Just for the heck of it I just went to GOOGLE and did a search on Concrete "Casino Chips" I found the following,

Las Vegas Review Journal March 17, 1997
POT POURRI ... Bellagio construction workers recently stumbled onto four bags of Dunes casino chips buried at the site of the old Strip resort, according to a Bellagio worker. Years ago, Las Vegas casino operators buried chips in concrete when they were taken out of circulation. No word on the chips' fate. -- http://www.lvrj.com/lvrj_home/1997/Mar-17-Mon-1997/business/5034467.html

Web Site "Dive Las Vegas"
Trojan

The Trojan is a wooden boat about 35 feet in length located in the Boulder Islands area. This vessels is in about 50 feet of water and went down after being swamped during a storm in the early 60's. It is rumored that the boat was carrying discontinued casino chips that were being dumped in the lake. To this day, folks occasionally still find one or two if they are lucky!-- http://www.divelasvegas.com/divesites.htm

Las Vegas Life January 1999
"Years ago at the old Dunes hotel, when they changed chips, they threw the old ones on the ground at the site where they were going to build a new tower, and then they poured concrete over them," says Bill Akeman, -- http://www.lvlife.com/jan1999/atwork/story01.html

MT Democrat, 10/9/98
"When the Dunes Hotel in Las Vegas was demolished some years ago, collectors cruised the rim of the imploded structure, offering hundred-dollar bills to the construction workers for pieces of the rubble, in which old chips were embedded.

"Those collectors would then use dental tools to extract the chips from the chunks of concrete," McLendon said, shaking his head. -- http://www.mtdemocrat.com/news/chips102198.shtml