120 Camino Alto, Marin County, California
The Biggio Brothers operated a private dump (landfill) from the 1920s until the 1950s with few government regulations on waste disposal. The city of Mill Valley acquired the property after the dump closed.
1920s – 1950s Mill Valley Dump
No record found of cleanup of the Mill Valley Dump.
1972 Mill Valley Middle School opens on top of a portion of the closed dump
1989 Heavy metals and arsenic are found in soil samples taken at the school
1991 Benzene, toluene, ethyl benzene, xylenes, antimony, arsenic and lead are in soil samples taken at the community center to be built next to Mill Valley Middle School. Plans for the center include softball and soccer fields.
1995 Methyl ethyl ketone, chlorobenzene and acetone are found in groundwater. Gases within the dump are measured at explosive concentrations.
1996 Pipes are installed beneath the newly built gymnasium addition at the Mill Valley Middle School to collect gases from the dump. The gases will be piped
to the roof level and released into the air.
1998 Methane gas is measured at explosive concentrations in soil samples taken from an area planned for the community center.
1998 Sports fields open on a portion of the community center site. Five newly installed modular classrooms at Mill Valley Middle School are equipped with alarms set to go off if gases from the dump reach explosive concentrations within the classrooms
1998 The Mill Valley Community Center opens. Pipes are installed beneath the buildings to collect gases from the landfill. Chemical gases are piped to the roof and released into the air. Alarms are set to go off if gases from the dump reach explosive concentrations within the buildings.
2008 Children and adults continue to play, work and attend schools on the Mill Valley Dump. Tamalpais Pre-Kindergarten, Tam Valley Elementary School and Mill Valley Middle School are all on a portion of the dumpsite.