Tech App 1 - Tuolumne Utilities District

Technical Appendix I
Lake Capacity
Phoenix Lake Preservation & Restoration Plan
Date: March 3, 2011 To: Ted Allen, P.E. (Tuolumne Utilities District) From: Sam Diaz, P.E. , Chris Hammersmark, Ph.D., P.E., Kevin Fisher Project: 10‐1019 – Phoenix Lake Preservation and Restoration Plan Subject: Phoenix Lake 2010 Bathymetric Survey and Volumetric Storage Update Approach cbec, inc. has performed a comparison of lake volumes for Phoenix Lake, based on topographic and bathymetric survey data collected in 2002 and 2010. AutoCAD Civil3D 2011 was used to create triangulated irregular network (TIN) surfaces from data collected in each of the surveys. The surfaces were analyzed individually to determine the incremental volume of storage per foot of elevation, as well as compared to each other to determine the change in elevation of the lake bed over the eight year period between surveys. Survey data were provided by Horizon Water and Environment (Horizon) for the 2002 and 2010 bathymetric surveys. The 2002 survey was conducted by Tuolumne Utilities District (TUD); 2010 survey data were collected by Erik Ohlson & Associates with assistance from TUD. These data sets cover a similar area that is denoted “Limit of 2010 Survey Data” on the 2010 Lake Survey Map. A TIN surface was made using the 2010 survey data. Additional data from the 2002 survey was provided by TUD (via Horizon) to cover the extents of Phoenix Lake. A TIN surface was made from this data to produce an overall 2002 lake surface to be used as the basis for the volumetric comparison. The overall 2002 lake surface TIN was manipulated and edited until it produced elevation contours similar to those shown in the Phoenix Lake Bathymetric Survey of 2002 developed by Condor. To develop the 2010 Lake Survey Map, as well as a surface for volumetric comparison of the 2010 data, the 2010 TIN surface was pasted into the 2002 overall lake surface TIN. Differences in elevation between the 2010 survey data TIN and the 2002 overall lake surface TIN were compensated for by projecting the edge of the 2010 survey TIN up or down to the 2002 overall lake surface TIN at a slope of 1:1. Volumetric comparison between the 2002 and 2010 lake surfaces was made by determining the lake volume in one foot elevation increments. Comparisons of lake volume for the lake as a whole, as well as for the East and West Pools, are presented in the Phoenix Lake 2010 Volume Update spreadsheet (Attachment A). Volumes were calculated up to 2378 ft, as this was the upper extent of the 2010 survey. Above this elevation, 2010 data were not available, so a comparison for these areas was not performed. Distinction between East and West pools was determined topographically by a ridge that exists in the lake bed. Survey data indicated a slight relocation of the ridge from 2002 to 2010. For the East and West pool volume comparison, the ridge as indicated by the data for each survey was used to determine the division between the two pools. C:\Documents and Settings\Kevin\My Documents\HORIZON\1_Projects\TUD_Phoenix Lake\Task 4_Lake\4.2_Capacity\Draft Deliverable\10‐1019_PL2010_Storage_Update_TM_030311.docx 3/3/2011 1 cbec, inc. Phoenix Lake Preservation and Restoration Plan 2010 Bathymetric Survey and Volumetric Storage Update An analysis of the change in elevation was performed to determine areas of aggradation and degradation in the lake from 2002 to 2010. A volume surface comparing the 2002 and 2010 lake beds was created using Civil3D. The surface was defined with 2D banding to describe increments of elevation gain or loss of the lake bed. Sedimentation Rates and Patterns The results of the 2002 to 2010 lake volumetric comparison are depicted graphically in the “Comparison of 2002 and 2010 Bathymetric Surveys” drawing. In general, the repeated surveys indicate that large areas of the East Pool increased in elevation by 0.1 to 1.0 ft. Similarly, the area of the lake near the spillway also aggraded by 0.1 to 1.0 ft. Small “pockets” of extreme erosion and deposition are shown on the east side of the Sullivan Creek delta (i.e., sandbar). These pockets of erosion and deposition may be due to lack of 2010 survey data in these locations, and accordingly the relatively coarse interpolation of the 2010 surface TIN. Alternatively, these pockets may be due to shifting of the sandbar at the mouth of Sullivan Creek. The origin of the “pockets” will be further investigated with field verification and discussions with the surveyors. The results of the 2002 to 2010 lake volumetric comparison are depicted in tabular format in Attachment A. The total change in storage between 2002 and 2010 was determined to be 23.0 acre‐
feet. This amounts to a sedimentation rate of 4,638 cubic yards per year between 2002 and 2010 assuming a constant annual sedimentation rate. This sedimentation rate is more than three times that estimated by previous repeated surveys of the lake. The influence of watershed hydrology on the sedimentation rate over the 2002 to 2010 period will be addressed in Technical Memorandum #1: Baseline Characterization of Watershed and Lake Hydrology. C:\Documents and Settings\Kevin\My Documents\HORIZON\1_Projects\TUD_Phoenix Lake\Task 4_Lake\4.2_Capacity\Draft Deliverable\10‐1019_PL2010_Storage_Update_TM_030311.docx 3/3/2011 2 cbec, inc. Attachment A. 2010 Phoenix Lake Volume and Storage Estimates. Lake Volume Calculation Summary
2010 Overall Lake Volume ‐ Summer (AF)
2002 Overall Lake Volume ‐ Summer (AF)
Difference in Lake Volume (AF)
600.2
623.3
‐23.1
2010 Usable Storage ‐ Summer (AF)
2002 Usable Storage ‐ Summer (AF)
Difference in Usable Storage (AF)
517.6
527.2
‐9.7
2010 Usable Storage ‐ Winter (AF)
2002 Usable Storage ‐ Winter (AF)
Difference in Usable Storage (AF)
108.3
118.0
‐9.7
Notes:
1) Summer condition corresponds to a lake water surface elevation of 2385 ft
2) Winter condition corresponds to a lake water surface elevation of 2379 ft
3) Elevations referenced to North American Vertical Datum of 1988
4) Values reported for elevations above 2378 ft. are beyond the extents of the 2010 survey and may not accurately reflect current conditions
5) Volumes for East and West pools are based on the Mid‐Lake Ridge alignment as surveyed in 2002 for comparison to previous storage estimates.
6) Dead pool elevation for East Pool set at 2377 based on low point in the Mid‐Lake Ridge.
7) Dead pool elevation for West Pool set at 2370 based 2010 topographic map. Usable storage below 2370 in the vicinity of intake tower is assumed to be negligible. 8) Dead storage occurs in East Pool, West Pool and Marsh Cells 2 and 4 (See "Marsh Volume Estimates" at bottom of page for details).
West Pool
Contour (ft.)
2385*
2384*
2383*
2382*
2381*
2380*
2379*
2378
2377
2376
2375
2374
2373
2372
2371
2370
2369
2368
2367
2366
2365
2364
2363
2362
2361
2360
2359
Volume (CY)
243508.9
217533.7
192029.0
166996.4
142445.9
118940.0
97765.5
78989.8
63975.3
52283.3
41996.7
32844.1
24892.7
17935.9
11929.1
7016.4
3379.3
1096.9
197.7
39.5
7.0
0.1
0.0
Calc'd Volume (CY)
25975.3
25504.7
25032.6
24550.5
23505.9
21174.5
18775.7
15014.5
11692.0
10286.6
9152.6
7951.3
6956.9
6006.8
4912.7
3637.1
2282.4
899.2
158.2
32.5
6.9
0.1
0.0
2010 Survey Data
Calc'd Volume (cu.ft.)
701332.0
688626.4
675879.7
662863.5
634658.5
571712.3
506944.7
405390.7
315683.5
277738.7
247120.2
214686.5
187835.8
162183.1
132643.2
98201.4
61625.6
24278.4
4270.1
878.3
186.3
1.9
0.0
Total Volume (gallons)
Total Volume (AF)
Difference in West Pool Total Volume, 2002 to 2010 (AF)
West Pool Winter Usable Storage (AF)
West Pool Summer Usable Storage (AF)
Calc'd Volume (Gal.)
5246314.2
5151269.5
5055917.8
4958550.4
4747562.8
4276693.9
3792199.9
3032525.1
2361470.1
2077624.6
1848582.7
1605962.0
1405105.4
1213210.4
992237.2
734595.8
460990.4
181614.6
31942.1
6570.2
1393.6
14.1
0.0
Difference (cu.ft.)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
‐40135.2
‐34181.7
‐32178.3
‐43626.6
‐57194.9
‐61045.4
‐62510.7
‐69443.7
‐76117.9
‐76962.7
‐68200.4
‐39721.6
‐12313.4
‐3256.2
‐2009.6
‐1154.0
‐571.9
‐219.5
‐36.7
49182347
150.9
‐15.6
56.2
146.6
Volume (CY)
268726.7
242751.4
217246.8
192214.2
167663.7
144157.8
122983.3
104207.6
87706.6
74748.6
63270.2
52501.8
42432.1
33214.3
24892.3
17407.6
10951.4
5818.5
2393.3
764.0
275.4
147.9
73.4
30.7
9.5
1.4
0.0
2002 Survey Data
Calc'd Volume (CY) Calc'd Volume (cu.ft.)
25975.3
701332.0
25504.7
688626.4
25032.6
675879.7
24550.5
662863.5
23505.9
634658.5
21174.5
571712.3
18775.7
506944.7
16501.0
445525.9
12958.0
349865.2
11478.4
309917.1
10768.4
290746.8
10069.7
271881.4
9217.8
248881.1
8322.0
224693.7
7484.7
202086.9
6456.3
174319.3
5132.9
138588.3
3425.1
92478.8
1629.3
43991.6
488.6
13191.7
127.5
3442.5
74.5
2011.5
42.7
1154.0
21.2
571.9
8.1
219.5
1.4
36.7
0.0
0.0
Total Volume (gallons)
Total Volume (AF)
West Pool Usable Winter Storage (AF)
West Pool Usable Summer Storage (AF)
Calc'd Volume (Gal.)
5246314.2
5151269.5
5055917.8
4958550.4
4747562.8
4276693.9
3792199.9
3332756.6
2617166.6
2318334.6
2174931.4
2033808.5
1861755.4
1680821.4
1511711.1
1303995.4
1036709.8
691787.5
329079.5
98680.2
25751.6
15047.0
8632.3
4277.8
1642.0
274.7
0.0
54260845
166.6
65.4
155.8
* Volumes calculated above elevation 2378 ft are based on 2002 survey data and may not accurately represent current conditions
East Pool
Contour (ft.)
2385*
2384*
2383*
2382*
2381*
2380*
2379*
2378
2377
2376
2375
2374
2373
2372
2371
2370
2369
2368
2367
Volume (CY)
528081.9
466670.6
407686.7
350450.7
295131.1
242549.7
194519.4
151068.6
114552.4
83880.9
57877.4
36559.2
19991.0
8356.5
2852.8
651.9
40.3
0.0
Calc'd Volume (CY)
61411.3
58983.9
57236.0
55319.6
52581.4
48030.4
43450.8
36516.2
30671.6
26003.5
21318.2
16568.3
11634.5
5503.7
2200.8
611.6
40.3
0.0
2010 Survey Data
Calc'd Volume (cu.ft.)
1658105.4
1592565.0
1545372.8
1493630.0
1419696.7
1296819.7
1173170.3
985936.9
828132.4
702093.4
575590.9
447343.0
314131.5
148600.2
59421.9
16514.0
1088.4
0.0
Calc'd Volume (Gal.)
12403457.2
11913182.7
11560161.3
11173099.3
10620041.3
9700859.9
8775900.1
7375300.7
6194844.3
5252009.8
4305707.4
3346349.5
2349860.7
1111603.6
444505.3
123533.1
8141.6
0.0
Difference (cu.ft.)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
‐21779.0
‐25578.2
‐35868.2
‐58317.3
‐54974.4
‐46100.9
‐35959.7
‐22840.1
‐18396.5
‐4094.3
‐42.1
‐7.4
Volume (CY)
540080.1
478668.8
419684.9
362448.9
307129.3
254547.9
206517.5
163066.8
125744.0
94125.1
66793.2
43315.1
24710.7
11368.8
4533.2
1486.5
193.5
1.6
0.0
2002 Survey Data
Calc'd Volume (CY) Calc'd Volume (cu.ft.)
61411.3
1658105.4
58983.9
1592565.0
57236.0
1545372.8
55319.6
1493630.0
52581.4
1419696.7
48030.4
1296819.7
43450.8
1173170.3
37322.8
1007715.9
31618.9
853710.6
27331.9
737961.6
23478.1
633908.2
18604.4
502317.5
13341.9
360232.4
6835.6
184559.9
3046.7
82262.0
1293.0
34910.5
192.0
5182.7
1.6
42.1
0.0
0.0
Calc'd Volume (Gal.)
12403457.2
11913182.7
11560161.3
11173099.3
10620041.3
9700859.9
8775900.1
7538218.6
6386181.9
5520321.5
4741950.0
3757585.7
2694718.3
1380600.0
615360.7
261147.7
38768.8
315.1
0.0
Attachment A. 2010 Phoenix Lake Volume and Storage Estimates. Total Volume (gallons)
Total Volume (AF)
Difference in East Pool Total Volume, 2002 to 2010 (AF)
East Pool Winter Usable Storage (AF)
East Pool Summer Usable storage (AF)
106658558
327.3
‐7.4
49.6
256.3
Total Volume (gallons)
Total Volume (AF)
East Pool Winter Usable Storage (AF)
East Pool Usable Summer Storage (AF)
109081870
334.8
50.1
256.8
* Volumes calculated above elevation 2378 ft are based on 2002 survey data and may not accurately represent current conditions
Overall Lake Volume Comparison
Contour (ft.)
2385*
2384*
2383*
2382*
2381*
2380*
2379*
2378
2377
2376
2375
2374
2373
2372
2371
2370
2369
2368
2367
2366
2365
2364
2363
2362
2361
2360
2359
Volume (CY)
771590.9
684204.3
599715.7
517447.1
437577.0
361489.7
292284.9
230058.4
178527.7
136164.2
99874.1
69403.3
44883.7
26292.3
14781.8
7668.3
3419.6
1096.9
197.7
39.5
7.0
0.1
0.0
2010 Survey Data
Calc'd Volume (CY)
Calc'd Volume (cu.ft.)
87386.6
2359437.4
84488.6
2281191.4
82268.6
2221252.5
79870.1
2156493.5
76087.2
2054355.2
69204.9
1868532.0
62226.5
1680115.0
51530.7
1391327.6
42363.6
1143815.9
36290.1
979832.2
30470.8
822711.1
24519.6
662029.5
18591.4
501967.3
11510.5
310783.2
7113.5
192065.0
4248.7
114715.4
2322.7
62714.0
899.2
24278.4
158.2
4270.1
32.5
878.3
6.9
186.3
0.1
1.9
0.0
0.0
Calc'd Volume (Gal.)
17649771.4
17064452.2
16616079.1
16131649.7
15367604.1
13977553.9
12568100.0
10407825.7
8556314.5
7329634.5
6154290.1
4952311.5
3754966.1
2324814.0
1436742.5
858128.8
469131.9
181614.6
31942.1
6570.2
1393.6
14.1
0.0
Difference (cu.ft.)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
‐61914.2
‐59759.9
‐68046.5
‐101943.9
‐112169.3
‐107146.3
‐98470.4
‐92283.8
‐94514.3
‐81057.0
‐68242.5
‐39721.6
‐12313.4
‐3256.2
‐2009.6
‐1154.0
‐571.9
‐219.5
‐36.7
0.0
2002 Survey Data
Volume (CY)
Calc'd Volume (CY) Calc'd Volume (cu.ft.) Calc'd Volume (Gal.)
808806.8
87386.6
2359437.4
17649771.4
721420.2
84488.6
2281191.4
17064452.2
636931.7
82268.6
2221252.5
16616079.1
554663.1
79870.1
2156493.5
16131649.7
474792.9
76087.2
2054355.2
15367604.1
398705.7
69204.9
1868532.0
13977553.9
329500.8
62226.5
1680115.0
12568100.0
267274.3
53823.8
1453241.8
10870975.2
213450.6
44576.9
1203575.8
9003348.5
168873.7
38810.3
1047878.6
7838656.2
130063.4
34246.5
924655.0
6916881.4
95816.9
28674.0
774198.8
5791394.2
67142.9
22559.8
609113.5
4556473.7
44583.1
15157.5
409253.6
3061421.4
29425.6
10531.4
284348.9
2127071.8
18894.1
7749.3
209229.8
1565143.1
11144.9
5324.9
143771.0
1075478.6
5820.0
3426.7
92520.9
692102.6
2393.3
1629.3
43991.6
329079.5
764.0
488.6
13191.7
98680.2
275.4
127.5
3442.5
25751.6
147.9
74.5
2011.5
15047.0
73.4
42.7
1154.0
8632.3
30.7
21.2
571.9
4277.8
9.5
8.1
219.5
1642.0
1.4
1.4
36.7
274.7
0.0
0.0
0.0
0.0
Marsh Volume Estimate**
**Estimate of Marsh volume and storage is based on 2002 survey point data and contour map
Cell 1
Cell 2
Cell 3
Cell 4
Sullivan Creek
This area includes a small terrace at 2380 ft, which was calculated as full depth from 2380 ft to 2385 ft. Surrounding it is a sloping area, which was calculated as a triangular prism, 5' deep.
Full Depth Area (sq.ft.)
Slope Area (sq.ft.)
Summer Vol. (AF)
Winter Vol. (AF)
52715
60585
9.5
0.0
This area includes a scour pond down to 2369.5 ft, a small terrace at 2378 ft, and a small amount of sloping at the north of the cell up to 2385 ft. Assumed full depth coverage from 2378 ft to 2385 ft
over the entire area of cell, ignoring a small sloping area.
Trapezoidal prism volume calc of pond (i.e., 1/2*(B1 area + B2 area)*H) plus 7' depth over full area of cell above the pond in Summer, 1' deep in Winter. Cell volume is only usable storage above
2378 ft, due to a ridge at that elevation on the south end.
Pond ‐ 2369.5' Area (sq.ft.) Pond ‐ 2378' Area (sq.ft.)
Cell 2 Area (sq.ft.)
Summer Vol. (AF)
Summer Us. Stor. (AF)
Winter Vol. (AF)
Winter Us. Stor. (AF)
7677
61271
106559
23.9
17.1
9.2
2.4
This cell includes a large flat area at approximately 2380.5 ft, then slopes up in the north to 2385 ft
2380.5' Flat Area (sq.ft.)
Slope Area (sq.ft.)
Summer Vol. (AF)
Winter Vol. (AF)
175310
278043
32.5
0.0
This cell includes a large, gently sloping area. Local variations in elevation made it easier to break it down into smaller regions of similar elevation for estimation
2380.5 ft Flat Area is a small flat area with base elevation 2380.5 ft. Full depth volume calculation up to 2385 ft.
Hole has a base elev. of approximately 2379.2 ft and slopes up on both sides to about 2381.5 ft, average. Triangular prism volume calc up to 2381.5 ft, then full depth up to 2385 ft.
Transition area has one bank at 2380.5 ft and another at 2381.5 ft. Assumed base of 2381 ft for volume calc.
Upper Marsh slopes from 2381 ft to 2384 ft at northeast end of marsh, with some high spots in between. Assume upper end elevation at 2385 ft to account for high spots.
TUD 2011 survey data in the northern portion of this cell was referenced as a check on slope and terrain.
2380.5' Flat Area (sq.ft.)
Hole Area (sq.ft.)
Transition Area (sq.ft.)
Upper Marsh Area (sq.ft.)
Summer Vol. (AF)
Summer Us. Stor. (AF)
Winter Vol. (AF)
Winter Us. Stor. (AF)
19089
21617
296924
342002
47.2
46.7
0.0
0.0
The beach is a small area with an average base elevation of 2380.5. Full depth volume calculation from 2380.5 up to 2385.
Sullivan Creek runs from elevation 2379.5 at the north end to 2379 at the pond. Assumed steep banks. Assume average bed elevation of 2379.25
Beach Area (sq.ft.)
Creek Area (sq.ft.)
Summer Vol. (AF)
Winter Vol. (AF)
10893
58536
8.9
0.0
Overall Marsh Summer Volume* (AF)
Usable Marsh Summer Storage* (AF)
Overall Marsh Winter Volume* (AF)
Usable Marsh Winter Storage* (AF)
122.0
114.7
9.2
2.4
* These volumes are estimates, based primarily on 2002 survey data
They apply to both 2010 and 2002 calculated volumes

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