Robertson's El Cajon

Robertson's San Diego East County quarry
(known to them as San Diego Rock Plant #96)
has several ponds on this site.

One pond is visible from a road which goes to a local gun club.
The pond visible here extends quite a way to the right.

Rather than digging sand out of a creek or river bed, 
as a sand or gravel pit would do,
this quarry blasts rock out of a hillside
above the river.