STATE OF CALIFORNIA CALIFORNIA NATURAL RESOURCES DEPARTMENT or WATER RESOURCES . DIVISION oF SAFETY OF DAMS INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Antelope Darn No. County Plumes Type of Darn Earth Type of Spillway Concrete weir and channel Water is 5.64 feet below Spillway crest and 28.54 feet dam crest. Weather Conditions Water surface Elevation was 4996.36 feet. Contacts Made Michael Anderson and_Vanesa Morones with DWR. Reason for Inspection Periodic Maintenance Inspection. Important Observations, Recommendations or Actions Taken The vegetation control was very good; however, there were a few small pine trees that need to be removed from the main and auxiliary dams. Conclusions From the known information and visual inspection. the dam, reservoir, and the appurtenances are judged safe for continued use. Observations and Comments Dams Main and AUXiliary dams The visible portions of the upstream slopes, covered with large riprap, were uniform and in good condition (see Photos 1 and 4). The riprap was stable and there were no gaps in coverage. The slopes were entirely visible and were uniform and in good condition (see Photos 2 and 5). The abutments were stable and the groins and toe areas were well defined and unchanged from the previously reported satisfactory conditions. The create, with a paved access road traversing them, were level and in good condition (see Photos 3 and 6). All of the historic thermal cracks in the road were appropriately sealed. There was a scattering of chipmunk activity, but no burrows in the dam were observed. The vegetation control was good; there were some new pine trees noticed at each dam. The operations and maintenance team normally clears these dams of this kind of vegetation at least once a year for continued satisfactory control. Sgillway The entrance area was clear of debris and in satisfactory condition. The log~boom was invplace and in satisfactory condition. The spillway exit channel was clear of debris, and the concrete throughout was in satisfactory condition. The concrete repair work located at several transverse construction joints along the spillway invert was holding-up well. During the inspection, no additional areas were identified to be in need of repair. Outlet gate reportedly performed without incident when it was last fully cycled in our presence an in July of 2011 and May of 2016, respectively. The two ?vaives reportedly operated without incident when they were last fully cycled on September 6, 2016. During the inspection, all of the valve erators were inspected and they appeared to be in dependable opera ?n condition. The performed well when it was exercised during the inspection. The valve reportedl erformed without incident when it was last fully cycled in our presence on August 8, 2013. band in satisfactory condition. Mr.? inspected by Alan Van Metre Photos taken? Yes No Date of Inspection 9/23/15 4"9 cc for Owner/Book Date of Report 10/28/2016 own 1261 (Rev. 10109) Sheet 1 e. 1c?.lv?ilb Name of Dam INSPECTION . DAM AND RESERVOIR IN .. .ED STATUS Antelope Dam No. 1-50 Date of lnspection 9/23/16 Observations and Comments Seeoage DWR 1261 The main. dam has 12 marked points of longstanding damp areas, as shown in Figure 1 of the latest Some of these areas initially appeared soon after the first filling of the reservoir. Three of the more notable seepage areas are located on the dam at about mid- height near the right abutment, along the lower portion of the left groin, and at the toe. During this inspection, the only live flow (a trickle flow at the Station 18+00 drain pipe weir) can be seen in Photo 12. All of the historic damp areas appeared to be similar to past reported conditions, with no live flows. At the?house, release flows were temporarily shut off to drain the pooled water covering the left and right headwall weep holes. There was no discernable seepage at any of the weep holes, which are probably blocked. However, there was seepage coming from around the lower portion of the left wall at an approximate rate of 109pm. This seepage appeared to be clear and unchanged from previously reported conditions. is working on a project to capture the seepage at the toe of the dam and eliminate the weep drains. At the auxiliary dam, the slope, toe, and groins were dry. The weir, which measures the combined flow from two seepage pipe exit portals, had a measured head of 0.07-feet, which corresponds to a flow of about 1.53 gpm. The left pipe was flowing at about 1.53 gpm, and the right pipe was dripping. This seepage condition was normal and within historic limits. Monitored instrumentation at this site consists of 6 embankment crest survey monuments, 66 spillway survey monuments, 18 open stand i iezometers, 11 observation wells, 1 embankment face drain, 6 weep holes, 1 seepage wei and 1 spillway under drain. The latest Dam Safety Surveillance and Monitoring Report was issued in May of 2016. The report includes historic data and new data for the period dating from January 1, 2015 to December 31, 2015. The survey monuments are surveyed at least once every three years and were last surveyed on January 28, 2015. The next survey will be performed no later than 2018. There are four survey monuments on the main dam crest? There are two survey monuments on the crest of the auxiliary dam_ Graphs of the vertical and horizontal movement data were provided with total historical movement dating back to 1971. Additional graphs of the vertical and horizontal movements were provided with data dating back to 2005. There have been insignificant incremental movements of less than 0.2?inches at all the monuments since 2005. The largest total vertical movement of 0.63?inches of settlement occurred at?and the largest recent incremental vertical movement of 0.08?inches of heave occurred at The lar est total horizontal movement of 0.47?inches in the direction occurred at *and the largest recent incremental horizontal movement of 0.08?inches in the direction occurred at The most recent centerline survey was performed in 2013. 5,025.3) was at Station 28+00, which is 0.3 feet abovethe e3 gn eva ion . . The survey monuments on the spillway crest, invert, and left and right walls have been monitored since 1970. From 1970 to 2006, the monuments were surveyed at least once a year. Since 2006, the monuments have been surveyed at least once every 3 years. The largest total movement of 0.83-inches of heave was recorded at (rev. 10/09) . Sheet 2 of 1 0 Name of Dam INSPECTICN DAM AND RESERVOIR IN 5. STATUS Antelope Dam No. 1-50 Date of Inspection 9/23/16 Obsewatiok DWR 1261 4.4- A The standpipe piezometers and observation wells are monitored quarterly. The reservoir has remained above approximate Elevation 5988 since 1979 and the range of the annual reservoir elevation changes has remained on average within about 12 feet. At the main dam, there are 10 standpipe piezometers_ There are 7 observation wells and 5 standpipe piezometers There are 3 observation wells? The-standpipe piezometers have been fairly stable throughout the data set with only minor changes that have corresponded well with changes in the reservoir elevation and precipitation events. The 10?year plots indicate no unusual trends. The observation wells and standpipe piezometers that monitor?have been very stable throughout the data set. Since about 2000, and OW-6 have been trending up approximately 7-feet and should be closely monitored for continued increases. Water levels in the shallow piezometers P-21 B, P-22 have remained near their tip elevations, which suggest somewhat dry conditions located above the assumed phreatic surface determined by the 1985 stability study. The 3-observation wells have been monitored since 1980 and have shown a very slight increasing trend throughout the data set of about 2.0 feet. The water levels in these wells appear to remain above the assumed phreatic surface determined by the 1985 stability study, and therefore should be monitored closely. At the auxiliary dam there are 2 Standpipe Piezometers to monitor and there is 1 Observation Well (OW-9) and 1 Standpipe Piezometer The standpipe piezometers have been monitored since 1983. Throughout the data set, the-piezometers have shown normal attenuated elevation changes that have correlated well with the annual cycle of reservoir elevation changes. In the shell, Observation Well (monitored since 1967) and Standpipe Piezometer have been stable throughout the data set. There were no problems indicated by the data. Graphed seepage data at the main dam consists of 6 weep holes at the left and right headwall of the valve house and a drain exit at Station 18+00 on the sl0pe. The 6 weep holes have been regularly submerged by outlet releases which shows up as gaps in the monitoring data. The periodic data indicates that the center weep hole on the left side wall generally has the most flow, which can range from 0 up to around 20 gpm. The Station 18+00 Drain has been monitored since 1984 and has been relatively dry with one spike (4 gpm) recorded in 1998. The auxiliary dam seepage has been monitored since 1984 and has ranged from 0.0 up to about 34 throughout the years. The average seepage is approximately 4 gpm. During the inspection it was measured at 1.53 gpm. The spillway underdrain has been monitored since 1984 and has been essentially dry throughout the data set with sporadic recorded flows of less than 5 gpm. However, there was one recorded spike (75 gpm) during the 1989 season. This spike reportedly was due to a crack in the spillway, which was subsequently repaired. 7 The data from the May 2016 Dam Safety Surveillance and Monitoring Report indicated that the two dams performed satisfactorily during the January 2015 thru December 2015 time (rev. 10/09) Sheet 3 of 10 INSPECTION DAM AND RESERVOIR IN STATUS Name of Dam Antelope Dam No. 1-50 Date of inspection 9/23/16 Observations and Comments frame. The instrumentation at this site is judged satisfactory. No additional instrumentation appears to be needed at this time. The are submitted annually and the next submittal is expected by May 2017. Other DSOD is working with to follow up on recommendations by the 2012 Directors Safety Review Board, such as overtopping during the PMF. The seismic stability issues have been resolved. DWR 1261 (rev. 10/09) Sheet 4 of 10 INSPECTION DAM AND RESERVOIR IN ED STATUS Name of Dem Antelope Dam No. 1?50 Date of Inspection 9/23/16 Photo 2. A View of the slope of the main dam as seen from the left abutment. owe 1261 (rev. 10mg) Sheet 5 of INSPECTION DAM AND RESERVOIR IN ED STATUS Name of Dam Antelope . Dam No. 1-50 Date of Inspection 9f 23/ ?l 6 Photo 3. A View of the crest of the main dam as seen from the left abutmentPhoto 4. A View of the upstream slope of the auxiliary dam as seen from the right abutment. own 1261 (rev. 10:09) Sheet 6 of 1D INSPECTION DAM AND RESERVOIR IN STATUS Name of Dam AHIEIODB Dam No. 1-50 Date of Inspection 9/23/16 Photo 6. A View of the crest of the auxiliary dam as seen from the left abutment. DWR 1261 (rev. 10x09) Sheet of _10_ INSPECTION DAM AND RESERVOIR IN 3D STATUS Name of Dam Antelope Darn No. 1-50 Date of Inspection 9/23/Photo 7. A View of the spillway entrance area, which was clear of debris and in good condition. ?w?VT-v? v? . W133.- ?2 I '1 Photo 8. A View of the spillway exit channel as seen from the bridge crossing. DWR 1251 (rev. 10309) Sheet 8 of 1D INSPECTION DAM AND RESERVOIR IN ED STATUS Name of Dam AHIEIQPQ . . Dam No. Date of napecti0n_ 9L2?f16 (rev. 10x09) Sheet INSPECTION DAM AND RESERVOIR IN 5D STATUS Name of Dam ADIQIQPE . i Dam No. 1-50 Date of Inspectim'l 9/23/16 126'] (rev. '1 0109) ?776 STATE OF CALIFORNIA CALIFORNIA NATURAL RESOURCES AGENCY DEPARTMENT OF WATER RESOURCES DIVISION OF SAFETY OF DAMS INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Darn AntEIQpe Dam No. l:5_0_ County Emma; Type of Dam earth? Type of Spillway ancrete weir and Channel Water is 8.4 feet IJEIOW spillway crest and ?:31 .fi feet below dam crest. ws ~4993 6 feet Weather Conditions _Sunny and mild Contacts: Vanessa Morones, Kevin Wright, Joe Eades, Jim Scarboroug?.h Luis Sepulveda, Mike Contacts Made Anderson Nick George, and Barbara Holbrook with OFD and HQ. Reason for Inspection Annual inspection Important Observations, Recommendations or Actions Taken as successfully cycled through full travel during the inspection. - Continue to monitor the seepage areas for unexpected changes in flow volume or turbidity. To this and, (MM has developed a reference map of seepage loactions. The map is updated at least yearly. - Complete additional clearing and shaping of the channel from the outlet house to the stream measurement weir to eliminate the high tailwater conditions at the outlet energy dissipater. . The source of the leakage around the outlet house training walls should be investigated. If the weep drains are the problem. they should be cleared, or replaced. - A number of recommendations were made by the 2012 Director?s DSRB. One recommendation is to determine the cause of the rising piezometer reading at P-22, which is located at mid-level on th slope. is working on a plan to address this issue. This effort and an update seismic stability analysis will be coordinated with DSOD. - Repair the shoulder erosion at the crest survey monuments. Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for continued use pending resolution of the above recommendations and those by the 2012 Director's Safety Review Board. Observations and Comments Mn The crest was in good condition, and the roadway asphalt cracks remain sealed. The embankment Dam appeared to be stable. The upstream rock protection was sound and well distributed. The slope was in good condition. See photographs 1 and 2. Vegetation and rodent control along the embankment and groins was good. Da_m The crest was in good condition, and the roadway asphalt cracks remain sealed. The embankment appeared to be stable. See photograph 3. The rock protection was sound and well distributed. A small amount of erosion is occurring along the left groin, but not enough for action at this time. Vegetation and rodent control along the embankment and grains was good. Spillway The spillway is shown in photographs 3, 4, and 5. The approach walls and ogee crest were stable and the concrete remains in satisfactory condition. The long standing, tight vertical cracks on the approach training walls were stable and not offset. The bridge deck and abutments appeared to be in satisfactory condition. Inspected by WPennington A Photos taken? YES ND Date of inspection 9/16/15 cc for Owner/Book Date of Report 9/28/15 ~14 ownizsirav. force) Sheet 01? INSPECTION Qr- DAM AN. RESERVOIR IN CERTIFIED STATUS Name of Dam Antelope Dam No. 1-50 Date of Inspection 9/16/15 Observations and Comments The concrete along the chute floor and walls remains in satisfactory condition. No significant offsets, deflections, or concrete deterioration were observed. Concrete patches along the chute floor remain sound. None of the wall drains were flowing, as expected. The very jointed rock beyond the flip bucket remains stable, but should be inspected following significant releases. Outlet appeared to be in satisfactory condition. It remains a permit required confined space. Therefore, a rescue team was stationed? before the gate was cycled through full travel. valve was cycled through full travel for a DSOD engineer during the 8/22/14 inspection. Seepage The embankment, abutment, and toe seepage patterns were similar to those observed in recent years. The seeps along the lower left groin remains. As before, saturated soil and standing water were observed along the lower part of the groin, photograph 2. The area of emerging vegetation shown in the photograph should be cleared again to improve seepage monitoring. Water continues to see alon a zone at mid-level on the ri ht side of the main dam. A mossy pool As in the past, small wet areas were present on the lower right part of the embankment, about 10 t015?feet above the toe. These areas have been noted in the past and do not have visible flow. has developed a map of seepage locations on the main dam that is updated at least yearly and is scheduled for an update in the near future. No seepage was observed along the auxiliary dam embankment, groins, or foundation. The toe drain was flowing about 2 gpm, which is within the normal range. The weep holes at the outlet training walls were submerged, photograph 6. As a result, the seepage weirs cannot be read, and the seepage that passes the training walls is difficult to monitor. Additional clearing and shaping of the channel from the outlet house to the stream measurement weir is needed to eliminate this condition. In addition, the source of the leakage around the training walls should be investigated and the condition of the weep drains should be verified. Sheet 2 of 9 INSPECTION Qr DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Antelope Dam No. 1-50 Date of Inspection 9/16/15 Observations and Comments The latest monitoring report is the 2014 In addition to visual monitoring, seepage monitoring and settlement measurements, the surveillance program includes 15 piezometers and 10 observation wells at the main dam and 3 piezometers and 1 observation well at the auxiliary dam. The main dam piezometer and observation well readings vary within a narrow range and generally remain below the assumed phreatic surface for the 1985 stability analysis. However, seepage along the face of the dam has been an issue for many years. The elevated readings at the slope piezometers, P-22, P-21B, and observation well seem to reflect this condition. These piezometers were checked for reliability and seem to be functional. A number of recommendations were made by the 2012 Director?s Safety Review Board. One request is to determine the cause of the rising piezometer readings at embankment P-22, which reads the phreatic surface in the shell, near the right abutment. is working on a plan to address this issue. They will also perform and updated seismic stability analysis which takes into account the latest data about the phreatic surface. The plan will be provided to DSOD for review and comment. The piezometer and observation well readings at the auxiliary dam remain stable and near, or below, the phreatic surface used for the 1985 stability analysis. Vertical movement at the crest of the embankments has been minimal and appears to have stabilized. Accumulated horizontal movement of the crest monuments has been small and appears to be stabilizing. The shoulder erosion at some of the crest survey monuments, Station 17+00 for example, should be repaired. No significant movement has occurred along the spillway monuments, although monument 43 (10+87) along the right spillway wall has been rising somewhat erratically for a total of 0.5 inches since the first readings were taken in 1971. Based on my field inspection, discussions with staff, and a review of the 2014 data, the dam appears to be functioning satisfactorily, pending resolution of the issues described. Sheet 3 of 9 INSPECTION 0r DAM AND RESERVOIR IN STATUS Name of Dam Antelope Dam No. 1?50 Date of Inspection 9/15/15 yam?! I. The main dam crest road, upstream rock slope? The slope appeared to be stable and the rock sound. A small amount of vegetation on the will be removed. DWR 1261 (rev. 10:09} Sheet 4 of 9 INSPECTION 0r DAM AND RESERVOIR IN STATUS Name ofDam Darn No. 1-50 Date of Inspection 9116/15 2. The erest road, slope and abutments of the main dam are shown. The lower left abutment seepage is visible. The low, reemerging vegetation within the oval should be removed to allow better visual seepage monitoring. This area was saturated, with small pools of standing water, which is nOI'maIly the case. DWR 1261 (rev. 10MB) Sheet 5 of 9 INSPECTION Or DAM AND RESERVOIR IN CERTIFIED STATUS Name of Darn Antelope Darn No. 1-50 Date of Inspection 9/1611 5 3. This view from the right abutment shows the overall con?guration of the auxiliary dam and its relationship to the spillway, arrow, and main dam in the background. The crest asphalt at the auxiliary remains sealed. The dam was stable appearing and the rock sound. Minor vegetation removal is needed at the upstream left groin. No rodent activity was observed. DWR1261 (rev. 10/09) Sheet 6 of 9 INSPECTION OI- DAM AND RESERVOIR IN STATUS Name ofDam Antelope Dam No_ 1-50 Date of Inspection 9/15/1 5 4. The spillway crest structure remains stable appearing and in satisfactory condition. No signi?cant concrete defects were noted, and the vertical cracks in the inlet training was remain tight and without offsets. The bridge appeared to be well aligned and stable, and the concrete was in satisfactory condition. 5. This is a view looking from the spillway ogee weir. The chute walls and floor were stable appearing and well aligned. No signi?cant concrete defects were noted. The concrete patches checked were sound. The rock debris should be removed from the ?ip bucket. Sheet 7 of 9 INSPECTION Or- DAM AND RESERVOIR IN STATUS OI Dam Dam No. 1-50 Dale of Inspection 5 DWR 12:31 (rev. 10:09) Sheet 8 of 9 INSPECTION DAIVI AND RESERVOIR IN CERTIFIED STATUS Name of Darn _A[1te!gpe_ NO- L59. Date of Inspection 9/16/15 DWR 1261 (rt-Eu. 10:09}. fr. STATE OF CALIFORNIA NATURAL RESOURCES AGENCY DEPARTMENT OF WATER RESOURCES DIVISION OF SAFETY OF DAMS INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Darn 139399.? Valley Dam No. 1-50 County Plumes Type of Dam earthfill Type of Spillway Concrete weir and channel Water is 7 feet below .spiIIWay crest and 30 feet dam crest. WS ?4995 feet Weather Primary contacts: David Sarkisian, Vanesa Morones, Kevin Wright, Joe Eades. John Rizzardo, Contacts Made and Jim ScarborOUQh with DWR. Reason for Inspection Annual inspection Important Observations, Recommendations or Actions Taken . The discharge valve was fully cycled during the inspection. . Continue to monitor the seepage areas on the abutments and embankment for changes inflow volume or turbidity. To this end, 08M has developed a reference map of the seepage locations. . Clear and shape the channel from the outlet house to the stream measurement weir to eliminate the high tailwater conditions in that reach of the stream. As previously requested, the nest material within a drain along the lower left spillway well should be removed. Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for continued use. Observations and Comments Min The crest was in good condition, and the asphalt cracks remain sealed. The embankment Da_m appeared to be stable. Vegetation and rodent control were good. The upstream rock protection was sound and well distributed. The slope was in good condition. See photographs and 2. The embankment appeared to be stable and in good condition. See photographs 3 and 4. Di Vegetation and rodent control were good. The rock erosion protection at the toe of the embankment remains in good condition. Sgillway The spillway is shown in photographs 5 and 6. The approach walls and ogee crest were stable and in satisfactory condition. The tight vertical cracks on the approach training walls remain stable. The bridge deck and abutments appeared to be in satisfactory condition. The concrete along the chute floor and walls remains in good condition. No significant offsets, deflections, or concrete deterioration were observed. Patches along the chute floor remain intact- None of the wall drains were flowing. The nest material within a drain along the lower left wall should be removed. The very jointed rock immediately beyond the flip bucket remains stable, but should be inspected following significant releases. elk Inspected by A Photos taken? Yes 3 Date of Inspection 10/3/14 I cc for Book Date of Report 10/30/14 . I ownize1 (Rev. terns) Sheet 8 INSPECTION O. JAM AND RESERVOIR IN STATUS Name of Dam Antelope Valley Dam No. 1-50 Date of Inspection 8/22/13 Observations and Comments Outlet Seepage The seepage patterns were similar to those observed in recent years. has developed a map of the seepage pattern for future reference. See Attachment 1 of this inspection report. The seeps along the lower left groin were clear of brush. As before, standing water was observed along the lower part of the groin, photograph 2. This seepage appeared to be within seasonal limits. Recent water sample testing did not show a relationship between the reservoir water and the seepage water. Water continues to seep along a horizontal zone at mid?level on the right side of the main dam. Water was dripping at the station pipe weir, photograph 10. Conditions appeared to be normal for this location. Small wet areas, with a little standing water, were present on the lower right part of the embankment, about 10 to15?feet above the toe. These areas have been noted in the past and do not have visible flow. No flow was observed from the spillway drains. The weep holes at the outlet training walls were submerged. Past observations of the weep holes indicate reduced flow. This may be due to plugged drains and may be the reason for the continuing seepage observed moving around the training walls, photograph 8. No seepage was observed along the auxiliary dam embankment, groins, or foundation. The toe drain flow was less than 2 and was within the normal range. The latest monitoring report is the 2013 In addition to visual monitoring, the surveillance program includes 15 piezometers and 10 observation wells at the main dam and 3 piezometers and 1 observation Well at the auxiliary dam, seepage monitoring and monument surveys. The main dam piezometer and observation well readings vary within a narrow range and generally remain below the assumed phreatic surface for the 1985 stability analysis. Seepage along the face of the dam has been an issue for many years. The elevated readings at the slope piezometers and wells, P-22, B, and 0W6 seem to reflect this condition. These piezometers should be checked for reliability and the field office should continue regular monitoring of the seepage conditions. Sheet 2 of 8 INSPECTION O. .JAM AND RESERVOIR IN STATUS Name of Dam Antelope Valley Dam No. 1-50 Date of Inspection 8/22/13 Observations and Comments The piezometer and observation well readings at the auxiliary dam remain stable and at, or below, An.? the phreatic surface used for the 196:: stability analysis. Vertical movement at the crest of both embankments has been minimal and appears to have stabilized. Accumulated horizontal movement of the crest monuments has been small and appears to be stabilizing. No significant movement has occurred along the spillway monuments, although monument 43 (10+87) along the right spillway wall has been rising somewhat erratically for a total of 0.5 inches since the first readings were taken in 1971. Based on my field inspection, discussions with staff, and a review of the data, the dam appears to be functioning satisfactorily. Sheet 3 of 8 INSPECTION O. JAM AND RESERVOIR IN CERTII STATUS Name of Dam Antelope Valley Darn No. 1-50 Date of Inspection 3/22/13 I. The spillway inlet structure is visible in this View looking left along the crest of the main dam. The rock on the near side of the spillway is typical of conditions along the main embankment beyond the spillway. ,Jnm 2. The slope of the darn appeared to be stable. The previously observed seepage areas on the slope ranged from clamp to wet, with standing water, but no ?owing water was observed. The usual wet seepage area at the lower left groin is marked by the arrows. Standing water was observed in this area. The light green aspen trees may be a better indicator of the extent of the left groin seepage. Sheet 4 of 8 INSPECTION O. JAM AND RESERVOIR IN CERTII STATUS Name of Dam Antelope Valley Dam No. 1-50 Date of Inspection 8/22/13 3. The crest of the auxiliary dam and the upstream rock wave protection remain in good condition. Note the sealed asphalt cracks. I.I1 4. No signs of instability were observed along the cobble covered slope of the auxiliary dam. DWR1261 Sheet i of i INSPECTION O. JAM AND RESERVOIR IN STATUS Name of Darn Antelope Valley Dam No. 1-50 Date of Inspection 8/22/13 ,y-on :Att'r?rf?a? - Q. . IL 5. The spillway training walls, ogee crest, and bridge remain stable and in satisfactory condition. No signs of Significant concrete deterioration or cracking were Observed. 6. The chute walls and ?oor were stable appearing. No signi?cant concrete deterioration or cracking was observed. The concrete patches remain in good condition. DWR12s1(rev.1oros} Sheet 6 of 8 INSPECTION 0. AND RESERVOIR IN STATUS Name of Dam AnteIOpe Valley 7 Darn No. I50 Date of Inspectinn - .. DWR 12151 (rev INSPECTION O. JAM AND RESERVOIR IN CERTII STATUS Name of Dam ?gtgqung?gy . Darn No. 1?50 Date of lass-Jeanna 3 DWR1261 (rev. 10109) Sheet 8 of 8 STATE OF CALIFORNIA CALIFORNIA NATURAL RESOURCES AGENCY DEPARTMENT OF WATER RESOURCES DIVISION OF SAFETY OF DAMS INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Antelope Valley Dam No. 1-50 County Plumas Type of Dam earthfill Type of Spillway Concrete weir and channel Water is 3.8 feet spillway crest and 26.8 feet dam crest. ws 4998.2 feet Weather Conditions Sunny and mIId Primary contacts: David Sarkisian, Vanesa Morones, Kevin Wright, Joe Eades, Amber Orlof, and Contacts Made Jim Scarborough with DWR. Reason for inspection Annual Inspection Important Observations, Recommendations or Actions Taken . The asphalt cracks along the dam crest have been sealed, as requested. . The discharge valves should be fully cycled for a DSOD engineer during the 2014 operating season. 0 Continue to monitor the seepage areas on the abutments and embankment for changes in flow volume or turbidity. - Remove the small vegetation along the upstream slope of the auxiliary embankment. - Remove the negt within the drain outfall on the lower left spillway chute wall. - will work with DSOD to address the seepage areas on the main dam embankment and the Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for continued use. Observations and Comments Main The crest was in good condition, and the asphalt cracks remain sealed. The embankment Dam appeared to be stable. Vegetation and rodent control were good. The vegetation at the left groin seepage area is starting to grow back, but the area remains visible for inspection purposes. The upstream rock protection was sound and well distributed. The slope was in good condition. See photographs 1 and 2. The long standing seepage areas are discussed in the seepage paragraphs. The embankment appeared to be stable and in good condition. See photograph 3. Vegetation and Dam rodent control were good. The few small trees growing thru the riprap at the upstream left groin should be removed. The rock erosion protection at the toe of the embankment remains in good condition. Spillway The spillway is shown in photographs 4, 5 and 6. The approach walls and ogee crest were stable and in satisfactory condition. The tight vertical cracks on the approach training walls remain stable. The bridge deck and abutments appeared to be in satisfactory condition. The chute floor and walls remain in satisfactory condition. No significant offsets, deflections, or concrete deterioration were observed. Patching along the chute floor remains intact. None of the wall drains were flowing. The nest material within a drain along the lower left wall should be removed. Inspected by WPennington . A Photos taken? Yes No Date of Inspection 8/22/13 if} vi CC for owner/BOOK Date of Report 10/21/13 I Sheet 1 If: 9 0 His INSPECTION L. DAM AND RESERVOIR IN CERT.. IEI STATUS Name of Dam Antelope Valley Dam No. 1-50 Date of Inspection 8/22/13 Observations and Comments Outlet Seepage Instr. II. The very jointed rock immediately beyond me ip bucket remains stable, but should be inspected following significant releases. equipment appeared to be in satisfactory condition. As configured?is a permit required confined space. Both valves should be cycled for a DSOD engineer during the 2014 operating season. Both are operated by the owner on an annual basis. The seepage patterns were similar to those observed over the past several years. The seeps along the lower left groin have been exposed to brush clearing. Standing water was observed along the lower part of the groin. See photograph 8. The seepage appeared to be within the seasonal limits. Water continues to seep along a horizontal zone at mid-level on the right side of the main dam. Water was standing Small wet areas, with a little standing water, were present on the lower right part of the embankment, about 10 to15?feet above the toe. These areas have been noted in the past and do not have visible flow. An example is shown in photograph 9. A recently developed seepage map was developed for future reference and will be provided to DSOD. No flow was observed from the spillway drains. The weep holes at the outlet works training walls were submerged. More recent observations of the weep holes indicate reduced flow. This may be due to plugged drains and may be the reason for the continuing seepage observed along the left outlet training wall. See photograph 10. 08M will have the weep holes flushed to see if the flow along the wall returns to the weep holes. No seepage was observed along the auxiliary dam embankment, groins, or foundation. The toe drain flow was less than 2 and was within the normal range. Continues careful monitoring of the seepage conditions at this dam is recommended. The latest monitoring report is the 2012 The main embankment has 15 piezometers and 10 observation wells, while the auxiliary dam has 3 piezometers and 1 observation well. Seepage monitoring and survey monuments complete the instrumented monitoring program. The main dam piezometer and observation well readings vary within a narrow range. All but two piezometers, P-22 and B, show elevated readings that remain stable. These piezometers Sheet 2 of 9 INSPECTION L. DAM ANI RESERVOIR IN CERT.. STATUS Name of Dam Antelope Valley Dam No. 1-50 Date of Inspection 8/22/13 Observations and Comments should be checked for reliability. The piezometer and observation well readings at the auxiliary dam remain stable and?below the phreatic surface used for the stability analysis. Vertical movement at the crest of both embankments has been minimal and appears to have stabilized. Accumulated horizontal movement of the crest monuments has been small and appears to be stabilizing. No significant movement has occurred along the spillway monuments. The phreatic surface within the main dam appears to be satisfactory. However, will work with DSOD to address the seepage areas on the slope. The current suite of instruments is adequate in the interim. Sheet 3 of 9 INSPECTION DAM AND RESERVOIR IN STATUS Name of Dam Antelope Valley Dam No. 1~50 Date of Inspection 8122/ 3 ?we 3 I. This View lookin northwest alon the main embankment shows the spillway alignment in the background, dotted arrow, Asphalt sealing along the crest road is visible at right. 2. This View is looking along the main dam from the left abutment. The heavy rock wave protection remains soand and well distributed. The spillway buoy line is visible in the background. DWR1261 (rev.10f09) Sheet 4 of 9 INSPECTION Lo. DAM AND RESERVOIR IN CERTI. STATUS Name of Darn Antelope Valley Darn No. 1-50 Date of Inspection 8122/ 1 3 3. This view of the auxiliary dam was taken from a point above the right abutment. Both sides of the embankment remain in satisfactory condition. The heavy rock wave protection remains sound and well distributed. 4. The spillway ogee crest remains in satisfactory condition. No signs ofsettlement or concrete deterioration were observed. DWR1261 (rev. 10:09) Sheet of i INSPECTION L. DAM AND RESERVOIR IN STATUS Name of Dam Antelope Valley Dam No. 1-50 Date of Inspection 3122/1 3 5. The Spillway chute and ?ip bucket are shown. The walls and ?oor appeared to be stable and in satisfactory condition. The bird nest in one of the lower left wall drains should be removed, as previously requested. Sheet 6 of 9 INSPECTION L. DAM AND RESERVOIR IN .ED STATUS Name of Dam Antelope Valley Dam No. 1~50 Date of Inspection 8/22/13 6. The rock beyond the end of the spillway ?ip bucket is shown. This severelyjointed rock Should be observed following prolonged heavy spills. As in the past, a small amount of seepage was observed at the toe of this steep rook ledge. DWR1261(rev.10t09) Sheet 7 of 9 INSPECTION L. DAM AND RESERVOIR IN CERT.. .ED STATUS Name of Dam Antelope Valley __Dam No_ 1-50 Date of Inspection 3/22/13 8. Thu lowcr lcl?l abutment. seepage area at the main dam is shown. This arca should be nminlained free of to allow visual monitoring of the seepagc. DWR 1251 (rev. 10:09) Sheei 8 of 9 INSPECTION L- DAM AND RESERVOIR IN .ED STATUS Name of Dam Antelope Valley Dam No, Date of lnspeetien__ 8/22/13 9. A previously observed wet area on the lower right side ofthe main embankment is shown. Flew was not evident. DWR1281 (rev. 10109) Sheet _9 of 9 3 6 /6 STATE OF CALIFORNIA CALIFORNIA NATURAL RESOURCES AGENCY DEPARTMENT OF WATER RESOURCES DIVISION OF SAFETY OF DAMS INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Antelope Valley Dam No. 1-50 County Plumas Type of Dam earthfill Type of Spillway Concrete weir and channel Water is 6 feet below spillway crest and 29 feet dam crest. ws ~4996 Weather Conditions Sunny and mild Primary contacts: David Sarkisian, Vanesa Morones, Kevin Wright, and Jim Scarborough with Contacts Made DWR. DSRB members: Bill Rettberg, Lelio Mejia, Keith Kelson Reason for inspection Annual inspection Important Observations, Recommendations or Actions Taken 9 The centerline of the dam crest was surveyed and found to be above the nominal design elevation. The piezometer extensions at the toe of the dam have been repaired as requested. 9 The as halt cracks alon the dam crest have been sealed as requested. been cycled through full travel for DSOD within the last wo seasons. . Remove the small vegetation along the upstream slope of the auxiliary embankment. - The instrumented and visual monitoring program is currently under review by and may be revised following the PFMA to be conducted in November 2012. Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for continued use. Observations and Comments The embankment appeared to be stable. Photograph 1 illustrates the asphalt crack sealing and li?m the overall condition of the crest along both embankments. Vegetation and rodent control were good. The left groin seepage area remains clear of vegetation. The upstream rock protection was sound and well distributed. See photograph 2. The slope was in good condition. See photographs 3 and 4. Au; The embankment appeared to be stable and in good condition. See photograph 5. Vegetation and Dam rodent control were good. The few small trees growing thru the riprap at the upstream left groin should be removed. A crew was placing rock erosion protection in the eroded channel at the toe of the embankment. See photograph 5. Spillway The approach walls and ogee crest were stable and in satisfactory condition. Tight cracks have propagated downward from the chain link post holes along both approach walls. See photograph 6, for example. The joint sealing at the center of the ogee crest should continue to the first transverse joint in the chute floor to control infiltration below the slab. See photograph 7. The chute floor and walls remain in satisfactory condition. No significant offsets, deflections, or concrete deterioration were observed. Patching along the chute floor remains intact. The flip bucket drain should be checked for blockage. None of the wall drains were flowing. The nest material within a drain outfall along the lower left wall should be removed. The very jointed rock immediately beyond the flip bucket remains stable. V6 Inspected by WPennington [0 Photos taken? Yes N0 Date of Inspection 926-1 2 I cc for Owner/Book Date of Report 10/25/12 Iv DWR 1261 (Rev. 10/09) Sheet 1 of 12 I $1.1th INSPECTION (au- DAM AND RESERVOIR IN IED STATUS Name of Dam Antelope Valley Dam No. 1-50 Date of Inspection 9/26/12 Observations and Comments Seepage The bridge deck and abutments appeared to be in satisfactory condition. An updated hydrology study has been completed. DOE is in the process of routing the inflow throu the reservoir. equipment appeared to be in satisfactory condition. As configured, is a ermit required confined space. The required safety rotocol does not lend itself tishould the need arise. As previously requested, ?should be configured to remove the permit required confined space designation. valve and the gate were fully cycled for a DSOD engineer within the last two years. Both are typically used on a yearly basis. The seepage patterns were mostly similar to those observed during recent inspections. A possible exception was a small wet area observed about 15?feet above the toe of the main embankment. This area should be observed during routine inspections to see if it enlarges, or starts to flow. See photograph 9. Water continues to seep along a zone at. mid-level on the ri ht side of the main dam. See photograph 10. Seepage water was dripping over the weir. Field staff should continue to monitor this area for changes in flow volume and turbidity. Consideration should be given to assessing the source of water by using chemical analysis techniques. The seeps along the lower left groin have been exposed to a large extent bybrush clearing. Standing water was observed at the lower left toe. See photograph 10. The seepage appeared to be within historical and seasonal limits. No flow was observed from the spillway drains. The weep holes at the outlet works headwalls were submerged by the discharge. Seepage was observed along the transverse portion of the left wall. See photograph 9. No seepage was observed along the auxiliary dam embankment, groins, or foundation. The toe drain flows were within the normal range. See photograph 11. 08M has chosen the FERC format to record and evaluate surveillance data. The latest report is the 2011 The main embankment has 15 piezometers and 10 observation wells, while the auxiliary dam has 3 piezometers and 1 observation well. Seepage monitoring and survey monuments complete the instrumented monitoring program. A typical piezometer and monument installation is shown in photograph 12. The-piezometers readings remain below the phreatic surface used for the last stability Sheet 2 of 12 INSPECTION (Jr DAM ANI RESERVOIR IN IED STATUS Name of Dam Antelope Valley Dam No. 1?50 Date of Inspection 9/26/12 Observations and Comments analysis. The phreatic surface in the shell and foundation remains normal for this dam, with the notable exception of piezometers P- 22 and P- 21 B, which continue to show elevated readings These piezometers should be checked for reliability Vertical movement at the crest of both embankments has been minimal and appears to have stabilized. Accumulated horizontal movement of the crest monuments has been small and appears to be stabilizing. No significant movement has occurred along the spillway monuments. The instrumented and visual monitoring program is currently under review by and may be revised following the PFMA to be conducted in November 2012. The current Suite of instruments is adequate in the interim. Based on my field inspection and a review of the instrument data, the dam appears to be functioning satisfactorily. Sheet 3 of 12 DAM AND RESERVOIR IN IED STATUS Name of Darn Antelope Valley Dam No. 1-50 Date of Inspection 9/2511 2 1. This View of the auxiliary dam crest is representative of the crest conditions along both embankments. Note the quality of the crack sealing. 2. The rock along the upstream slope was stable and sound. The spillway buoy line is visible in the background. Antelope Valley Dam, No. 1~50 Plumas County 9/26/ 12 DWR 1261 (rev. 10(09) Sheet 4 0f 12 INSPECTION Cn- DAM AND RESERVOIR IN CERTI. IED STATUS Name of Darn Antelope Valley Dam No. 1-50 Date of Inspection 9/25/12 3. The stable appearing slope of the main dams remains in satisfactory condition. No rodent activity or objectionable vegetation was observed. Antelope Valley Dam, No. 1-50 Plumas County WPennington 9/26/12 DWR 1261 (rev. 10r'09) Sheet 5 Of 12 INSPECTION C). DAM AND RESERVOIR IN IED STATUS Name of Dam Antelope Valley Dam No. 1-50 Date of Inspection 9/25/12 - :shiIi, at. ?315-4? th?Mh f? I 4. This View of the main el?bankment?and the Spillway adjacent to the right abutment. 4'7 . Antelope Valley Dam, No. 1-50 Plumas County WPermingtOIl 9/26/ 12 DWR1261 (rev.10f09) Sheet i 01? Ln- DAM AND RESERVOIR IN IED STATUS Name of Dam Antelope Valley Darn No. 1-50 Date of Inspection 9/2611 2 5. This View of the auxiliary dam shows the good condition of the embankment and a crew placing rock in an erosion channel at the toe. Antelope Valley Dam, No. 1-50 Plumes County WPennington 9/26/ 12 Sheet 7 of 12 INSPECTION 0r DAM AND RESERVOIR IN STATUS Name of Dam Antelope Valley Darn No. 1~50 Date of Inspection 9/26/12 6. Both spillway approach walls were stable and in good condition. This picture shows (arrow) one of the typical cracks that have propagated downward from the fence post holes. These cracks are tight and do not pose a threat to the structure. Antelope Valley Dam, No. 1-50 Plumas County WPennington 9/26/ 12 owmzet (rev.10f09) Sheet 8 of 12 INSPECTION Cn- DAM AND RESERVOIR IN STATUS Name of Dam Antelope Valley Dam No. 1-50 Date of Inspection 9/25/12 7. The looking upstream along the spillway chute. The bridge and upper chute were in good condition. The joint at the arrow should be sealed down to the ?rst transverse joint along the chute ?oor. Antelope Valley Darn, No. 1-50 Plumas County WPennington 9/26/12 DWR1261 (rev. 10f09) Sheet 9 of 12 INSPECTION b. DAM AND RESERVOIR IN .ED STATUS Name of Dam ?nIelqpe Valley Dam No. Date of Inspectiml 9126/1 2 .r'M'Ilcalopc Dam. No. 1?50 Plum-as \h?"l"enni11g1011 '2 DWR 1261 (rev. 10x09; Sheet of INSPECTION Ch DAM AND RESERVOIR IN .ED STATUS Name of Dam Antelope Valley Dam No. 1-50 Date of Inspection 9/26/12 10. This View shows the long standing mid-level see a area at side of the main embankment.? The arrow shows the lateral extent of the seepage. Also shown is the cleared lower left groin seepage area. The seepage area extends into the stand of deciduous trees at the top of the picture. Antelope Valley Darn, No. 1-50 Plumes County WPennington 9/26/12 DWR1251(rev.1omg) Sheet 11 of 12 INSPECTION D. DAM AND RESERVOIR IN CENTI. .ED STATUS- Name of Dam p53 Darn MD. 1:50 Date ch Inspection 9/26/12 Valley Dam, No. 1?50 County WPunningu'm WHEN 2 DWR 12651 (rev. 10309,}