Valmont Butte timeline

1800s – Area used by Arapaho and Ute as camping, hunting and
burial site

1858-1859 – Pioneers arrive in Boulder Valley, a party of
miners make a base camp in the area

1860 – Valmont Butte is site of final communal antelope hunt
by about 400 Arapaho. First building, the Tommy Jones Stage Stop, is

1865 – Town of Valmont is platted, incorporating three
blacksmith shops, two general stores, one hardware store, two hotels, a school,
two churches, the offices of three doctors and three saloons on the west end,
known as “Devil’s Row.” Nearby Fort Chambers used as militia training site,
soldiers of which participated in Sand Creek Massacre

1873 – Land deeded for Valmont Cemetery, railroads arrive

1870s – Valmont Butte starts to be used as a stone quarry,
including some stone used to pave Blake Street in Denver, operating into the
early 1900s

1897 – Culbertson Mill constructed by the Pennsylvania Group
to process gold from the Big Five mines

1910 – Culbertson Mill closes

1915 – Colorado Brick Company constructs brickyard at west end
of butte

1924 – Public Service Company of Colorado purchases lakes
south of the property and builds a power plant

1935 – St. Joe Mining Company constructs the Valmont Mill as a
four-level gold and silver concentrating plant known as Boulder Sampling Works,
using ore from Jamestown district mines, but goes bankrupt after two years

1937 – Mill renamed the Crystal Fluorspar Company and
reconfigured to concentrate fluorspar, fails within a year

1941 – Allied (General) Chemical Company purchases property to
convert it to large-scale fluorspar processing from Burlington Mine near

1961 – Public Service Company expands its power plant, creates
Valmont Reservoir by building dam with gravel and earth from south edge of dike

1967 – Elevated radiation levels found at the butte and in the
well of a nearby property, similar results found in the area three years later

1971 – City of Boulder discovers radium-contaminated soil from
old Bleecker Mill near Third and Pearl, transports 1,500 cubic feet of soil to
Valmont Butte property. Mill converts to processing gold, mostly from Cross and
Caribou mines west of Nederland, by Hendricks Mining Company, which leases the
mill from Allied

1972 – State health department finds that Allied is pumping
tailings pond excess into the cooling ponds at Public Service Company power

1973 – Sheriff’s office claims Allied discharging chemicals
into ditch along Valmont Road; Allied closes mill due to drop in demand for

1976 – Tusco purchases property, re-leases to Hendricks

1980 – Colorado Brick Company announces it is selling 400,000
cubic yards of soil from the butte to the Varra Construction Co. to be used as
road base for Foothills Parkway.

1983 – In February, Strategic Metals announces plan to dump 25
tons of material per week from its tailings at Rocky Flats into the Hendricks
holding pond; that permission is revoked in April. State issues an unsigned
notice and claim against Allied claiming that the facility’s contamination
damages could cost “$50 million per release”

1985 – EPA drills two wells, 45 feet deep and 30 feet deep,
finds no groundwater, decides not to drill any of the other scheduled wells,
and decides to not take all of the scheduled soil samples. Reports indicate
mill ceases operation

1994 – Hendricks closes its office at the site, Valmont Butte
Corporation purchases property

1995 – County designates Valmont Butte as Natural Landmark

1998 – Late CU environmental studies instructor and
whistleblower Adrienne Anderson’s class performs records search and uncovers
property’s extensive contamination history

2000 – City of Boulder buys the property on Aug. 28 for $2.54
million, city council discusses its possible uses on Sept. 5, finishes an
environmental site assessment on Sept. 18, plans call for building a biosolids
recycling center and fire training center at the property

2001 – Two structures on the property determined to be
eligible for listing in the National Register of Historic Places

2005 – City officials back away from plans to construct
biosolids recycling center and fire training center at the site

2006 – City offers property to Trust for Public Land, deal is
not completed

2012 – Consolidation of
tailings ponds, additional prairie dog euthanization scheduled to begin in

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