements establish the doorway locations and elevations along the entire west and eastern sides of the Gorsuch Haus. Therefore, the nature of the grading in the ROW was anticipated in the Project Review Approved Plan Set. These points of egress by floor level are essential to the approved use of the site as a mixed-use lodge and meet International Building Code, and International Fire Code. 6. Consistent with the Project Review The Approval Ordinance #39 of 2016 established grading and we are very close to the proposed in the Detailed Review plan set, subject to a greater level of engineering that has occurred to accommodate the mudflow, surface water flow, and final cul-de-sac design. Building height and other parameters of the approval as well as zoning review, all rely on the grading embodied in Page 3 this approval. The Detailed Review plan set has endeavored to adhere to a consistent grading plan within the ROW from the approved plans. If you have need for future information, please advise the Gorsuch Haus Team and we would be pleased to discuss. Thank you for your time commitment to the Final review and the thorough DRC comments.