《新唐书·列传·卷一百四十七》
当初，成都城没有堑壕，庆复教卢耽挖护城壕，宽三丈，设置鹿砦，筑左右营寨，营寨分为五区，每区五十人，堑壕两岸种皂荚树，三年后树梢合拢。
初，成都无隍堑，乃教耽浚隍，广三丈，作战棚于埤，列左右屯营，营别五区。区卒五十，莳皁荚夹壕，后三年合拱。
At the beginning, there was no moat in Chengdu City. Qingfu ordered Lu Dan to dig a moat three feet wide, set up deer fences, built left and right camps, divided the camps into five areas, each with fifty people, and planted soapberry trees on both sides of the moat. After three years, the treetops grew together.