2017-02-21_REVISION - M1988112 ‎(3)‎

• Permit No: M1988112
• IBM Index Class Name: Revision
• Doc Date: 2/21/2017
• Doc Name: Request for Technical Revision
• From: Battle Mountain Resources, Inc.
• To: DRMS
• Type & Sequence: TR34
• Email Name: WHE
• Media Type: D
• Archive: No

Table 2.1 Hydrologic Design Input for San Luis South Diversion System by Basin
Data
Sub -basin A
Sub -basin B
Sub -basin C
Total Below C
Drainage Area (acres)
326
148
63
537
PMF Peak Flow (cfs)
2130
1307
545
3000
PMF Runoff Volume ac -ft)
131.4
59.6
24.6
215.5
500 -year, 24 hour Discharge (cfs)
705
529
220
792
100 -year, 24 hour Discharge cfs
384 1
290
1 118
1 405
Table 2.2 Hydrologic Design Input for San Luis South Diversion System by Reach
Data
Basin A -B
Basin B -C
Total Below C
PMF Peak Flow (cfs)
1995
2713
3000
1000 -year, 24 hour Discharge (cfs)
833
959
1001
500 -year, 24 hour Discharge (cfs)
666
762
792
100 -year, 24 hour Discharge cfs
314 1
340
1 405
For comparison, Table 2.3 shows the hydrologic data that were the basis for the original project
design compared to the 2015 hydrology update by DOWL. The available design documentation
for the existing storm -water diversion system is included in Section D.6.5.6 of the 112 Permit
Application Amendment Permit No. M-88-112 for the San Luis Project, dated September 1989
(BMRI, 1989). The summary on Table 2.3 shows that the original hydrology significantly
overestimated the PMF rainfall -runoff values compared to results from currently accepted
methodology for estimating these extreme events as described in Appendix B. In contrast, the
current 100 -year, 24-hour storm estimates predict about a 40 percent higher flow rate in the
system than was used as the basis for the original hydraulic design of the South Diversion
channel and Drop Structure.
Table 2.3 Summary of Original (1989) and Revised Hydrologic Design Parameters
( I ) General Storm PMP values from HMR55A
(2) 8 hour PMP by interpolation (8 -hour not provided in HMR55A)
(3) Basis for original PMP value was not found in project documentation (BMRI, 1989)
(4) Volume estimated by taking ratio of area of Sub -basins A, B and C (537 acres) to total contributing
basin area as reported in original documentation (830 acres) = 537/830 = 0.647 multiplied by total
PMF volume for entire basin as reported in original documentation (680 ac -ft), or 0.647 * 680 ac -ft =
440 ac -ft.
San Luis Project — South Diversion Ditch Drop Structure - Final Design Report 11
2015 Update
1989 Original
Data
Design
Drainage Area (Sub -basins A, B, and C)
537 ac
537 ac
10.72 in/6hr(')
PMP Estimates
13.43 in / 12 hr
(11.6 in / 8 hr)(2)
14 in / 8 hr(3)
PMF Runoff Volume Sub -basins A, B, and C)
215.5 ac -ft
440 ac-ft(4)
PMF Runoff Peak Flow Rates
Sub -basin A
2130 cfs
4725 cfs
Sub -basin B
1307 cfs
2497 cfs
Sub -basin C
545 cfs
1084 cfs
100 -year, 24 hour Precipitation Depth
3,34 in
2.90 in
100 -year, 24 hour Discharge at Drop Structure
405 cfs
292 cfs
( I ) General Storm PMP values from HMR55A
(2) 8 hour PMP by interpolation (8 -hour not provided in HMR55A)
(3) Basis for original PMP value was not found in project documentation (BMRI, 1989)
(4) Volume estimated by taking ratio of area of Sub -basins A, B and C (537 acres) to total contributing
basin area as reported in original documentation (830 acres) = 537/830 = 0.647 multiplied by total
PMF volume for entire basin as reported in original documentation (680 ac -ft), or 0.647 * 680 ac -ft =
440 ac -ft.
San Luis Project — South Diversion Ditch Drop Structure - Final Design Report 11