FLOOD02650

• County: La Plata
• Stream Name: Animas River
• Basin: San Juan/Dolores
• Title: Hydrology Addendum to FIS La Plata County Unincorporated Areas
• Date: 5/21/2002
• Prepared For: La Plata County
• Prepared By: Montgomery Watson
• Floodplain - Doc Type: Floodplain Report/Masterplan

.
.
.
I.
I.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
,.
I.
.
.
.
.
.
'.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

topography of approximately a 2.5 mi reach of the Animas River in the vicinity of the James Ranch
property. The revised reach of the Animas River was originally studied in 1981 using detailed
methods and 1995 revisions also applied detailed methods. The March 16, 1995 revision to the
PIS is based upon the following documents:

. Floodway and Flood Elevations Modifications, Animas River, MP 78.940 to 81.419, La
Plata County, Colorado, Goff Engineering and Surveying, Inc., November 10, 1992.
. 1"=200', 2-foot contour interval topographic mapping by Goff Engineering and Surveying,
Inc., November 10, 1992,

The second revision to the original 1981 PIS was published May 21, 2001 to incorporate detailed
flood hazard infonnation for the following stream reaches:

. Animas River - 2.09 mi downstream of V.S. Highway 155/160 to 0.39 mi upstream of La Posta
Road.
. Animas River - 0.58 to 3.56 mi upstream of 32nd St.
. Lightner Creek - Confluence with Animas River to 3,525 ft upstream of V,S. Highway 160.

The 2001 revision is based upon 1994 2-foot contour interval mapping and peak-discharge
frequency relationships derived from the 1989 PIS for Durango and the 1995 PIS for La Plata
County unincorporated areas.

Community Response to the CWCB Desienation and Approval Process
A letter from the CWCB was transmitted to La Plata County regarding the Board's proposed
action for designation and approval of the revised La Plata County PIS. The County was
receptive to the Board's proposed designation action and provided verbal agreement for the
action in a July 2,2001 phone call.

4