ALP 16

surface water connection to CR213 is achieved during this time. period. Minimal staff will need to be
present during this period of the flow test.
4.1.3. Surface Water Connectivity
After the 7 day groundwater charge time period, flows will be released from Ridges Basin Dam at 100cfs
until the system has equilibrated. Prior to system equilibrium, a surface water connection to CR213
(and subsequently the Animas River) will be achieved. It important to record the time it takes for water
released from Ridges Basin Dam to reach CR213 and the Animas River. Minimal staff will need to be
present during this period of the flow test. Either Lisa Fotherby or other Reclamation employee will
note when surface flow reaches CR213 and will start to mobilize the staff from Denver who will be part
of the discharge measurements.
4.1.4. Equilibration
While the staff from Denver travels to Durango and the stage at CR213 continues to rise, a staff gage
reading should be taken and recorded at 30 minute intervals if possible. A staff gage reading fluctuation
of less than ±1 inch for 3 consecutive readings (1 hour time period) will indicate that equilibration
conditions have been reached. The time period for Equilibrium to be achieved is unknown and will be
answered during the release flow test.
4.1.5. Measurement
Once the system has equilibrated, there will be a series of measurements taken by two teams. One
team will be primarily focused on taking discharge measurements in Upper Basin Creek during the
100cfs steady flow conditions using the Stream Pro ADCP. If we do see a steady discharge at CR213 that
is significantly less than what is being released at the dam, a series of discharge measurements in Upper
Basin Creek will help identify locations where surface flow goes to groundwater.
The second team will take discharge measurements at CR213 as well as at the tributaries, if they are
flowing. In addition, the second team may also take discharge measurements at various locations in
Lower Basin Creek. Access and safety are two concerns for taking discharge measurements in Lower
Basin Creek. Steep banks, vegetation, and debris could make discharge measurements unfeasible for
lower basin creek, especially at the higher discharges. Discharges lower than 100 cfs may be more
feasible.
After 3 days of discharge measurements in Upper Basin Creek, a thorough 'map' of discharge at various
locations can be developed. Once the measurements of Upper Basin Creek have been made the first
team will head back to Denver. The second team will stay to measure discharges at CR213 under
different release rates from Ridges Basin Dam in order to develop a rating curve (stage- discharge
relationship) at this location. The rating curve will be used to calibrate the pressure transducer which
will be attached to one of the wingwalls of the culvert at CR213 (see section 5.2). The second team will
also be able to take discharge measurements of the tributaries, if they are indeed providing flow to
Basin Creek.