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HomeMy WebLinkAbout0.2 Sopris Engineering - Response to Staff Recommendations 05.15.2007May 15, 2007 Ronald B. Liston Land Design Partnership 918 Cooper Avenue Glenwood Springs, CO 81601 Re: Reserve at Elk Meadows Development, Reply to Staff Recommendations of April 11, 2007 SE Job #: 25019.01 Dear Ron: This letter addresses the engineering concerns generated by the Planning Commission in their April 11, 2007 meeting to review the Reserve at Elk Meadows PUD Sketch Plan Application. Specifically addressed in this letter are the issues that the Planning Commission wanted resolved prior to the public hearing before the Board of County Commissioners. The Staff comments are shown below in italic text while our responses to those items are shown in bold text. The remaining engineering concerns will be addresses prior to submitting the Preliminary Plan. Staff Recommendation V11. 5. on Page 49 states: "The Applicant shall provide the 10% affordable housing unit requirement on site within the development." • Affordable housing has been added to the development as duplexes on lots 54-63 of the South Meadow. This new configuration is shown on the revised "P.U.D. Master Plan" Staff Recommendation VII. 9. on Page 49 states: "Prior to the public hearing before the Board of County Commissioners, the Applicant shall provide a letter from the Glenwood Springs Fire District that specifically approves of the internal road network, design and grade.'' • Sopris Engineering provided Ron Biggers at the Glenwood Springs Fire District with the information needed to review the internal roads and we have met with him regarding this issue. He has said he will provide a letter addressing the road design but we have not received it yet. Sopris Engineering will provide this letter to the County prior to the BOCC meeting. Staff Recommendation VII. 11. on Page 49 states: "Prior to the public hearing before the Board of County Commissioners, the Applicant shall provide an analysis that the road grade of "Street A" can exceed 8% using the standards in Section 9:37 of the Subdivision Regulations of 1984, as amended." • Street A is classified as a minor collector per the Garfield County Standards and therefore should have a maximum grade of 8%. Sopris Engineering has provided graphic illustration showing the road profile for Street A and where it exceeds an 8% grade. We are proposing a maximum 10% grade for the following reasons (based on criteria in section 9:37 of the Subdivision Regulations): 1. The current design has approximately 3200 feet of road at a grade of 10%. The resulting elevation change for that length of road at 10% is 320 feet. To achieve the same elevation change with an 8% road, the length of road would have to be increased from 3200 feet to 4000 feet (an 800 foot increase). An increase of 800 feet of road with an average disturbance area 40 feet wide would mean 32,000 Sq. Ft. of increased disturbance to the development. Increasing the length of Street A by 800 would also result in two more switchbacks to be able to avoid the property boundary and tie into the existing road design for the Upper Meadow. The added switchbacks and 32,000 Sq. Ft. of disturbance would be a significant increase to the disturbed land already proposed. From an emergency access standpoint, 10% is an 502 Main Street • Suite A3 ❑ Carbondale, CO 81623 ❑ (970) 704-0311 ❑ Fax (970) 704-0313 SOPRIS ENGINEERING • LLC civil consultants SE. JOB 25019.01 May 15, 2007 Page 2 acceptable grade, to redesign the road at 8% with two additional switchbacks is a much less desirable option. 2. Currently, using 10% maximum grade, the proposed design has centerline cuts of 8-10 feet and retaining walls approximately 10-20 feet high in spots. To follow the same alignment with an 8% grade would result in larger cuts and retaining walls than are currently proposed. 3. The excessive grades have been minimized in length to provide a safe design at intersections while maintaining access to all Lots. 4. The sections of Street A that are currently designed at 10% grade have significant southern exposure that will minimize snow and ice buildup by maximizing solar exposure. 5. While the proposed grades of 10% on Street A exceed 150 feet in length, they are not on a dead end and therefore do not require turnarounds for fire equipment requirements. 6. The 10% maximum grade proposed will still permit the transport of fire fighting water by the Glenwood Springs Fire District. Staff Recommendation VII. 16. on Page 50 states: "Prior to the public hearing before the Board of County Commissioners, the Applicant shall address the comments made by Mountain Cross Engineering regarding pressure zones and gallon usage." Exhibit H clarifies those items as follows: 1) The water demands that were estimated for the augmentation plan (350 gpd) differ from those estimated for the water system (450 gpd). These should be congruent or explain the rational behind the discrepancy. • The water augmentation plan (by Zancanella & Associates) included calculations for the irrigation system and potable system and assumed 1.5 EQR's for each residence at 350 gpd per EQR for a legal water supply of 525 gpd. The water system calculations (by Sopris Engineering) were designed to include an estimated peak flow of 450 gpd for tank and water line sizing. The two values are not congruent due to the irrigation calculations and one is for legal water while the other is for system performance design. 2) The project is proposed to have two pressure zones, with pressures ranging from 170 psi to 40 psi. Pressures of 170 psi are very high. Generally speaking 100 psi is a more realistic maximum for residential plumbing fixtures. More pressure zones or individual residential PRV's should be considered. • The water system has been designed with a pressure at the residences of approximately 150 psi which in our experience is standard in industry. If it is determined that the max allowable pressure should be 100 psi we can modify our design to include additional PRV's without affecting the system design (tank or mainline location). If you have any questions or need any additional information please give us a call. Sincerely, SOPR1S ENGINEE Chris J. B. -y, E.I.T. Design ngineer a� y Nichol, P.E. Principal Cc;