20251203-002: Arbor View Variance Staff Presentation — original pdf

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ARBOR VIEW SUBDIVISION 4316 FAR WEST BLVD C8-2025-0085.0A Mike McDougal Environmental Policy Program Manager Austin Development Services OUTLINE 2 Vicinity Map Variance Requests Property Data  Variance Recommendation Synopsis  Additional Considerations Site Constraints Variance Conditions VICINITY MAP  North of the river  Located between Loop 360 and Mopac 3 North NTS 4 North NTS PROPERTY DATA  Bull Creek Watershed  Water Supply Suburban Watershed Classification  Drinking Water Protection Zone  Located over Edwards Aquifer Recharge Zone 5 PROPERTY DATA  Council District 10  Steep topography  Predominantly slopes over 25%  Currently undeveloped PROPERTY DATA 6 SYNOPSIS 7  0.56-acre subdivision located approximately 0.4 miles west of the Far West Blvd and Mesa Dr  The property is unplatted North NTS SYNOPSIS 8  The applicant proposes to plat a two lot subdivision  One lot will be a Critical Environmental Feature lot and will not be developed  The other lot will be a single family lot North NTS Critical Environmental Feature Lot Single Family Lot SITE CONSTRAINTS  The property slopes to the north (away from the Right of Way)  The majority of the slopes are greater than 25% (50% to 80%) 9 North NTS Drainage Drainage SITE CONSTRAINTS  LDC 25-8-301 limits the construction of driveways on slopes over 15%  The applicant proposes to construct a driveway on slopes over 15% 10 North NTS Drainage Drainage SITE CONSTRAINTS  LDC 25-8-302 limits the construction of buildings on slopes over 15%  The applicant proposes to construct a building on slopes over 15% 11 North NTS Drainage Drainage SITE CONSTRAINTS  LDC 25-8-423 limits watershed impervious cover to 30% of net site area  Net site area = ~775 sq ft  30% x 775 sq ft = ~232 sq ft 12 North NTS  The watershed impervious cover limit is ~232 sq ft Drainage Drainage  The applicant proposes 3900 sq ft of impervious cover VARIANCE REQUESTS Variance requests are as follows: 13 1. Request to vary from LDC 25-8-301 to allow the construction of a driveway on slopes over 15% 2. Request to vary from LDC 25-8-302 to allow the construction of buildings on slopes over 15% 3. Request to vary from LDC 25-8-423 to exceed the 30% net site area watershed impervious cover limit and to allow 3900 square feet of impervious cover VARIANCE RECOMMENDATION 14 Staff does not recommend the requested variances, having determined that the required findings of fact have not been met. Specifically, in response to findings of fact LDC 25-8-41(A)(2)(c), the variance will create a significant probability of harmful environmental consequences based on the proposed construction on steep slopes, including: VARIANCE RECOMMENDATION 15 1. Construction on steep slopes generates and transports greater amounts of sediment during construction than shallower slopes. This is expected to negatively impact water quality. VARIANCE RECOMMENDATION 16 2. Impervious cover prevents water infiltration into the soil. Instead, water runs across the impervious surfaces, picking up pollutants and sediment. Pollutants and sediment drain to waterways and degrade water quality. Drainage occurs more rapidly on steeper slopes. VARIANCE RECOMMENDATION 17 3. Site stabilization and revegetation after construction activities have been completed are less feasible on steeper slopes. Ongoing erosion is more likely on steeper slopes. Development on the site will create a significant probability of harmful environmental consequences based on Code and Criteria. ADDITIONAL CONSIDERATIONS 18 The applicant proposes to build the development on piers to minimize site disturbance during construction and to reduce the environmental impact. Piers will be installed up to ~35 feet above grade to support a horizontal building foundation on the steep slope. Property located immediately to the west, north, and east was platted many years ago. Without the requested variances, the proposed subdivision is reasonably unbuildable. VARIANCE CONDITIONS 19 If the Environmental Commission votes to recommend the variances, City Staff offers the following 5 variance conditions: 1. Impervious cover shall be limited to 3,900 sq ft for Lot 1 and 0 sq ft for Lot 2. 2. Prior to issuance of the COA building permit, the applicant must have an approved COA site plan exemption to allow construction of detention of 3,900 sq ft of impervious cover and an easement. 3. The detention will be maintained in accordance with COA requirements. VARIANCE CONDITIONS 20 4. Slab-on-grade foundation construction is not allowed. The foundation and driveway must be constructed using piers. Any grading exceeding four feet of depth or construction on slopes exceeding 15% will require Land Use Commission variances in accordance with applicable Land Development Code regulations. 5. The design and construction of structures on the lot must be based on the recommendations from a slope stability analysis performed by a licensed geotechnical engineer, as verified by the City. 21 THANK YOU AND APPLICANT PRESENTATION