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Home My WebLink AboutC_Supplemental_Letter_250514 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone 425.415.0551 ♦ Fax 425.415.0311 www.riley-group.com April 23, 2020 Ms. Valery Kalashnikov Nord West Properties, LLC 13220 42nd Avenue East Tacoma, Washington 98446 RE: Response to Comments Aberdeen Townhomes 957 Aberdeen Avenue Northwest Renton, Washington RGI Project No. 2018-223 References: Encompass Engineering and Surveying, Preliminary Grading and Drainage Plan dated April 16, 2020 The Riley Group, Inc. Geotechnical Engineering Report dated November 27, 2018 Dear Ms. Kalashnikov: As requested, The Riley Group, Inc. (RGI) is providing this letter to respond to the City of Renton Comments dated January 10, 2020 Comment 1 f. Per RMC 4-3-050 (G)(2) steep slope and landslide hazard buffers shall be established by the geotechnical engineer. Section 4.6.6 of the Geotechnical Report states: “The proposed townhomes have been designed to step down with the existing topography and the majority of the development is on the least sensitive area of the site. Three townhomes are proposed on top of the slope outside of the sensitive slopes and setback from the slope. Based on the results of our subsurface explorations and slope stability analysis, the proposal will not increase the threat of the geological hazard to adjacent or abutting properties beyond predevelopment conditions; and will not adversely impact other critical areas; and the proposed development can be safely accommodated on the site”, however, the report references a previous site plan which shows the proposed buildings set back considerably further than the current site plan and does not take into account the drainage structures and retaining wall which is located on and around the steep slope. Prior to land-use approval, the geotechnical engineer shall provide a quantitative analysis of the steep slope and landslide hazard area and provide set- back based on the recommendations for the updated site plan and facilities being proposed closer than identified in the report. Additionally, a 15’ building set-back line (BSBL) will be required from the edge of the buffer, including the case that the buffer is determined to be 0’. Building, retaining walls and subsurface drainage structures shall not be located within the buffer or BSBL. Update the preliminary plans, geotechnical report and TIR to include any changes resulting in the buffer and BSBL and relocating facilities and/or buildings outside of this area. RGI Response: RGI completed a stability analysis for the currently proposed conditions as shown on the referenced plans and included the proposed drainage facilities. Per our recommendation, the retaining wall that was previously shown on the top of the slope has been removed and the grade changes will be accomplished with grading and the wall is not necessary except for the southwest corner and the wall is at the setback line. B B' A A' C C' 04/2020 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Aberdeen Townhomes RGI Project Number 2018-223 Date Drawn: Address: 957 Aberdeen Avenue Northeast, Renton, Washington 98056 Slope Stability Cross Sections Figure 1 Approximate Scale: 1"=60' 0 30 60 120 N = Slope stability cross section = Site boundary 1.6001.600 1 1 150.00 lbs/ft2 1.6001.600 Material Name Color Unit Weight l Strength Type Coheion l Phi Water Surface Ru Silty sand 125 Mohr-Coulomb 200 36 Piezometric Line 1 Silt 110 Mohr-Coulomb 400 34 None 0 Fill 125 Mohr-Coulomb 0 36 None 0 Safety Factor 0.000 0.250 0.500 0.750 1.000 1.250 1.500 1.750 2.000 2.250 2.500 2.750 3.000 3.250 3.500 3.750 4.000 4.250 4.500 4.750 5.000 5.250 5.500 5.750 6.000+ 27 5 25 0 22 5 20 0 17 5 15 0 12 5 -50 -25 0 25 50 75 100 125 150 175 200 Analysis Description Proposed Static A-A' Company Riley Group, Inc.Scale 1:311Drawn By ELW File Name Proposed Static.slimDate11/20/2018, 10:14:49 AM Project Aberdeen Townhomes SLIDEINTERPRET 6.009 1.6641.664 1 150.00 lbs/ft2 1.6641.664 Material Name Color Unit Weight l Strength Type Coheion l Phi Water Surface Ru Silty sand 125 Mohr-Coulomb 200 36 Piezometric Line 1 Silt 110 Mohr-Coulomb 400 34 None 0 Fill 125 Mohr-Coulomb 0 36 None 0 Safety Factor 0.000 0.250 0.500 0.750 1.000 1.250 1.500 1.750 2.000 2.250 2.500 2.750 3.000 3.250 3.500 3.750 4.000 4.250 4.500 4.750 5.000 5.250 5.500 5.750 6.000+ 27 5 25 0 22 5 20 0 17 5 15 0 -60 -40 -20 0 20 40 60 80 100 120 140 160 180 Analysis Description Proposed Static - B-B' Company Riley Group, Inc.Scale 1:290Drawn By ELW File Name Proposed Static B-B'.slimDate11/20/2018, 10:14:49 AM Project Aberdeen Townhomes SLIDEINTERPRET 6.009 2.0402.040 1 150.00 lbs/ft2 2.0402.040 Material Name Color Unit Weight l Strength Type Coheion l Phi Water Surface Ru Silty sand 125 Mohr-Coulomb 200 36Piezometric Line 1 Silt 110 Mohr-Coulomb 400 34 None 0 Safety Factor 0.000 0.250 0.500 0.750 1.000 1.250 1.500 1.750 2.000 2.250 2.500 2.750 3.000 3.250 3.500 3.750 4.000 4.250 4.500 4.750 5.000 5.250 5.500 5.750 6.000+ 30 0 25 0 20 0 15 0 -75 -50 -25 0 25 50 75 100 125 150 175 200 225 Analysis Description Proposed Static - C-C' Company Riley Group, Inc.Scale 1:374Drawn By ELW File Name Proposed Static C-C'.slimDate11/20/2018, 10:14:49 AM Project Aberdeen Townhomes SLIDEINTERPRET 6.009 1.1171.117 1 1 150.00 lbs/ft2 1.1171.117 Material Name Color Unit Weight l Strength Type Coheion l Phi Water Surface Ru Silty sand 125 Mohr-Coulomb 200 36 Piezometric Line 1 Silt 110 Mohr-Coulomb 400 34 None 0 0.2 Safety Factor 0.000 0.250 0.500 0.750 1.000 1.250 1.500 1.750 2.000 2.250 2.500 2.750 3.000 3.250 3.500 3.750 4.000 4.250 4.500 4.750 5.000 5.250 5.500 5.750 6.000+ 27 5 25 0 22 5 20 0 17 5 15 0 12 5 -50 -25 0 25 50 75 100 125 150 175 200 Analysis Description Proposed Seismic A-A' Company Riley Group, Inc.Scale 1:310Drawn By ELW File Name Proposed Seismic A-A'.slimDate11/20/2018, 10:14:49 AM Project Aberdeen Townhomes SLIDEINTERPRET 6.009 1.1731.173 1 150.00 lbs/ft2 1.1731.173 Material Name Color Unit Weight l Strength Type Coheion l Phi Water Surface Ru Silty sand 125 Mohr-Coulomb 200 36 Piezometric Line 1 Silt 110 Mohr-Coulomb 400 34 None 0 Fill 125 Mohr-Coulomb 0 36 None 0 0.2 Safety Factor 0.000 0.250 0.500 0.750 1.000 1.250 1.500 1.750 2.000 2.250 2.500 2.750 3.000 3.250 3.500 3.750 4.000 4.250 4.500 4.750 5.000 5.250 5.500 5.750 6.000+ 26 0 24 0 22 0 20 0 18 0 16 0 14 0 -40 -20 0 20 40 60 80 100 120 140 160 180 Analysis Description Proposed Seismic - B-B' Company Riley Group, Inc.Scale 1:281Drawn By ELW File Name Proposed Seismic B-B'.slimDate11/20/2018, 10:14:49 AM Project Aberdeen Townhomes SLIDEINTERPRET 6.009 1.3681.368 1 150.00 lbs/ft2 1.3681.368 Material Name Color Unit Weight l Strength Type Coheion l Phi Water Surface Ru Silty sand 125 Mohr-Coulomb 200 36 Piezometric Line 1 Silt 110 Mohr-Coulomb 400 34 None 0 0.2 Safety Factor 0.000 0.250 0.500 0.750 1.000 1.250 1.500 1.750 2.000 2.250 2.500 2.750 3.000 3.250 3.500 3.750 4.000 4.250 4.500 4.750 5.000 5.250 5.500 5.750 6.000+ 30 0 25 0 20 0 15 0 -50 -25 0 25 50 75 100 125 150 175 200 225 Analysis Description Proposed Seismic - C-C' Company Riley Group, Inc.Scale 1:374Drawn By ELW File Name Proposed Seismic C-C'.slimDate11/20/2018, 10:14:49 AM Project Aberdeen Townhomes SLIDEINTERPRET 6.009