STATE OF CALIFORNIA CALIFORNIA NATURAL RESOURCES AGENCY DEPARTMENT OF WATER RESOURCES DIVISION OF SAFETY OF DAMS FILE INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam O'Shaughnessy Type of Dam Water is Dam No. 9-5 County _T_u_o_l_um_n_e_ _ _ _ __ Concrete Arch Type of Spillway Gated Side Channel 3 feet - -above 13 feet below dam crest. - - - - spillway crest and Weather Conditions Sunny and hot, 95 degrees F. Contacts Made Steve Thomazin w/ Hetch Hetchy Water & Power (HHWP). Reason for Inspection Annual Maintenance Inspection. Important Observations, Recommendations or Actions Taken Concrete damage on the crest and upstream railing has been repaired, as requested. Maintenance repairs to the spillway will be completed within the next year, as documented in previous inspection reports. A long-term project to rehabilitate the dam outlet works is currently in progress. Projected work includes the replacement of several outlet gates and valves, rehabilitation of the spillway drum gates, access and safety improvements, and concrete repairs. The upper outlet valves could not be cycled on this date because all HHWP operators were either sick or unavailable. Arrangements need to be made to fully cycle all eight valves in DSOD's presence at the next possible opportunity. The owner has not flushed the drains into the weir at Elevation 3565, but they are reported to be flowing freely. The owner still plans to address mineral buildup at the drains over the next two years. Conclusions From the known information and visual inspection, the dam, reservoir, and all appurtenances are judged safe for continued use. Observations and Comments Dam I walked the crest and the horizontal galleries of the dam, and inspected the downstream face and groins from the crest and abutments. The dam, abutment contacts, groins, and toe appear to be in good condition with no signs of instability or distress. The crest and face joints were in satisfactory condition. Minor spalling was visible at a few locations on the downstream face, as usual, but this is not considered a dam safety concern. Concrete damage on the crest and upstream railing has been repaired, as requested. Vegetation control at the dam was excellent. I walked three horizontal galleries and two vertical galleries, and found them all to be in satisfactory condition and well-maintained. Typical dampness, mineral staining, and calcification were present on the ceilings and walls and at many of the construction joints, but relief drains and side channels were clear. The owner has plans to address mineral buildup over the next two years. Spillway The spillway approach, concrete ogee weir, and downstream channel were clear and unobstructed. Visible concrete surfaces were in serviceable condition, with no serious defects. The previously noted concrete voids at the spillway crest and below the drum gates were apparently unchanged, and some exposed rebar was visible at the toe of the spillway ogee. Maintenance repairs to the spillway concrete will be completed within the next year, as documented in previous inspection \ )CJ_ lo\~'? \(fi reports. The spillway gallery and drum gate controls remain in good condition. p('D ,170/lb f'r D fu-r ~:s'tv1 fb I} .p / f 6 Inspected by Photos taken? Yes cc for DWR 1261 (Rev. 10/09) X No Owner/Book Date of Inspection Date of Report A. C. Roundtree 6/2/2016 6/23/2016 Sheet _1_ of 5 INSPECTION Name of Dam ,: DAM AND STATUS O'Shaughnessy Date of lnspection _ _ _ _6_/2_/_20_1_6_ _ __ Observations and Comments Outlet The dam is equipped with a total of eight valves; These valves have historically been cycled biannually by the owner, and they were last cycled in DSOD's presence on 5/27/2011 with the exception of valve #1, which did not have sufficient hydrostatic pressure. The owner was unable to cycle the valves on this date because all HHWP operators were either sick or unavailable. Arrangements need to be made to fully cycle all eight valves in DSOD's presence at the next possible opportunity. Seepage The downstream face and right groin were dry. Seepage of -1-2 gpm was visible along the left groin, as is sometimes observed at higher reservoir elevations. Dam seepage is measured by two Parshall flumes and one v-notch weir in the lowest gallery. Because of high releases, the lowest gallery was flooded, and the weirs were not read during this inspection. Instr. Instrumentation at this dam consists of two seepage flumes, one seepage weir, and sixteen survey monuments. The most recent instrumentation data was transmitted to DSOD on September 30, 2014, and was reviewed in the previous inspection report. The current instrumentation report is overdue. DWR 1261 (rev. 10/09) Sheet 2 of 5 INSPECTION Name of Dam ,: DAM AND RESERVOIR IN CER1 IED STATUS O'Shaughnessy Date of lnspection _ _ _ _6 _/_2_/2_0_1_6____ 1. Downstream face of dam. - 2. Spillway side channel. DWR 1261 (rev. 10/09) 3 - of Sheet - - 5 INSPECTION Name of Dam 'IED STATUS r DAM AND RESERVOIR IN CER' O' Shaughnessy Date of lnspection _ _ _ _6_/_2_/2_0_1_6_ _ __ --- - - ....- .. ----~ -" ~ - .... i~- - .. / ,,.. . - \ .... ---- ' • - ~ -- • . .,... ..... . ~ - 4. Typical exposed reinforcement at toe of spillway ogee. DWR 1261 (rev. 10/09) Sheet 4 of 5 STATE OF CALIFORNIA _ALIFORNIA NATURAL RESOURCES AGENCY DEPARTMENT OF WATER RESOURCES DIVISION OF SAFETY OF DAMS INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam O' Shaughnessy Dam No. 9-5 County _T_u_o_lu_m_n_ e _ _ _ _ __ Type of Dam _C_o_n_c_r_et_e_ _ _ _ _ _ _ _ Type of Spillway Water is 8 above feet Concrete side channel spillway crest and 8 feet below dam crest. Weather Conditions Sunn ----L-------------------------------~ Contacts Made Steve Thom azin, Mike Patterson, Chris Graham, and Kevin Bolter with SFPUC. Reason for Inspection Periodic Maintenance Inspection Important Observations, Recommendations or Actions Taken Spillway repair work documented in my January 5, 201 4 inspection report has not been completed . The own er will complete thi s work within the next three years. This is acceptable . I requested the owner make arrangements to exercise all outlet valves in our presence in Spring 201 5. I requested the owner flush drains which are being measured by the weir at e levation 3565-feet. The drains may be becoming less effective due to blockage from calcium deposits. The owner has not initiated a Consultant's study of the dam but has initiated a system wide risk assessment study. However, an investigation of the outlet works was conducted, and two consultant reports were given to me during the inspections recommending rehabilitation. A letter will be sent to the owner requesting a complete report on the investigation and a plan and schedule for completing any necessary rehabilitation work. Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for continued use. Observations and Comments The visible portion of the upstream face, crest, and downstream face were in satisfactory with no signs of instability or movement. The groins were inspected from the downstream toe and they appeared to be tight and in satisfactory condition. Minor spalling was noted at a few locations on the upstream and downstream faces, but this is not a safety concern. The crest and face joints looked tight. A were inspected inside the dam, and they were in satisfactory condition with no signs of distress. Some moisture, dampness, and calcium deposits could be seen at some of the joints, but nothing that would be a cause for concern. Spillway The approach, ogee weir, and downstream channel were clear and unobstructed. The gates were in the up position and the log boom was in place. The spillway gallery was inspected and the visible portions of the valves and related equipment to operate the gates appeared to be well maintained and in good operable condition. A detailed inspection of th e spillway was conducted during the last inspection. Overall, the spillway concrete was found to be in satisfactory condition, but maintenance repairs were requested. This work has not been finished; the owner plans to have it completed within the next three years, which ~ 0 1' I if 11 is acceptable. ~·~~ Inspected by Photos taken? Yes cc for DWR 1261 (Rev. 10/09) No Owner/Book X Date of Inspection Date of Report Param Dhillon 06/16/2014 09/11/2014 Sheet -1- of °'I\\ I \ 6r 3 INSPECTION C. JAM IN CERTh Name of Dam O' Shaughnessy STATUS Dam No. _9_-_5_ _ _ _ _ _ _~ Date of lnspection _ _ _ _ 6/_1_6/_1_4_ _ __ Observations and Comments Outlet The low-level outlet at this dam consists of a total of eight valves; , one All the valves were exercised during the 5127 /2011 DSOD inspection with the exception of All valves are cycled biannually as part of the dam's preventive maintenance program and SFPUC should notify DSOD in future when these valves are cycled. All valves need to be scheduled to be cycled in DSOD's presence in 2015, and I requested the owner make these arrangements. Seepage No seepage was noted along the right groin and on the downstream face of the dam. A minor amount of live seepage was noted along the left groin. This seepage is only observed when the spillway is in operation. Dam seepage is measured by two Parshall flumes, and one 90-degree Vnotch weir within the dam. The following readings were provided during the inspection: 1. 2. 3. 3500-North (Parshall): 7 inches, or -200 gpm 3500-South (Parshall): 10 inches, or -340 gpm 3565 (90-degree V-notch): 0.7-inches, or -1 gpm All readings are within the historical range for the dam and are considered normal. Instr. Instruments at the dam consist of two seepage flumes, one weir, and sixteen survey monuments. The latest data submittal was dated July 31, 2013, covering the data from 2001 to 2013. My review of the data is summarized below. Seepage: The dam has two 3-inch Parshall flumes and a single 90-degree V-notch seepage measuring weir that are named; 3500-North (Elevation 3500-feet within the North gallery-Flume), 3500-South (Elevation 3500-feet within the South gallery-Flume), and 3565 (Elevation 3565-feet within the gallery-Weir). Both flumes and the weir are measured monthly. The measured maximum seepage flow rates were -250 gpm, -430 gpm, and -1.5 gpm, respectively, during the review period of 2013. The measured minimums were -200 gpm, -190 gpm, and -<1 gpm, respectively, during the 2013 review period. Flows follow the reservoir water level and decrease during the late summer months. Weir 3565 has been showing a decreasing trend since 2003. This may be due to calcium deposit blockage with the internal drains that drain to this weir. These drains need to be flushed within the next few years so the full capacity of the drains is restored. The seepage has followed the trends of the past and remains within normal ranges except Weir 3565. Survey Monuments: No abnormal settlement or horizontal movement was noted from the submitted data. Settlement movements were minimal for the review period between 2001 and 2013. Settlement movements were negligible between 2012 and 2013. Horizontal movement between 2001 and 2013 are oscillatory nature and follow reservoir surface elevations. The maximum downstream movement during the 13 year period was 0.02-ft in the downstream direction. These values fall within acceptable limits. Conclusion: The available instrumentation data indicates the dam is performing satisfactorily. Weir 3565 has followed a decreasing trend, and the drains that flow into it need to be flushed. The current instrumentation network is judged to be adequate. DWR 1261 (rev. 10/09) Sheet 2 of 3 INSPECTION ( Name of Dam O' Shaughnessy JAM AND IN STATUS Dam No. _9_-_5_ _ _ _ _ _ _~ Date of lnspection _ _ _ _6_/_1_6/_1_4_ _ __ Observations and Comments Other: I inquired on the status of the consultants' study of the entire dam referenced in our June 1, 2012 and June 10, 2013 inspection reports. Mr. Thomazin stated he was not aware of such a study being completed, and he was sure the concrete cores discussed in the 2012 report were not taken, which I also did not see any evidence of during the inspection. Mr. Thomazin was aware of an investigation and inspection of the outlets works. During the inspection, he gave me two reports entitled "O'Shaughnessy Dam Outlet Works 2009 Investigation Plan Final", dated November 10, 2009 and "O'Shaughnessy Dam Outlet Works 2009 Investigation Plan Technical Memorandum Draft", dated December 23, 2009. The reports wells, the documented the investigation findings of 6 gates, the in the wells, the downstream valves , and the six outlet conduits. The report does not identify any immediate dam safety concerns, but recommends rehabilitation of the outlet works, including refurbishment or possible replacement of valves and concrete repairs in the supply wells and tunnels. The reports received during the inspection will be filed under 251.1. Not all information was given to me pertaining to the investigation, including inspection DVDs. A letter will be sent to the owner requesting submittal of a complete outlet works investigation report and a plan and schedule for completing any necessary rehabilitation work. DWR 1261 (rev. 10/09) Sheet 3 of 3 FI LE STATEOFCALIFORNIA CALIFORNIA NATURAL RESOURCES AGENCY DEPARTMENT OF WATER RESOURCES DIVISION OF SAFETY OF DAMS INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS 9-5 County Tuolumne O' Shaughnessy Dam No. ---------Gated Open Channel Type of Dam Concrete Arch Type of Spillway 75.4 feet below dam crest. Water is 59.4 feet _ __ be_l_o_w_ _ spillway crest and Name of Dam Weather Conditions Sunn - - - 1 - - - - - - - - - - - - - - - -- - - -- - -- - - - - - - - - - Con tacts Made Steve Thomazin and Mike Patterson with SFPUC. Reason for Inspection Special Spillway Inspection. Important Observations, Recommendations or Actions Taken A detailed inspection of the spillway was conducted. Overall, the spillway concrete was found to be is satisfactory condition, but repairs are needed. At a minimum, voids greater than %-inch or where there is exposed reinforced steel need to be repaired. This work is considered maintenance, and an application is not required. Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for continued use. Observations and Comments Spillway The spillway approach, control structure and downstream channel were clear and unobstructed. The log boom was in place and intact. All the spillway drum gates were in the down position. Vegetation management within the spillway was satisfactory. The concrete masonry deflection walls in the bottom section of spillway channel were in satisfactory condition. The entire spillway was closely inspected during this inspection. The majority of the concrete sections, within the spillway were sounded and no drummy concrete was found. Typical edge deterioration of the cold joints was noted at the majority of the joints. Voids were also noted at some of these joints. These voids do not extend through the concrete and are mostly superficial. A larger than normal void was found within the ogee section below , and the original copper waterstop was visible in this void. Exposed Steel reinforcement was noted within the ogee section below Gate 3. The upstream side of the spillway was inspected from the reservoir side. The majority of the visible concrete surfaces were in satisfactory condition with an exception of exposed reinforcement on the Gate 2. upstream side and a large void, below As previously noted in past inspection reports, spalled concrete section at control section on Gate 3 was observed from the crest of the dam. I requested this be repaired. The owner needs to repair all voids, particularly areas where there is exposed reinforcing steel. The areas where deterioration along cold joints and voids are less than %-inch, repairs will not be required at this time. However, repairs will be required in future if conditions worsen. This work is considered maintenance, and an application or DSOD approval of the work will not be required. Standard concrete repair procedures need to be followed. . \\~\.\A... \)~ \) ')_; Inspected by Photos taken? Yes cc for DWR 1261 (Rev. 10/09) X No Owner/Book Date of Inspection Date of Report ~~~,,~ Param Dhillon i,\ 11/06/2013 01/05/2014 Sheet - 1 - of 10 INSPECTION Of -AM AND RESERVOIR IN CERT I F ~ ..... J STATU S Name of Dam O' Shaughnessy Date of lnspection _ _ _ _ 1_ 1/_0_6_ /1_3_ _ __ Observations and Comments DWR 1261 (rev. 10/09) Sheet 2 of 10 I INSPECTION Of -AM AND RESERVOIR IN CERTIF~ ~ .J STATUS Name of Dam O' Shaughnessy Date of lnspection _ _ _ _ 1_1/_0_6_/1_3_ _ __ Observations and Comments 1. Spillway channel viewed from downstream end. Concrete masonry deflection walls on right of photo. DWR 1261 (rev. 10/09) Sheet 3 of 10 INSPECTION OF- -AM AND RESERVOIR IN Name of Dam O' Shaughnessy CERTIF~-J STATUS Dam No. 9-5 Date of lnspection _ _ _ _1_1_/0_6_/_1_3____ Observations and Comments 3. Spillway channel downstream of the bridge DWR 1261 (rev. 10/09) Sheet 4 of 10 I INSPECTION OF- -AM AND RESERVOIR IN Name of Dam CERTIF~-J STATUS O' Shaughnessy Date of lnspection _ _ _ _ 1_1/_0_6_/1_3_ _ __ Observations and Comments 4. Typical edge surface deteriorations in cold joints. 5. Void in ogee section below DWR 1261 (rev. 10/09) Gate 2, viewed from side. Sheet 5 of 10 INSPECTION OF- -AM AND RESERVOIR IN I CERTIF~-.J STATUS Name of Dam O' Shaughnessy Date of lnspection _ _ _ _1_1_/0 _6_/_1_3_ _ __ Observations and Comments DWR 1261 (rev. 10/09) Sheet 6 --- of 10 ( INSPECTION OF- ...,AM AND RESERVOIR IN CERTIFh.. .J STATUS Name of Dam O' Shaughnessy Dam No. _9_-_5__________ Date of lnspection _ _ _ _1_1_/0_6_/_1_ 3____ Observations and Comments 12. Close up of exposed reinforcement. DWR 1261 (rev. 10/09) Sheet 9 of 10 INSPECTION OF ...,AM AND RESERVOIR IN CERTIFh.. J STATUS Name of Dam O' Shaug hnessy Date of Inspection _ _ _ _1_1_/_0_6_/1_3____ Observations and Comments 13. Close-up of a void on the upstream side of the spillway, below Drum Gate 2. DWR 1261 (rev. 10/09) Sheet 10 of 10 STATE OF CALI FORNIA CALI FORNIA NATURAL RESOURCES AG ENCY DEPARTM ENT OF WATER RESOURCES DIVISION OF SAFETY OF DAMS FILE INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam O'Shaughnessy Type of Dam Water is Dam No. 9-5 County _T _u_o_lu_m_n_e_ _ _ _ __ Concrete Arch Type of Spillway Concrete Side Channel 53 feet - - below spillway crest and 69 feet below ---- dam crest. Weather Conditions W arm and Sunny Contacts Made Steve Thom azin, Ad am Mazurkiewicz, Mike Patterson and Kevin Bolter with SFPUC. Reason for Inspection Periodi c Maintenance Inspection Important Observations, Recommendations or Actions Taken I requested Mr. Thomazin to arrange an inspection of the spillways' drum gates, down stream side and the approach. The inspection will be scheduled for fa ll of 201 4. I requested Mr. Thom azin to submit th e findin gs of co nsultant's study of the dam and the res ults of the ROV study. He agreed to do so in nea r future. Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for continued use. Observations and Comments The visible portion of the upstream face, crest, and downstream face were in satisfactory with no signs of instability or movement. Groins were inspected from the downstream side via binoculars and they appeared to be tight and in satisfactory condition. Minor spalling was noted at few locations on the upstream face but is not a safety concern. The crest and face joints looked tight. All the galleries were inspected. Some moisture, dampness, and calcium could be seen in some of the joints but nothing that would be a cause for concern. Spillway gates were and The spillway was in satisfactory condition during this visit. The three appeared to be satisfactory condition. The log boom appeared to be in satisfactory condition . The spillway has not been closely inspected for some time. I requested Mr. Thomazin to arrange a close inspection of the spillway drum gates, downstream side and the approach. The inspection will be scheduled for late fall of 2014. inspected and a plan will be developed to repair these locations. The inlet wells, as observed from crest, appeared to be in satisfactory condition. The dam has valves through the face of the concrete gravity portion of the dam . T he type and size of each valve is described in the table below. The valves are number from top to bottom. Valve Size (in) Type Inspected by Photos taken? Yes cc for DWR 1261 (Rev. 10/09) No Owner/Book X Date of Inspection Date of Report Param Dhillon 04/03/2013 06/10/2013 Sheet 1 -- of · 2 INSPECTION Name of Dam O'Shaughnessy L. · DAM AND IN STATUS Dam No. _9_-_5_ _ _ _ _ _ _ __ Date of lnspection _ _ _ _ 0_5/_0_7_/2_0_1_3_ __ Observations and Comments A special inspection was conducted in 2011 to inspect operation of all valves. All valves were exercised and they operated satisfactorily, with exception of Valve #1. Attempts should be made to coordinate with the owner to exercise valve #1. Seepage No unusual seepage was observed along the groins or the downstream face of the dam. The 90degree v-notch weir was dry. The North and South parshall fumes measured 2.3-inch (-35 gpm) and 4.8-inch (-108 gpm). Instr. Instrumentation at the dam consists of three seepage measuring weirs and 16 pairs of survey monuments. The Instrumentation Summary Sheet (ISS) was updated in July 2003 and accounts for all instruments, frequency of reading and data submittals. The latest data submittal was dated February 7, 2013, covering the data from 2001 to 2012. My review of the data is summarized below. Seepage: Seepage is measured by three weirs at various elevations within the dam. The lower weirs at elevation 3500 feet are called South and North weirs and measure majority of the seepage. The South weir closely follows the reservoir. In 2010, the South weir measured -200 gpm to -448 gpm and North Weir measured -200 gpm. The seepage has followed the trends of the past and remains within normal ranges. A single 90-degree v-notch weir at elevation 3650 also measures seepage but is mostly dry. Survey Monuments: No abnormal settlement or horizontal movement was noted from the submitted data. Maximum horizontal movement between 2011 and 2012 was 0.03 feet at most of the monuments. Maximum vertical movement between 2011 and 2012 was negligible. The long term maximum horizontal movements from 2001 to 2012 were 0.02 feet, respectively. The long term maximum vertical movements from 2001 to 2012 were negligible. These values fall within acceptable limits. Conclusion: The available instrumentation data indicates the dam is performing satisfactorily. The current instrumentation network is judged to be adequate. DWR 1261 (rev. 10/09) Sheet 2 of 2