2008-02-22_APPLICATION CORRESPONDENCE - C2008086 ‎(42)‎

• Permit No: C2008086
• IBM Index Class Name: Application Correspondence
• Doc Date: 2/22/2008
• Doc Name: PDEIS Appendix D Coordination and Consultation
• Media Type: D
• Archive: No

(b) General Tributary Characteristics (check all that a~ly):
Tributary is: ®Natural
^ Artificial (man-made). Explain:
® Manipulated (man-altered). Explain: Project area contains pipelines, gas wells, powerlines, man made
ponds, and roads. This area has been used for grazing cattle as well as an off-road recreation area.
Tributar}~ properties with respect to top of bank (estimate):
Average width: 2.11 feet
Average depth: 0.372 feet
Average side slopes: 2:1.
Primary tributary substrate composition (check all that apply):
® Silts ®Sands ^ Concrete
® Cobbles ®Gravel ^ Muck
^ Bedrock ®Vegetation. Type/% cover: variable 0 to 10%
® Other. Explain: Substrate is largely dependent on the tributaries location within the sub-basins. Drainage heads are sandy
and covered with perennial and annual vegetation. Basin confluences typically have more gravels and some cobbles with perennial vegetation
bordering a narrow flow path that will ocasionally have some annuals growing in it. Basin flats are generally areas of heavy silt deposition
dominated by woody perennials and scattered annuals.
Tributary condition stability [e.g., highly eroding, sloughing banks]. Explain: Banks are typically compact and erode only in
extreme events; however, some washes exhibit deep entrenchment and show signs of sloughing banks in meanders.
Presence of run/riffle/pool complexes. Explain: Tributaries tend to disperse and fan out in flat basins where water flows braid
out, divide, and form new discrete channels. Confined charnrels above and below flat basins show signs of periodic pooling with silt
accumulations.
Tributary geometry: Meandering
Tributary gradient (approximate average slope): less than 1% in basin flats and 1.5 to 30% in drainage basins.
(c) Flow:
Tributary provides for: Seasonal flow
Estimate average number of flow events in review area/year: 20 (or greater)
Describe flow regime: Flows are associated with precipitation events between the months April and October. Typically high
flow volumes are associated with October precipitation events; however, the spring runoff month of May contributed the highest average flow
volume in East Salt Wash over the gauging period of record. The East Salt Drainage is approximately 225 square miles of which approximately
151 square miles are pairt of the Book Cliffs that provides spring runoff flour elevations up to 8500 fl.
Other information on duration and volume: Discharges from storm events are localized into small drainages and are the result of
fast moving microburst storms. Spatial storm variation can produce runoff in one wash and none in another. Measured variability of
precipitation can be as much as 0.4 inches between small catchments within 0.5 linear miles of each other, resulting in a high variability of
discharge rates within a small area. This also results in a low level of continuous surface water connectivity between basins and the nearest
RPW. Average annual precipitation is 9.18 inches in areas south of the Book Cliffs and the percentage of precipitation to runoff ratios average
66% in neighboring washes.
Surface flow is: Discrete and confined. Characteristics: Combination of discrete, confined, and sheet flow.
Subsurface flow: No. Explain findings: Depth of impermeable Mancos shale (clay) to Dakota formation (sandstone) can be in
excess of 1000 ft, which is typically where water table is found.
^ Dye (or other) test performed:
Tributary has (check all that apply):
® Bed and banks
® OHWM6 (check all indicators that apply):
^ clear, natural line impressed on the bank ® the presence of litter and debris
® changes in the character of soil ^ destruction of ten•estrial vegetation
® shelving ® the presence of wrack line
® vegetation matted down, bent, or absent ® sediment sorting
® leaf litter disturbed or washed away ^ scour
® sediment deposition ^ multiple observed or predicted flow events
® water staining ^ abrupt change in plant community
^ other (list):
® Discontinuous OHWM.~ Explain: Distinct O HWM indicators are lost as channel flows are dispersed over basin flats.
The OHWM in down gradient channels are inconsistent.
If factors other than the OHWM were used to determine lateral extent of CWA jurisdiction (check all that apply):
6A natural or man-made discontinuity in the OHWM does not necessarily sever jurisdiction (e.g., where the stream temporarily flows underground, or where the
OHWM has been removed by development or agricultural practices). Where there is a break in the OHWM that is unrelated to the waterbody's flow regime (e.g., flow
over a rock outcrop or through a culvert), the agencies will look for indicators of flow above and below the break.
'Ibid.
WestWater Engineering Page 18 of 23 COE Jurisdictional Determination Request
DBMS 407