 Ground was broken in 2003 on the site of an orchard ( 39 @.@ <unk> ° N 122 @.@ <unk> ° W ﻿ / 39 @.@ <unk> ; <unk> ) next to the main cloister building . Architect Patrick Cole of <unk> , overseeing the rebuilding project , said that there were more than half of the required stones for the chapter house . Of the missing stones , more than 90 % were repeating @-@ pattern stones with available templates to carve replacements . <unk> Oskar Kempf and Frank Helmholz used modern hydraulic lime as mortar rather than making their own as was done in the Middle Ages . Helmholz said of the opportunity offered by the project that it was " something most stonemasons don 't do in all their career . " 
