725 Jamestown - SAC Meeting Minutes 2022_0606_Final for DBI.pdf

San Francisco Department of Building Inspection (DBI) MEETING MINUTES
Structural Advisory Committee June 6, 2022. 9:00AM to 1:00PM
Agenda / Meeting Minutes
1. ROLL CALL
Structural Advisory Committee Members Present:
John Wallace (Chair), DJ Hodson, Frank Rollo
DBI Members Present:
Janey Chan, Philip Chan, Willy Yau
Project Sponsor Members Present:
Nik Krukowski, Bryan Fat (Strada Investment Group); Jeff Fippin, Brooks Ramsdell (Engeo); Jeff Tarantino (Freyer & Laureta, Inc.); Bryan Cortnik (Daedalus)
2. MEETING PURPOSE
A Structural Advisory Committee (SAC) was formed to make a recommendation for the grading permit for 725 Jamestown Ave, as defined by SFBC Section 105A.6, to review the project and advise on matters pertaining to the design and construction of the project that may affect the slope stability of the site or create a potential for earthquake induced landslide hazards.
During review required under SFBC Section 106A4.1.4.4, the SAC shall verify that the project sponsor considered appropriate geological and geotechnical issues and proposed appropriate slope instability mitigation strategies, including drainage.
SAC review shall also consider other factors relevant to mitigate slope instabilities, including, but not limited to, ground slopes, soil types, geologic conditions, history of landslides in the vicinity, nature of construction, proximity and type of adjacent construction, and effects of the construction activity on the safety and stability of the subject property and properties within the vicinity.
3. DOCUMENTS REVIEWED
• Geotechnical Nov 20, 2018
• Supplemental and Slope Protection – Updated report May 5, 2022
• Engeo performed review of grading plan March 25, 2022 revision – April 4, 2022
• Architectural plans – Building 1 to 20 from HHJA – latest revision Dec 11, 2020
• Civil Plans – Street Improvements, Utility, Stormwater and erosion control Dec 17, 2020
• Civil Plans – Grading Permit, Retaining wall sections and details – Latest revision March 25, 2022
• Soil Nail Wall Elevations and details – Apr 4, 2022
• Jamestown April 4, 2022
• 833 Jamestown – prepared by Harold Lewis – Dec 1999 (Reviewed by Frank Rollo at DBI)
4. OPEN FORUM PUBLIC COMMENT
None.
5. 725 JAMESTOWN – Sponsor Presentation of (1) Geology; (2) Geotechnical; (3) Shoring
6. SAC PEER REVIEW ACTION ITEMS
Geology/Geotechnical Action Items
1. Engeo to make recommendation for how buttress dune sand can be cut. Provide temporary grading recommendations for cut slope angles. Depict the sand area as well as building fill. SAC does not believe a soil nail wall can be built in dune sand.
2. Engeo to represent bedrock strengths with C and Phi (Hoek Brown conversion to c and phi). John noted during the meeting they are reasonable and are only needed as backup.
3. Update assumptions to 2019 CBC (was using 2016 CBC).
4. Check wording on the minimum anticipated shoring heights if over excavation is needed.
5. Recommendations for either removing the artificial fill or using ground improvement techniques. Show the recommendations on plans.
6. Put rock strength into C and Phi and check design for soil nail wall Same as item 1.
7. Engeo to provide recommendation for how fill underneath building will be handled.
8. Address the impact of groundwater as you rework the fill if over excavation is planned.
9. Engeo to explain seismic design parameters Explain why 6” of deformation is appropriate for the wall. Will perform do an additional slope stability run for 2” of deformation to match the soil nail wall performance.
10. Engeo to make recommendation on temp wall design if over excavation is planned.
11. Engeo to provide sequence of design for building pad fill and dune sand fill, if over excavation is necessary.
12. Engeo to reissue their review letters for both grading and the soil nail based on the latest drawing revisions and on the appropriateness of a soil nail wall. Engeo to update peer review letter to reference latest plan set.
13. If alternative strategies are being evaluated, show alternatives for foundation support or ground improvement—these should be shown will they be performed and provide specifications on installation parameters (ie if gravel ram what is spacing? Etc. Or auger cast – provide details etc).
14. Soil nail wall review letters state we don’t recommend any portion of the design. Take a look at that statement. Need to state whether or not you believe a soil nail wall design is appropriate for this site. Engeo to reword limitation language to indicate soil nail is appropriate for the site.
15. Indicate the height of catchment fence and where is it located
16. Strength of catchment fence and bouncing of specific elements.
Civil Action Items
1. Share the SFPUC approved Preliminary Stormwater Control Plan with the SAC
2. Temp Erosion control plan was included as part of vesting tentative parcel map and should be shared with the SAC
3. Provide several sections through the site to present the relationship between the proposed soil nail wall, on site grading, Jamestown Avenue, and the existing affordable housing project to the north.
4. Verify grading conforms at edges – north/south in particular by providing additional grading details at property line. The additional grading detail will allow the SAC to validate the conform grading does not affect adjacent property uses
5. Drainage plan to be coordinated with the soil nail wall drainage and demonstrate how soil nail wall drainage is conveyed to the existing SFPUC infrastructure within Jamestown Avenue.
6. Erosion / sediment control plan – provide for review
7. Manhole should be plotted on Sheet 7 – Utility Plan
8. Civil to add notes on the plan indicating ground improvement or treatment/removal of artificial fill
9. Put together drainage design and show how the surface and back of wall drainage will tie into the city system
10. Provide confirmation of drainage infrastructure that controls runoff from being conveyed to the below grading parking serving buildings 17-20.
11. Provide stormwater runoff calculations to validate storm drain infrastructure capacity.
12. Provide a map and cross section showing the spatial relationship between debris, catchment, and freeboard between permanent retaining walls.
13. Would like to see cross section developed at Buildings 2, 4, 6, 8 and 18 and 20 that depict existing conditions, subsurface conditions, and final grades and building in relation to tie back walls. ENGEO to integrate geologic details into these sections.
Shoring Action Items
1. Daedalus to provide narrative of how buttress dune sand can be cut
2. Temp access road with 5ft width – provide a note on drawings for access road coordinate with civil drawings.
3. Detail 4 on sheet 3.4 to be cleaned up by Daedalus
4. Sheet 3.4 – change reference from Detail 4 to Detail 2.
5. Engeo to comment on embedment of GeoBrugg wall and any impact on soil nail wall. Coordinate footings at the end of the Geobrugg walls. Want to understand how it lays out on plan (since you run out of room on the north side due to PL and south side due to maintenance road)
6. Seismic design based on 6 inches of movement. Confirm if this movement acceptable to soil nail wall designer. If 6 inches what is impact on temp and permanent soil nail walls?
7. Risk analysis discusses temporary shoring that contractor should anticipate using shoring elements for any element that is over 6ft high. Change this to a minimum of 4ft or consider eliminating it altogether.
7. PUBLIC COMMENT
None. Request was made at 12:32 for public comment to hit *3 or raise hand; No public comments were made.
8. NEXT STEPS
Project sponsor will respond to the Action Items above and the SAC shall consider if another SAC meeting is needed or if the responses fully satisfy the Action Items which would allow DBI to continue their review of the grading permit for approval.