liquefaction, liquefaction is a term they use when the ground is loose. usually when structures or infrastructure is built on sand or land fill, something that's not solid, what happens is in shaking, during an earthquake, the earth that's very loose, that sand or land fill, acts like water. this is sand, sand and water coming up through a hole. in japan, all these buildings were built on liquefaction. i forget what year this was, but it was one of the bigger earthquakes. 7 story buildings built on liquefaction. the amount of time the earth shook, the earth became liquid and as it became liquid, the building sank into it until it stopped. when it stopped it just fell over. light damage buildings, superficial damage, broken windows, some plaster that might be cracked but basically a light damage building would be one that has mostly damage to the contents. shelves falling over, windows broken, that type of thing. if you had to go into a light damaged building, you would use these procedures. of course you gather information about a building before you go i

it is all sold and liquefaction. >> treasure island is unique. it was originally developed to be the location of the world fair with the understanding that once it was finished, that would become the location of san francisco international airport. it is 11,000 feet long. in those days, the thought that was more than enough to land any conceivable airplane. they thought it was ideal. they said that we have all kinds of sand out in the bay from the sacramento river. we will take the stand out of the bay and create this island. the sand is loose and below the water. it liquefied in 1957. it liquefied in 1989 during the loma prieta. it was similar to what happened in the marina. >> as they move along and developed treasure island, the developer also has to provide stabilization programs. >> the sand has to be strengthened so that it will not liquefy. the buildings have to gain support below the sand in more confident material. >> we were talking about the waterfront. here's the very building. here is the intersection of the water and the land. the a

there was a lot of water damage we might have even had some liquefaction soil failure. we had a major failure. >> that's right. this tribute goes all the way to golden gate. this is in a mountain lake and beyond ththat, it was a surface flow. this is a reservoir. on my right is this defensive the positive dune sand. the wind blows, it comes from the ocean beach. because the sand is moving, you can see evidence along this side of the hill in 1989. the vibrations in accelerated. you have a significant amount of movement to the point that the homes that uc had very severe damage for two blocks. we recognized what the problem was at the time, it was a matter of loose sand on a very steep slope. thank you for the effort. we were able to get federal funding and design which you see in the upper walls. the lower walls was actually billed as part of the wpa. the upper wall was built in 1991-'92. this is a concrete wall and it has rocked going through the wall that extends the distance of 80 feet beyond the wall. the next earthquake occurs, the wall is designed to resist and the

it not only has liquefaction, but it also has a hillside stability issues. while it may be stable sporadically, when the earthquake comes, the slopes may fail. as a minimum, they should retain the services of a geotechnical and structural engineer, and there are well qualified people who come out. i am not just talking about and inspection service, i'm talking that licensed engineer, geotechnical, to look around, look at the maps available, and write an opinion letter as to the adequacy of the structure or the soil. there is another thing to consider when you are buying and building to the east of the van ness ave. a third map. this map depicts the area of the fire that followed the 1906 earthquake. the blue is where all the buildings were destroyed or badly damaged by the fire. as a result, the ashes from those fires remained on site. in those days, lead paint was used to paint the sides of buildings. it is a known carcinogen. it is a hazardous material. what they did was after the earthquake, they took these mounds of sand, the valencia st. hill, if you go

>> this area, the ground water is deep, so you do not have to worry about the liquefaction. you have to worry about the loose sand during an earthquake. we estimate between 2 inches and 3 inches of settlement. these piles will hold the building up and the ground will settle around the piles and not cause damage to the structure. they will screw this into the ground by using a combination of forces. it will push and twisted into the ground. the upper 20, 30 feet goes easily, and then it starts to tighten. then at some point, it could actually stop the pile. the resistance could be so strong that it will sure off the pile and that is when we stop. >> your firm or somebody here is a special inspector, paying attention to how this is done? >> that is correct. we are observing what is done. >> we get reports saying, yes, it a mess -- and met the requirements for here were the problems in this is how they fixed it. what are they doing? >> they are screwing it into the ground. these are the marks. for every foot, the steel guy is recording the pressure on the steel. about how many