consultant walker. i want to clarify with director tumlin whether the contract and services for which mr. walker was retained to conduct this survey and this was his recommendations regarding service restoration is that concluded and the service concluded or ongoing? >> just one word of correction. chair walker's company had no role in the survey. that was done entirely in house by the staff. walkers term did analytics to shape options. i believe there may be some ongoing scope but for the most part the work that mr. walker's firm has done is complete. m.t.a. staff will carry it out. >> thank you, director tumlin.

i want to thank all of the folks who called in. it was very important comments. i want to make one final comment. something i was thinking about. in light of the discussion about shortened lines. in particular i appreciate ms. petty from senior disability action talking about she framed it transit first looking at transfer most which is interesting. i do think that it does highlight a real issue. i think that looking on the map of coverage it is easy to see a case for investment in core lines and requiring transfers and look like you are covering the city. i want to make sure especially as we look at the most

significant issue. winter 2022 changes are adopted, proposed and adopted and we are talking about if next step. i want to elevated i would like to see as clear as possible commitment to restoring the full length of these lines. remain a little concerned with the lack of clarity around the long-term plans. i appreciate further engagement before the shortening of the line would occur. i hope we can restore those lines. i think that the impact of forcing additional transfers is particularly harsh on senior and disabled riders, folks with mobility impairments. it i lengthens the trip for everyone. for all of us and any of us who

use muni regularly know that if you are planning a trip that involves one or two changes it completely changes amount of time you have to allocate. more can go wrong. it is a longer trip. the final piece. we can talk about this further offline. i think it is important to recognize forcing more and more transfers does not necessarily save us very much. there is this assumption that somehow it is 21 terminates at civic center and continues down market and there is a massive cost savings. at the level to come back right now i think it would be like one or two additional buses an hour required if you were to cover the entire lot.

one or two additional buses to run that line. which you can achieve by the 5 a few blocks away. you could run more buses. i pick up some of the extra folks there and a couple buses to serve the whole line. obviously, we have talked about trade-offs and moving parts here. when i looked into it i am surprised how low the savings seem to be by shortening these lines. it doesn't make sense short term when we have this usage and downtown traffic. there is a case for that. i appreciate that line coming back to understand the thinking of waiting. extension further downtown. i would like to see more clear

commitment that lines like this will run all the wayne downtown to original route as themuter track and workers getting down town. i hope we can get more clarity on that. those are my -- really my final thought beyond thanking everyone foreign gaugement. it is a long hearing. appreciate the m.t.a.'s responses to the question. the work that has gone into the recommendations and i want to thank everyone for their work and thank our operators and stafffor being here today. i don't see anyone else on the roster. if there are no further comments or questions, we can wrap this

up with those thanks. i would like to continue this item to the call of the chair again, especially since we have a series of recommendations that may go into effect in february. there may be a desire to bring this back one more time depending on the next rollout. mr. clerk call the roll on the motion to continue. >> motion offered by chair preston the hearing be continued to the call of the chair. vice chair chan. >> aye. >> mandelman. >> aye. >> chair preston. >> aye. >> mr. chair, three ayes. >> thank you. motion passes. thank you all again. please call the next item. 4. hearing to receive progress updates on the seismic retrofit options for 301 mission. based on public documents in our

file that being 160975. members of the public to comment on this call in the call-in number 415-655-0001. today's id24922118986. after you entered the id press pound twice and then star followed by number three if you wish to enter the queue to speak. >> thank you, mr. clerk. i am going to in a minute here hand it off to the sponsor of this item. before i do let me thank mr. peskin and the callers for their patience. it is a long hearing already. let me assure you that these items are not agendized in importance of order or order of

importance. we are looking forward to this hearing on this extremely important matter. thank you for your patience. i will turn the floor over to supervisor peskin. >> thank you, chair preston and supervisor chan and mandelman for the opportunity to bring this item before you. i wish that the 301 mission street mel enemy yum tower -- tower behind us but that is not the case. as you know, going back to 2009 when the first unit in that building were sold the tower had already begun to sink differentially, to tilt far beyond what the projections in the environmental analysis

yielded which is tropical. so far as this board of supervisors actually recently held a hearing on a different building and were concerned about the lack of seismic and geotechnical information in that report. in this instance over the life of the structure, there was projected to be four to six inches of uniform. the building not differential settlement, no tilt. this building like the one we considered the other day is in an area of town that was not originally tera fir mabut filled reclaimed lands. when i started the hearings in 2016 on the sinking and tilting, the building had already tilted

almost a foot and a half to the northwest and sunk approximately a foot. there was a lot of litigation which we are all aware of. that litigation has been settled. we don't know the terms of that. i am led to believe the homeowners association receive the range of individual homeowners received benefits. we do know that the city and county of san francisco did not participate monetarily but did make available at no charge the portions of the public right-of-way along mission and fremont streetses where a voluntary fix casing and tiling system that was supposed to stem the continued sinking and

tilting of the building and maybe even restore some of it and sadly, unfortunately, it would appear that the fix has exacerbated the sinking and tilting that is now approaching two feet of tilt at the top. i realize this has gotten a lot of media attention and is the issue. it is not what we are here for today. we are here, one, to hear why experts, structural and geotechnical experts think the fix caused the accelerated differential settlement. two, to hear from the department of building inspection who is the permit issuing authority and

their plans now and in the future as well as from the edrt, the design review team that has been a second be set of eyes for dpi, what their role has been, what their assessment of what went wrong in the fix and what their role is going forward. there is good news. the good news is and we will hear about this shortly. of 52-inch 36-inch casings on fremont and mission streets when work was halted in august 23rd there has been one test casing and it's would appear the techniques used for sinking that casing did not lead to any additional settlement. we will hear about that.

then colleagues we hope to have lessons learned. i have a series of questions you should feel free to jump in. obviously, this building is unique in san francisco because it is built out of concrete and not steel. 57% heavier. load is heavier. we know that the foundation system does not go to bedrock. it has 10-foot matt slabs supported by friction piles. you will hear about the column of sands and the substrate beneath the tower. with that the project that the fix is a product of the millennium homeowners

association. we will start with the hoa as to what the outcomes of the fix have been, what is going on with the building and what their plans are going forward. we will hear from the structural engineer of record who works for the hoa who participated in our 2015 hearings as well as matt who was the project manager for the hoa overseeing the construction doing the actual on the groundwork.

>> from this process it was unanimously endorsed by an independent third-party panel of experts after a peer review led by the university of washington. member of the berkeley academy

of alumni. once consensus was reached. the best approach in the foundation and long-term performance of the tower it was presented to the city's engineering design review team. after the review they also improved the design. in addition to seeking out the best available experts for the design the tower sought out most qualified team for construction. the lead design team of engineers from the mediation process were chairing over to the construction project itself. for construction only one obvious choice to select a contractor shimek construction. they have delivered on local projects such as bart, caltrains

and performed for the san francisco transit agencies. they sought out and relied on best experts and professionals to address the settlement of the tower. lastly, the tower has remained safe to engineering certainty. on this point there continues to be consensus. in the final declaration it was evaluated and determined to be structurally sound. that is why this is an upgrade not repair. after much consideration the millennium tower determined it was best to proceed with construction to improve long-term performance of the building. this including tilt construction, further projections over the long-term. on behalf of the tower community we are grateful for the engineers and construction professionals working with our

team to complete the upgrade. now with that backdrop i will turn it over to our lead engineer to update the board on the progress. >> good morning, mr. hamburger. >> good morning. i did attend to transmit a powerpoint this morning. i wonder if the clerk has that available. >> i did not get such a thing. i don't know if the clerk got it. >> through the chair to mr. hamburger, no, sir, i did not receive the powerpoint from you. i have a presentation from the department of building and inspection on this topic. >> i am sorry about that. if i can share my screen, i will share it. if not i will talk. >> we can help you share your screen.

if you can start with your bona fide des in this field. >> the screen is shareable now. i am ron hamburger. senior principal with simpson. i have approximately 47 years of experience in structural engineering. education, construction and failure investigation. i am a member of the national academy of engineering. past president of the structural engineers association of northern california. california and the national council of structural engineering associations. since 2011 i have chaired the follow veer committee of the american society of civil engineers that developed the structural engineering

requirements of the engineering code. if i may, i would like to talk briefly. supervisor peskin has about the problem and solution. millennium tire is constructed at the corner of mission and fremont street. like most of the financial district south of the market area of san francisco, underlying the city consists of artificial fill since the gold rush. young bay muddy possit is from the deposits when the san francisco bay covered that area. deep layer now 70 food down 70-f beach sand did not cover. [indiscernable] a very deep layer 150 feet of material called old lay clay. eventually about 230 feet down

formation bedrock. the tower like every building constructed in that part of san francisco prior to 2010 is a series of piles that extend down into the dens sand layer for the foundation support. the reason the building is settling is that under the effect of the building weight as supervisor peskin said is significantly larger than buildings constructed prior to that is causing a process called consolidation of the old bay clays beneath the building pile. consolidation is the pressure created by the building and by the watering of the surrounding site to allow construction of the adjacent buildings. basically squeezing water out of the old bay clay. that squeezes the water out it is like squeezing water out of a

sponge causing volume change that is allowing the site to settle. tilting beneath the building as shown in the slide is not uniform. the layers have different thicknesses on different sides of the site. construction add jay sent to the building including the transit center immediately to the southed removed the soils present to the construction and constructionrelieved pressure o. the building is tilting to the west. the goal of the voluntary upgrade is to arrest that perfected settlement of the building and to allow recovery over a period of years. we accomplished this by new

piles underneath the sidewalk on fremont and mission street at the side of the building. jack load off the existing foundation to new piles of rock and transfer that load down to the bedrock to stop the consolidation of the old clays. >> if we can go back a little bit. i know this is going back i recall it started on the mission site before the excavation and installation of the wall on the transbay terminal, and that was initially ascribed to more de-watering of 301 mission

street site than originally predicted in the earlier calculations and in further allegedly exacerbated by the de-watering of the transbay site. does that sound right to you? >> that is correct. it is settling since construction initiated on it. effect of de-waters is reducing the -- when you de-water it decreases the effect of waste of soils above or below the water table to create more pressure and consolidation. the building did not tilt until 2009 when it started on the add jays sent project it settled straight down.

>> my recollection is the same. >> as the structural engineer of record does that mean that you designed the foundation system or somebody else designed the foundation system? >> i was not the structural engineer of record for the original construction of the building. the original structural engineer of record designed the foundation system, they selected the number of piles to be used, how deep they would go, designed the foundation map on those

tiles, it was done on the basis of recommendation made by the geotechnical engineer of record for the original construction. >> remind he who is the structural engineer of record originally in the foundation system? >> original structural engineer of record was. [indiscernable] >> right, yes. >> tread will was the geotech? >> that's correct. >> going back again to the original if you will. >> was this a process in implementation failure? what do you think the original failure was in. >> i am not comfortable on this. i have not studied that in any

detail. my understanding is that the original geotechnical engineer for the project did under estimate the weight of one of the layers of soil. it was assumed when the project was originally discussed that the de-watering for this project was going to be only during the period of excavation and construction. . [please stand by]

>> digging piles 270' deep in the rock. with 36" diameter. once that's done, a 24" diameter steel pipe approximately 240' down through the center of those 36" diameter casings to the top of the rock and then they drill down into the rock and that's

another 30' and that's. once the pile is installed, they would totally be which is about 15' below grade in a 10' set. we have attached onto the existing and existing foundation will be basically extend that foundation out to

encompass new the contractor's technique and installing the 36" casings and the 24" casings. inadvertently removes soil from beneath the structure. and just squeezing the pile and resulting in volume changes. and piles have been installed and resulted in volume change