10 Glenrose Engineering Report.pdf — original pdf

Backup

1405 Hillmont Street Austin, Texas 78704 Phone: 512-326-8880 e-mail: lauren@glenrose.com April 3, 2024 Chair Claire Hempel Vice Chair Awais Azhar Secretary Greg Anderson Parliamentarian Alice Woods Board Member Patrick Howard Board Member Jennifer Mushtaler Board Member Felicity Maxwell Board Member Grayson Cox Board Member Adam Haynes Board Member Nadia Barrera-Ramirez Board Member Danielle Skidmore Board Member Ryan Johnson Board Member Alberta Phillips Board Member (ex-officio) Jessica Cohen Board Member (ex-officio) Candace Hunter Subject: Recommendation to Deny Zoning Request for Zoning Case NPA-2023- 0020.02_106 & 118 Red Bird Lane Dear City of Austin Planning Commission, I am writing on behalf of Bird Streets of Pleasant Hill neighborhood group to recommend denial of the requested zoning of CS-MU-V-DB90-CO-NP (Density Bonus 90 combining district) in the subject zoning case. My recommendation is based on my review of these documents: 2023; • Civil Site Development Plans for 5412 S Congress Mixed-Use dated December • City of Austin Master Comment Report for Case Number SP-2023-0495C, Revision # 00 dated February 26, 2024; • City of Austin Technical Memorandum regarding Drainage Pattern and Public Infrastructure around Your Property to Mr. Bradford Massingill III, dated September 25, 2023; • An Environmental Resource Inventory Waiver Request Form filed for the project and approved by Watershed Protection Department; Glenrose Engineering, Inc. Texas Board of Professional Engineers Number F4092 glenrose.com City of Austin Planning Commission April 3, 2024 Page 2 of 3 • Relevant maps and Geographical Information System (GIS) data regarding topography, soils, and drainage associated with the proposed zoning changes. Based on my review of these documents, the proposed project will contribute additional storm flows to local flooding. It will inadequately protect sensitive environmental features associated with the proposed development location. Contribution to Local Flooding The proposed project would be located within the Williamson Creek watershed, upstream and less than a mile west of Interstate Highway 35. Based on information submitted by the applicant, existing pervious area on the site is 1.94 acres, which constitutes nearly 72 percent of the site area. Under the proposed development plan, the pervious area would be reduced to 0.87 acres, which is only 36 percent of the site. Pervious areas allow storm runoff to infiltrate into soil. This infiltration reduces flooding and erosion. It sustains the natural flow of water into seeps, springs, and creeks between storm events. Rainfall infiltration into soil also sustains trees during drought and reduces peak urban temperatures. The project’s proposed flood detention would only reduce peak runoff by titrating stormwater from a concrete basin into the drainage system over a slightly longer period. The proposed flood detention would not mitigate increases in flooding and erosion due to the increased volume of runoff. Nor would it mitigate the loss of the existing rainfall infiltration, which supports a natural and healthy ecosystem. Failure to Perform an Environmental Resource Inventory The Austin Watershed Protection Department granted an Environmental Resource Inventory Waiver request by the applicant. An Environmental Resource Inventory is required, however, for any proposed development on a tract containing or within 150 feet of a potential or verified wetland feature (Austin Land Development Code §25-8- 121(B)(4). Glenrose Engineering, Inc. Texas Board of Professional Engineers Number F4092 glenrose.com City of Austin Planning Commission April 3, 2024 Page 3 of 3 Neighbors have observed an ephemeral stream and spring either adjacent to or traversing the proposed development site. Their observations are consistent with satellite imagery that shows an area of dense vegetation in the southwest corner of the site. Topographic contours are also consistent with the presence of a small stream, as indicated in the attached map. We respectfully request a recommendation to deny the zoning change until a thorough investigation of the site by an independent environmental scientist is completed. Such an investigation should include an inventory of wetland plants and examination of soils for the potential presence of wetland species that would indicate the presence of a Thank you for considering these potential impacts from the proposed zoning change. I hope that you will recommend denial of the requested zoning. spring. Conclusion Sincerely, Lauren Ross, Ph. D., P. E. President Glenrose Engineering, Inc. attachment Sealed on 3 April 2024 Glenrose Engineering, Inc. Texas Board of Professional Engineers Number F4092 glenrose.com