8268

• UCREFRP Catalog Number: 8268
• Author: Vaill, J. E.
• Title: Traveltime and Dispersion of Contaminants in the Yampa River from Steamboat Springs to the Green River, Northwestern Colorado.
• USFW Year: 2000.
• USFW - Doc Type: USGS WRIR 99-4239,
• Copyright Material: NO

EXAMPLE EXERCISE

The example form on this page can be used for the
example exercise. The form can be reproduced and used in
the event of a real spill.
Assume a pollutant spill of 2,000 pounds of a soluble
hazardous material into the Yampa River at Steamboat
Springs (site 2, fig. 1, table 3). One immediate concern
would be to determine the arrival time and peak concentra-
tion of the hazardous material at the Hayden water-treat-
ment plant, river mile 164.7 (site 10, fig. 1, table 3).
Step i.-By accessing the USGS Internet address
http://webserver.cr.usgs.gov (click on Colorado Water Data,
Surface Water, Station number 09239500), it is determined
that the discharge at streamflow-gaging station 09239500,
Yampa River at Steamboat Springs (fig. 1, table 1) is
1,000 cubic feet per second (ft3/s).
Step 2.-From table 4, for a discharge of 1,000 ft3/s,
the traveltime of the peak concentration between sites 2 and
site 10 would be 17.2 -1.3 = 15.9 hours.

Step 3.- The traveltime of the leading edge of the
hazardous material between site 2 and site 10 is determined
by multiplying the traveltime of the peak concentration
(15.9) by 0.89 = 14.2 hours.
Step 4.-From table 5, the unit-concentration value
(Cup) is 82.2 for a streamflow of 1,000 ft3/s at site 10.
Step 5.-Compute the most probable peak concentra-
tion at the Hayden water plant (site 10):
0.016 times 82.2 times 2,000 pounds divided by 1,000 ft3/s =
2.63 milligrams per liter at 15.9 hours after the spill.
Step 6.-Compute the time the trailing edge of the
spill would be expected to arrive at the water-treatment plant:
Divide 555.6 by 82.2 (Cup from step 4) = 6.8 hours after
arrival of the leading edge, or 14.2 (from step 3) plus 6.8 =
21.0 hours after the spill.
All of the above computations assume there is no loss
of the hazardous material between the spill and the intake.
Losses could occur by chemical reactions, volatilization,
adsorption on the streambed, or other processes.

Example Form

Step 1

Determine streamflow at spill location or site upstream from spill location (fig. 1, tables 1 and 3)
Determine (estimate) volume of spill in pounds
Determine points of interest (fig. 1, table 3)

ft3/S

Step 2
Determine traveltime of peak: concentration between points of interest (table 4)

hours

Step 3
Compute the traveltime of the leading edge of the hazardous material spill at points of interest
Traveltime of peak: concentration x 0.89 = hours

Step 4
Determine the unit-concentration value (Cup) from table 5

Step 5
Compute the most probable peak concentration at downstream points of interest
0.016 x (Cup) x (Volume) / (ft3/s) = mg/L

Step 6
Compute the traveltime of the trailing edge at downstream points of interest
555.6/ (Cup) = hours after arrival of the leading edge