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 Peters Dam No. 33?7 County Marin Type 01? Dam ERTH Type of Spillway Concrete weir and chute Water is 2.9 feet above the spillway crest and 11.9 feet below the dam crest. Weather Conditions Overcast with light rain Contacts Made Lucy Croy, Trinity Leonard, Carl Sanders, and Ronnie Chasteen during the inspection Reason for inspection Periodic Evaluation Important Observations, Recommendations or Actions Taken Overall care and maintenance of the dam and appurtenances is excellent. A large redwood log that has drifted into and was caught on the right side of the concrete Spillway control weir requires removal. Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for continued use. Observations and Comments Dam The visible portion of the upstream face, crest, face, and abutments are in satisfactory condition with no indication of surficial distress or instability. The large boulder rock riprap upstream face protection remains in good condition. Vegetation control is excellent, and the crest, groins, and face of the embankment are covered with ankle tall grass and other low ground cover that protect against erosion without hindering inspection and monitoring for seepage and other defects. Similar to recent past inspections, rodent control remains satisfactory and few to no indications of rodent activity were observed. The roadway cut and hillside above the outlet tower shows no obvious signs of renewed movement. Past sliding at this location during a winter storm has reportedly caused damage to the outlet valve controls. Spillway There was approximately 2.9 feet of flow over the spillway control weir. The approach and exit channel were clear and unobstructed; a large redwood log that has drifted into and was caught on the right side of the concrete spillway control weir requires removal. The concrete walls and invert could not be inspected due to flow within the spillway, but they were inspected during the previous inspection on 5 April 2016 and were found to be in good condition at that time. The original spillway, now used as a discharge chute for the 60? diameter upper level outlet, remains in satisfactory condition. The current design storm, prepared in 1981, is for a 170,000 year return period producing 19,900 ~94? sq mi) from the 22.1 square mile drainage area. The spillway capacity is ~20, 900 which Is greater than the peak inflow. Total freeboard' IS 15 feet and the residual freeboard for the design storm is 2. 5 feet. Freeboard Is satisfactory. .. s. r; 2m Inspected by J. Lowe/f taken? Yes N0 Date 7 February 2017 cc for Owner/Book Date of Report 13 February 2017 LI I 7 we 1r DWR1261 (Rev. 10:09) Sheet 1 of 5 Name of Dam INSPECTION UF DAM AND RESERVOIR IN CERTIFIED STATUS 33?7 Peters Dam No. 7 February 2017 Date of Inspection Observations and Comments Outlet Seepage DWR 1261 (rev. 10109) Upstream control for the fully encased normally pressurized outlet is provided by six 30?inch gate valves arrayed along a 48?inch diameter inclined inlet tower at elevations of 345.0?, 333.5?, 320.0?, 295.0?, 260.0?, and 215.0', and by a 36~inch butterfly valve at elevation 379.5?. control for the inclined tower is provided by a 36-inch diameter butterfly valve near the left toe of the embankment. A separate high?level outlet controlled on both the upstream and sides by two 60?inch diameter butterfly valves provides additional outlet control. None of the outlet controls were cycled during this inspection, but all outlet controls were partially cycled during the 5 April 2016 inspection and were found to be in good operating condition at that time. All outlet controls were fully cycled and found to be in satisfactory operating condition during the February 25, 2015 periodic inspection. Mr. Anaya of the MMWD also performed a full head test of the outlet system on January 26, 2016?, this is the first time the outlet has been tested under full reservoir head in over fifteen years. Rainfall prevented evaluation for minor seepage. No evidence of significant seepage was observed along the face, abutments, or groins. Seepage from the single toe drain was estimated to be approximately 60 at the 90?degree V~notch weir. Seepage over both the V?notch weir and the right and left collar drains was clear and within historic volumes. Instrumentation consists of: a Sixteen (16) survey monuments distributed along the crest and along a row near the mid elevation of the embankment, are designed to measure movement following significant seismic events. a Seventeen (17) piezometers distributed along the crest, along a row near the mid elevation of the embankment, and on the embankment above and along the toe. Piezometers are designed to measure pore pressures within the embankment and along the abutments. a One (1) seepage measurement weir located near the valve house adjacent to the outfall of the fish?water release weir. Design elevations for the piezometers are: Comments Piezometer Depth to Bottom Design Tip Number of Piezometer Elevation 35.5 376.3 Clogged circa March 1999, reopened Oct. 2001 P-1A 45.0 370.7 . P2 63.3 344.8 - 68.1 340.5 9?4 93.9 345?9 Replaced by in 1986. Piezometer was replaced by P-4A in 1986. 88.2 322.1 P-6 34.1 382.4 P-6A Critical elevation 280? 57.6 266.1 Sheet 2 of 5 INSPECTION uF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Peters Darn No. 33-7 Date of Inspection 7 February 2017 Observations and Comments 9?6 441-676 246:6 Abandoned and replaced by in 1986 P-8A Critical elevation 236' P-9 50.0 268.3 P-10 74.2 186.6 Critical elevation 229, monitors pressure at toe P-10A 91.0 183.4 Critical elevation 230, monitors pressure at toe P-1OB 70.0 179.8 Critical elevation 228, monitors pressure at toe P-11 56.5 177.3 Critical elevation 220 P-11A 66.4 177.8 Critical elevation 225 P-11B 39.0 172.2 Critical elevation 205 The latest instrumentation data was received from the owner on December 16, 2015, and no new data has been received since that time. The last instrumentation review is presented in the 5 April 2016 inspection report, and is not repeated here; I direct the reader to the earlier report for a detailed explanation of the instrumentation monitoring the dam, and the performance of the dam as reflected in the 16 December 2015 submittal. The conclusion of the April 2016 review was that, ?Based on the data submitted the dam appears to be performing satisfactorily, and no additional instrumentation is believed necessary at this timeThe upstream face as viewed from the left abutment. The large boulder rock riprap upstream face protection remains in good condition. DWR1261 (rev. 10mg) Sheet 0? i INSPECTION uF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Peters Dam No. 33?7 Date of Inspection 7 February 2017 Looking across the face of the embankment towards the left groin, above, and another look at the left groin and toe, below. As evident by the photographs, vegetation control is excellent. DWR1261 (rev. 10109) Sheet 4 of 5 INSPECTION UF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Darn Peters Dam No. 33?7 Date of Inspection 7 February 2017 .:large redwood log that has drifted into and was caught on the right side of the concrete spillway control weir requires removal, above. The photograph below shows flow within the concrete spillway channel entering the unlined spillway exit channel. Sheet 5 of 5 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 Peters Dam No. 33?7 County Marin Type of Dam ERTH Type of Spillway Concrete weir and chute Water is 0.5 feet below the spillway crest and 15.5 feet below the darn crest. Weather Conditions Clear and mild Contacts Made Alex Anaya and Ronnie Chasteen during the inspection Reason for Inspection Periodic Evaluation Important Observations. Recommendations or Actions Taken Overall care and maintenance of the dam and appurtenances has improved significantly over the past three years. Mr. Anaya has addressed all safety and maintenance concerns expeditiously and comprehensively, and none other than normally scheduled maintenance is required at this time. The following are some of the issues resolved by Mr. Anaya since the previous inspection on February 25, 2015: - Vegetation control along the face has improved significantly, and is now excellent. Tall and dense bushes and emerging trees throughout the embankment and groins have been cleared to open these important areas to improved monitoring for seepage and other defects. I called Mr. Carl Sanders to thank him for the excellent work he and his crew performed in correcting all vegetation control deficiencies. - Small willow trees and woody bushes that had taken root within construction joints along the upper level outlet outfall chute have been removed to prevent damage to the concrete chute invert and sidewalls. . On January 26, 2016, the outlet control was run under full head for the first time in over fifteen years. Mr. Anaya's outlet valve operation plan and documentation of the full head outlet operation is attached to this report. Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for continued use. Observations and Comments Dam The visible portion of the upstream face, crest, face, and abutments are in satisfactory condition with no indication of surficial distress or instability. The large boulder rock riprap upstream face protection remains in good condition. Vegetation control along the face has improved significantly, and is now excellent. Tall and dense bushes and emerging trees throughout the embankment and groins have been cleared to open these important areas to improved monitoring for seepage and other defects. I called Mr. Carl Sanders to thank him for the excellent work he and his crew performed in correcting all vegetation control deficiencies. Similar to recent past inspections, rodent control remains satisfactory and few to no indications of rodent activity were observed. The roadway cut and hillside above the outlet tower shows no obvious signs of renewed movement, Past sliding at this location during a winter storm has reportedly caused damage to the outlet val Inspected by J. Lowe' - f?j?v?rdwt Photos taken? Yes No Date of Inspection 5 cc for Owner/Book Date of Report 6 April 2016 DWR 1261 (Rev. torus) Sheet a iI7 INSPECTION DAM AND RESERVOIR IN CER STATUS Name of Dam Peters Dam No. 33-7 Date of Inspection 5 April 2016 Observations and Comments SQiIIway Outlet Seepage DWR 1261 controls. The approach, control section, and exit channel were clear and unobstructed. The concrete walls and floor remain in good condition, with no significant indications of structural or physical deterioration. The original spillway, now used as a discharge chute for the 60? diameter upper level outlet, is in satisfactory condition. Small willow trees and woody bushes that had taken root within construction joints along the upper level outlet outfall chute have been cleared to prevent damage to the concrete chute invert and sidewalls. Total freeboard is 15 feet and the residual freeboard for the design storm is 2.5 feet. Freeboard is satisfactory. Upstream control for the fully encased normally pressurized outlet is provided by six 30~inch gate valves arrayed along a 48-inch diameter inclined inlet tower at elevations of 345.0?, 333.5?, 320.0?, 295.0?, 260.0?, and 215.0?, and by a 36-inch butterfly valve at elevation 379.5?. control for the inclined tower is provided by a 36?inch diameter butterfly valve near the left toe of the embankment. A separate high-level outlet controlled on both the upstream and sides by two 60-inch diameter butterfly valves provides additional outlet control. All of the outlet controls were partially cycled during this inspection, and all were found to be in good operating order. All outlet controls were fully cycled and found to be in satisfactory operating condition during the February 25, 2015 periodic inspection. Mr. Anaya also performed a full head test ofthe outlet system on January 26, 2016', this is the first time the outlet has been tested under full head in over fifteen years. Mr. Anaya?s outlet valve operation plan and documentation of the full head outlet operation is attached to this report. No evidence of seepage was observed along the face, abutments, or groins. Seepage from the single toe drain was estimated to be approximately 40 at the SID-degree V?notch weir. There was no seepage from the 60" diameter upper level outlet discharge, and seepage from both the left and right collar drains for the upper level outlet discharge was only a slight trickle. Seepage over both the V-notch weir and the right and left collar drains was clear and within historic volumes. Instrumentation consists of: Sixteen (16) survey monuments distributed along the crest and along a row near the mid elevation of the embankment, are designed to measure movement following significant seismic events. a Seventeen (17) piezometers distributed along the crest, along a row near the mid elevation of the embankment, and on the embankment above and along the toe. Piezometers are designed to measure pore pressures within the embankment and along the abutments. a One (1) seepage measurement weir located near the valve house adjacent to the outfall of the fish~water release weir. (rev. 10:09) Sheet 2 of 5 ENSRECTEON DAM AND RESERVOIR IN STATUS Name of Dam Peters Dam No. 33?7 Date of Inspection 5 April 2016 Observations and Comments Design elevations for the pie'zometers are: Piezometer Depth to Bottom Design Tip Comments Number of Piezometer Elevation P-1 35.5 376.3 Clogged circa March 1999, reopened Oct. 2001 P-1A 45.0 370.7 P-2 63.3 344.8 68.1 340.5 9?4 9379 345?9 Replaced by in 1986. P-4A Piezometer P-4 was replaced by P-4A in 1986. P-5 88.2 322.1 P-6 34.1 382.4 Critical elevation 280? 57.6 266.1 . 9-8 41?1676 24% Abandoned and replaced by P-8A in 1986 P-8A Critical elevation 236? P-9 50.0 268.3 P-10 74.2 186.6 Critical elevation 229, monitors pressure at toe 91.0 183.4 Critical elevation 230, monitors pressure at toe P-10B 70.0 179.8 Critical elevation 228, monitors pressure at toe P-11 56.5 177.3 Critical elevation 220 P-11A 66.4 177.8 Critical elevation 225 39.0 172.2 Critical elevation 205 The latest instrumentation data was received from the owner on December 16, 2015; survey data covers the reporting period between September 1982 and November 2015. Survey data for the period from September 1982 through January 2015 was reviewed. Settiement, while continuing, is insignificant. The maximum cumulative settlement was reported as 0178 feet (2.1 inches) at monument M8 in September of 2014. Aiignment deviation is also insignificant. Recorded movements are within 0.13 feet (1.6 inches) with a roughly equal distribution of upstream and movement. Based on the distribution, and thesmall reported dispiacements, it appears that the results reflect primarily instrument and reading error rather than actual displacement, and that the dam remains stable with regard to alignment. The seepage measurement weir adjacent to the outfail of the fish?water reiease weir is designed to measure seepage from the toe drain. Measured seepage rates have varied from 0.0 to as high as 1,200 in February of 1982, reportedly the result of a combination of seepage and surface runoff following a period of intense rainfall. Since April of 1983 MMWD has diverted surface drainage away from the weir pond and the maximum reported reading since that time has been 420 in February of 1986. For the January 2006 through July 2015 data period reviewed, the maximum reported seepage was just over 300 gpm?in January of 2015, with average annual flow rates less than 75 gpm. Piezometer water surface elevations for the January 2001 through January 2011 period reviewed are stable with no significant increasing or decreasing trends, and levels remain below ?phreatic surface number which has been determined to be the maximum surface (critical eievation) for adequate stability as shown in the DSOD memorandum from V.H. Persson to J. E. Ley dated 27 July 1983. DWR1261(rev.10l09) Sheet 3 of 5 DAM AND RESERVOIR IN CER TIED STATUS Name of Dam Peters Dam No. 33-7 Date of Inspection 5 April 2016 Observations and Comments In their December 16, 2015 instrumentation data submittal letter the owner reports, ?The Peters Dam (Kent Lake) piezometers and weir ?ows are consistent with historic readings. Peters Dam (Kent Lake) is trending toward stabilization: Settlement of -0. 18 ft (maximum) and alignment of -O. 13 feet direction; maximum)? Based on the data submitted the darn appears to be performing satisfactorily, and no additional instrumentation is believed necessary at this time. 1" anThe upstream face as viewed from the right abutment. The large boulder rock riprap upstream face protection remains in good condition. The spillway entrance through the left abutment is circled. DWR1261(rev.10i09) Sheet 4 of 5 INSPECTION DAM AND RESERVOIR IN CER STATUS Name of Dam Peters Dam No. 33-7 Date of Inspection 5 April 2016 . .nkThe face as viewed from the right abutment, above, and from the left abutment, below. As is evident from the photographs, vegetation control is now excellent. DWR 1261 (rev. 10109) Sheet 5 Of 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 Peters Dam No. 33-7 County Marin Type of Dam ERTH Type of Spillway Concrete Weir and chute Water is 2 feet below the spillway crest and 17 feet below the dam crest. Weather Conditions Clear and mild Contacts Made Alex Anaya and Ronnie Chasteen during the inspection Reason for Inspection Periodic outlet valve cycling and evaluation Important Observations. Recommendations or Actions Taken This inspection was limited to observation of the cycling of, and evaluation of, the upstream and outlet controls. There have been no substantive changes in the condition of the dam and appurtenances since the previous annual inspection performed on October 30, 2014. Observations, recommendations, or actions concerning the embankment and its appurtenances are presented in the October 30, 2014 inspection report, the contents of which are not repeated here. Both outlet control butterfly valves experienced severe cavitation during partial cycling under full reservoir head. I asked Mr. Anaya to develop a procedure to permit safely operating all valves under full reservoir head, and for the procedure to be demonstrated during the next valve cycling inspection. An alternative long-term solution would be to replace the most valve with a cone valve designed for partial open operation under high pressure head. Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for continued use. Observations and Comments Outlet Upstream control for the fully encased normally pressurized lower-level outlet is provided by six 30- inch gate valves arrayed along a 48-inch diameter inclined outlet intake at elevations of 345.0?, 333.5?, 320.0?, 295.0?, 260.0?, and 215.0?, and by a single 36-inch butterfly valve at elevation 379.5'. control for the inclined tower is provided by a pair of 36-inch diameter butterfly valves arrayed in series near the left toe of the embankment. A separate high-level outlet controlled on both the upstream and sides by two 60-inch diameter butterfly valves provides additional drawdown capacity. All upstream and controls were fully cycled. The upstream 60-inch butterfly valve requires 552 turns to fully open or close; the 60-inch butterfly valve requires 582 turns to fully open or close. The six upstream control 30-inch gate valves require 319 turns to open or close, and the pair of 36 inch control butterfly valves require 39 turns to open or close. Both high-level outlet 60-inch butterfly valves, the 36-inch upstream outlet control butterfly valve, and both lower-level controls, were cycled with the aid of a handheld E.H. Wachs P-2 hydraulic power head which rotates at between 0-12 RPM, and applies a maximum torque of 800 ft- lbs. Rotational speed during the valve cycling at Peters Dam averaged roughly 4.5 RPM. The remaining upstream controls were cycled by hand. Both outlet control butterfly valves experienced severe cavitation during partial cy Ing Inspected by J. 7 Photos taken? Yes No Date of Inspection 25 2015 aim cc for Owner/Book Date of Report 27 February 2015 {5 DWR 1261 (Rev. 10(09) Sheectbl DAM AND RESERVOIR IN CEF STATUS Name of Dam Peters Dam No. 33-7 Date of Inspection 25 February 2015 Observations and Comments under full reservoir head. The upstream of the two butterfly valves is designated the of the two valves is designated 7250F. To prevent damage to the valves we terminated the full head portion of the test when the valves were open less than 50 percent. Both valves were fully cycled with the alternate valve fully closed. I asked Mr. Anaya to develop a procedure to permit safely operating all valves under full reservoir head, and for the procedure to be demonstrated during the next valve cycling inspection. An alternative long-term solution would be to replace the most valve with a cone valve designed for partial open operation under high pressure head. Cycling the upper?level 60-inch butterfly valves, above and below. Opening and closing both valves required over 2,260 turns of the handwheel, which tookjust under four hours to completeSheet 2 of 3 DAM AND RESERVOIR IN CEF STATUS Name of Dam Peters Darn No. 33-7 Date of Inspection 25 February 2015 Cycling the lower-level outlet controls, above and below. In the photograph below, the valve designated 7250A is being cycled. The blue stake in the foreground marks the location of the most valve, designated 7250F. DWR 1261 (rev. 10:09) Sheet 3 0f 3 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 Peters (Kent) Darn No. 33-7 County Marin Type of Darn Earth Type of Spillway Concrete weir and chute Water is 24 feet below spillway crest and 39 feet below dam crest. Weather Conditions Sunny and cold Contacts Made Carl Gowan before, Alex Anaya, Carl Sanders, Ben Bauer during the inspection Reason for Inspection Periodic Maintenance Inspection Important Observations, Recommendations or Actions Taken Circled vegetation along the spillway walls needs to be removed to prevent potential damage to the spillway concrete. See Photo 1. There are no prior outstanding administrative requirements. The total class weight of 26 appears satisfactory. Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for continued use. Observations and Comments Dam The visible portion of the upstream face, crest, face, and abutments are in satisfactory condition with no indication of surficial distress or instability. The upstream darn face is armored with large riprap. Vegetation control remains satisfactory and the embankment remains covered in ankle tall grass and other low ground cover that protects against erosion without hindering inspection and monitoring for seepage and other defects. No woody vegetation was observed on the dam or along the groins. Similar to recent past inspections, rodent control remains satisfactory and few to no indications of rodent activity were observed. Spillway The approach, control section, and exit channel were clear and unobstructed. The concrete walls and floor remain in good condition and appeared structurally sound. No evidence of excessive deterioration of the concrete was observed. The owner should remove vegetation, near the chute, as circled in Photo 1, to prevent potential damage to the spillway concrete. The original spillway, now used as a discharge chute for the 60? diameter upper level outlet, remains generally in satisfactory condition. The current design storm, prepared in 1981, is for a 170,000?year return period producing 19,900 sq mi) from the drainage area. The spillway capacity is ~20,900 which is greater than the peak inflow. Total freeboard is 15 feet and the residual freeboard for the design storm is 2.5 feet. The freeboards are satisfactory. Inspected by %h i? .- (- Photos taken? Yes No Date of Inspection 40/30/2014,, L1 cc for Owner/Book Date of Report I Sheet 1 0f INSPECTION DAM AND RESERVOIR IN .. STATUS Name of Dam Peters (Kent) Dam No. 33-7 Date of inspection 10/30/2014 Observations and Comments Outlet Seepage Upstream control for the fully encased normally pressurized primary outlet is provided by six 30~inch gate valves arrayed along a 48-inch diameter inclined outlet intake at elevations of 345.0?, 333.5?, 320.0?, 295.0?, 260.0?, and 215.0?, and by a single 36-inch butterfly valve at elevation 379.5?. control for the outlet line is provided by a 36?inch diameter butterfly valve near the left toe of the embankment. A separate high?ievei outlet, controlled on both the upstream and sides by two 60-inch diameter butterfly valves, provides additional drawdown capacity. None of the controls were cycled during the inspection. All upstream and controls were fully cycled except for the 36-inch control during the previous inspection ofAugust 14? 16, 2013 inspection. This August 14?16, 2013 inspection was scheduled exclusively to witness the operation of outlet controls and each control gate was cycled and found to be in Operable condition. The 36?inch control could not be cycled during this inspection because the owner was performing some repair work on the outlet line, of the 36?inch butterfly valve. The owner will be asked to cycle this valve during the next inspection. No evidence of seepage was observed along the dam face, abutments, or groins except for the monitored seepage through the toe drain. Seepage flow at the v-notch weir was estimated to be 20 at the time, this is acceptable. There was no obvious leakage from the 60? diameter upper level outlet discharge pipe. Instrumentation consists of sixteen (16) survey monuments, seventeen (17) piezometers, and one (1) seepage measurement weir The most recent instrumentation report was transmitted on September 24, 2014 and it consists of seepage, piezometer, and monument survey data and plots. The report also includes a brief evaluation (one liner) of the data. Seepage: Review of the long term seepage plot (2005-2014) shows that the seepage flow is generally responding to reservoir water elevation and the rainfall. During the current reporting period of July 2013 to June 2014, seepage varied between 20 to 125 and it remained below the historical limits. Piezometers: Piezometer plots for all 17 piezometers do not show any adverse trends. During the current reporting period, piezometer levels are consistent and within the historical limits. - Monuments Survey: Monuments are surveyed bi-annually. The most recent survey was performed in September 2014 and the data is presented in a tabular and graphical format (table and a 32?year plot, 1982-2014). Review of the plots show that settlement is progressiveiy decreasing and the embankment is trending towards stabilization. Simiiarly, review of alignment plots does not show any noticeable movement in the upstream or direction except for monument M6. This monument is located on the dam crest in the left half of the dam and within the reporting period, shows about 0.05 ft movement in the direction. This may be either a reading error or the monument itself is disturbed, because other monuments near M6 do not show any noticeable movement. The owner will be asked to investigate should the movement continue during the next survey. DWR1261(rev.10f09) Sheet 2 of 4 INSPECTION DAM AND RESERVOIR IN .ED STATUS Name of Dam Peters (Kent) Darn No. 33-7 Date of Inspection 10/30/2014 1. View of the spillway channel looking Circled vegetation along spillWay walls needs to be removed. 2. A View of the upstream darn face as seen from the right end. DWR1261 (rev. 10/09) Sheet 3 of 4 INSPECTION IL DAM AND RESERVOIR IN .- .ED STATUS Name of Dam Peters (Kent) Dam No. 33-7 Date of Inspection 10/30/2014 3. A partial View of the dam face as seen from the right groin. As seen here, the majority of the embankment is well covered with ankle high grass and free of any woody vegetation. Sheet 4 of 4 STATE OF CALIFORNIA NATURAL RESOURCES AGENCY DEPARTMENT OF WATER RESOURCES OF SAFETY OF DAMS INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Peters Dam NO. 33-7 County Marin Type of Dam ERTH Type of Spiilway Concrete weir and chute Water is 12 feet below the spillway crest and 27 feet below the dam crest. Weather Conditions Clear and mild Contacts Made Frank Figone during the inspection Reason for Inspection Periodic outlet valve cycling and evaluation Important Observations. Recommendations or Actions Taken This inspection was performed to inspect and evaluate the condition Of the outlet controls. There have been no substantive Changes in the condition of the dam and appurtenances since the previous annual inspection performed on April 24, 2013. Observations, recommendations, or actions taken during the April 2013 inspection remain as presented in the April report, the details Of which are not repeated here. Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for continued use. Observations and Comments Outlet Upstream control for the fully encased normally pressurized primary outlet is provided by six 30?inch gate valves arrayed along a 48-inch diameter inclined outlet intake at elevations of 345.0?, 333.5?, 320.0', 295.0?, 260.0?, and 215.0', and by a single 36-inch butterfly valve at elevation 379.5?. control for the inclined tower is provided by a 36-inch diameter butterfiy valve near the left toe of the embankment. A separate high-level outlet controlled on both the upstream and sides by two 60-inch diameter butterfly valves provides additional drawdown capacity. Before this inspection the outlet controls were last cycled in the presence Of DSOD staff during the July 2009 periodic inspection, at which time all of the valves were found to be in good operating condition. All upstream and controls were fully cycled except for the 36-inch control at the toe ofthe dam, which is scheduled to be cycled later in the season. All valves were cycled with the aid of a handheld E.H. Wachs P-2 hydraulic power head which rotates at between 012 RPM, and applies a maximum torque of 800 ft-Ibs. Rotational speed during the valve cycling at Peters Dam averaged roughly 8 RPM due to the high torque required tO Operate the large valves. Cycling the upstream high-level 60?inch butterfly valve caused the truck?engine~driven hydraulic power supply for the head to overheat and boil over hydraulic fluid from the fluid reservoir. The system was checked by a mechanic, and we resumed the following morning on the high?level outlet, which took several hours to complete. We finished the second day and occupied the entirety of the third day cycling the seven upstream controls at the inclined outlet tower. All valves cycled function well and are in good condition, but the work and torque required tO cycle the valves taxes the existing portable hydraulic valve operating equipment. As noted above, the 36- inch control valve of the primary outlet was not cycled and so no flow was released from that outlet; the upper-level outlet was cycled in a sequence chosen to minimize discharge. TMWL Inspected by J. Lowe .26 4'11; 3 Photos taken? Yes NOW Date of inspection 14 16 August 2013 ?9 cc for Owner/Book Date Of Report 26 August 2013 DWR1261 (Rev. toms) Sheet 1 of INSPECTIC DAM AND RESERVOIR IN CE STATUS Name of Darn Peters Dam No. 33-7 I Date of Inspection 14 16 August 2013 . .QCycling the upstream high-level 60-inch butterfly valve (above) caused the truck-engine-driven hydraulic power supply forthe P-2 head to overheat and boil over hydraulic fluid from the fluid reservoir. We resumed the following morning cycling the high?level outlet (below), which took several hours to complete. DWR1261(rev.10f09) Sheet 2 of 3 INSPECTIC DAM AND RESERVOIR IN CE STATUS Name of Dam Peters Dam No. 33-7 Date of inspection 14 16 August 2013 . i a . Upstream control for the fully encased normally pressurized outlet is provided by six 30-inch gate valves arrayed along a 48-inch diameter inclined outlet tower at elevations of 345.0', 333.5', 320.0?, 295.0?, 260.0?, and 215.0?, and by a single 36-inch butterfly valve at elevation 379.5? (operated by handwheel at far right). The upper reaches of the 48-inch inclined outlet tower showing the valve actuators. DWR1261(rev.10f09) Sheet 3 of 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 Peters Dam No. 33-7 County Marin Type of Dam ERTH Type of Spillway Concrete weir and chute Water is 10 feet below the spillway crest and 25 feet below the dam crest. Weather Conditions Clear and mild Contacts Made Carl Gowan during the inspection Reason for Inspection Periodic Evaluation Important Observations, Recommendations or Actions Taken As with other recent inspections, emergent coyote bushes and other woody vegetation that tends to accumulate along the face and groins continues to thrive. To limit future growth aggressive vegetative clearing that includes root removal or destruction should be performed along the face and groins. Small willow trees and woody bushes that have taken root within construction joints along the upper level outlet outfall chute remain and should be removed to prevent damage to the concrete chute invert and sidewalls. There are no prior outstanding administrative requirements. The total class weight of 26 appears satisfactory. Conclusions From the known information and visual inspection, the darn, reservoir, and the appurtenances are judged safe for continued use. Observations and Comments Dam The visible portion of the upstream face, crest, face, and abutments are in satisfactory condition with no indication of surficial distress or instability. The upstream face is armored with large riprap. Vegetation control remains generally satisfactory but coyote bushes, scotch broom, and other woody vegetation that tends to accumulate along the face and groins continues to thrive. Annual clearing of newly emergent woody species should be a priority if long-term gains are to be made against these persistent species. Similar to recent past inspections, rodent control remains satisfactory and few to no indications of rodent activity were observed. The roadway cut and hillside above the outlet tower shows no obvious signs of renewed movement. Past sliding at this location during a winter storm has reportedly caused damage to the outlet valve controls. Spillway The approach, control section, and exit channel were clear and unobstructed. The concrete walls and floor remain in good condition, with no significant indications of structural or physical deterioration. A small concrete spall on the upper right spillway invert remains, however, the larger 4' by 6? spall along the interior upper left spillway wall has been repaired by blending the spalled surface with the adjacent wall. Inspected by J. Lowe apr- 20,3 Photos taken? Yes No Date of Inspection 24 April 2013 cc for Owner/Book Date of Report 29 April 2013 er of l) DWR 1261 (Rev. 10109) Sheet? ?9 i DAM AND RESERVOIR IN STATUS Name of Dam Peters Dam No. 33-7 Date of Inspection 24 April 2013 Observations and Comments Outlet Seegage The original spiliway, now used as a discharge chute for the 60? diameter upper level outlet, remains in generally satisfactory condition. Small willow trees and woody bushes that have taken root within construction joints along the upper level outlet outfall chute should be removed to prevent damage to the concrete chute invert and sidewalls. The current design storm, prepared in 1981, is for a 170,000 year return period producing 19,900 (~947 sq mi) from the 22.1 square mile drainage area. The current TCW for this dam is 26. The spillway capacity is ~20,900 which is greater than the peak inflow. Total freeboard is 15 feet and the residual freeboard for the design storm is 2.5 feet. Freeboard is satisfactory. Upstream control for the fully encased normally pressurized outlet is provided by six 30-inch gate valves arrayed along a 48-inch diameter inclined inlet tower at elevations of 345.0?, 333.5?, 320.0?, 295.0', 260.0?, and 215.0?, and by a 36-inch butterfly vaive at elevation 379.5?. control for the inclined tower is provided by a 36-inch diameter butterfly valve near the left toe of the embankment. A separate high~level outlet controlled on both the upstream and sides by two 60-inch diameter butterfly valves provides additional outlet control. None of the outlet controls were cycled during this inspection but they are scheduled to be cycled later in the year. All of the outlet tower upstream controls were fuliy cycled and were found to be in good operating condition during the July 2009 periodic inspection. The control was last cycled and found to be in satisfactory operating condition during the April 2004 inspection. No evidence of seepage was observed along the face, abutments, or groins. Seepage from the single toe drain was estimated to be approximately 25 at the 90-degree V-notch weir. There was no seepage from the 60? diameter upper level outlet discharge, and seepage from both the left and right collar drains for the upper level outlet discharge was only a slight trickle. instrumentation consists of: Sixteen (16) survey monuments distributed along the crest and along a row near the mid elevation of the embankment, are designed to measure movement following significant seismic events, a Seventeen (17) piezometers distributed along the crest, along a row near the mid elevation of the embankment, and on the embankment above and along the toe. Piezometers are designed to measure pore pressures within the embankment and along the abutments. a One (1) seepage measurement weir located near the valve house adjacent to the outfall of the fishwater release weir. Design elevations for the piezometers are: Piezometer Depth to Bottom Design Tip Comments Number of Piezometer Elevation P-1 35.5 376.3 Clogged circa March 1999, reopened Oct. 2001 P-1A 45.0 370.7 P-2 63.3 344.8 P-3 68.1 340.5 (rev.10!09) Sheet 2 of 6 INSPECTION 5' DAM AND RESERVOIR IN STATUS Name of Dam Peters Dam No. 33-7 Date of Inspection 24 April 2013 Observations and Comments 9-4 93:9 346?9 Replaced by P-4A in 1986. P-4A Piezometer P-4 was replaced by P-4A in 1986. P-5 88.2 322.1 P-6 34.1 382.4 P-6A Critical elevation 280? P-7 57.6 266.1 4466 246?6 Abandoned and replaced by P-8A in 1986 P-8A Critical elevation 236? P9 50.0 268.3 P-10 74.2 186.6 Critical elevation 229, monitors pressure at toe P-10A 91.0 183.4 Critical elevation 230, monitors pressure at toe P-10B 70.0 179.8 Critical elevation 228, monitors pressure at toe 56.5 177.3 Critical elevation 220 66.4 177.8 Critical eievation 225 P-11B 39.0 172.2 Critical elevation 205 Survey data for the period from January 1982 through January 2011 was reviewed. The maximum cumulative settlement was reported as -0.1.58 feet (1.9 inches) at monument M-7 in March of 201 1. The maximum increase in settlement within the reviewed period is -0.155 feet (1.9 inches) at monument M-7, also in March of 2011. Alignment readings are presented and are small throughout the reviewed period. Recorded movements are within 0.05 feet (0.6 inches) with a roughly equal distribution of upstream and movement. Based on the distribution, and the small reported displacements, it appears that the results reflect primarily instrument and reading error rather than actual displacement, and that the darn remains stable with regard to alignment. The seepage measurement weir adjacent to the outfall of the fishwater release weir is designed to measure seepage from the toe drain. Measured seepage rates have varied from 0.0 to as high as 1,200 in February of 1982, reportedly the result of a combination of seepage and surface runoff foilowing a period of intense rainfall. Since April of 1983 MMWD has diverted surface drainage away from the weir pond and the maximum reported reading since that time has been 420 in February of 1986. For the January 2001 through January 2011 data period reviewed the maximum reported seepage was just over 55 in January of 2006, with average annual peak flow rates less than 20 gpm. Piezometer water surface elevations for the January 2001 through January 2011 period reviewed are stable with no significant increasing or decreasing trends, and levels remain below ?phreatic surface number which has been determined to be the maximum surface (critical elevation) for adequate stability as shown in the DSOD memorandum from V.H. Persson to J. E. Ley dated 27 July 1983. In their April 12, 2012 instrumentation data submittal letter the owner reports, ?The Peters Dam (Kent Lake) piezometers and weir ?ows are consistent with historic readings. Peters Dam (Kent Lake) is trending toward. stabilization: Settlement of -0. 12 ft (maximum) and alignment of -0. 05 feet direction; maximum). I find no alarming seepage trends or significant displacement reported for the data period. DWR1261(rev.10i09) Sheet 3 of 6 INSPECTION 7 DAM AND RESERVOIR IN STATUS Name of Dam Peters Dam No. 33-7 Date of Inspection 24 April 2013 . 2Vegetation control remains generally satisfactory but coyote bushes, scotch broom, and other woody vegetation that tends to accumulate along the face and groins continues to thrive. Annual clearing of newly emergent woody species should be a priority if long-term gains are to be made against these persistent species. The upstream face is shown above, the below. DWR1261(rev.10l09) Sheet 4 of 6 DAM AND RESERVOIR IN STATUS Name of Dam Peters Dam No. 33-7 Date of Inspection 24 April 2013 . J, II I - Jr? A dense stand of scotch broom in the upper left embankment and groin (above), and willows and other trees and bushes growing within cracks in the original concrete spillway (below). i DWR1261 (rev. 10/09) Sheet 5 of 6 INSPECTION 7 DAM AND RESERVOIR IN STATUS Name of Dam Peters Dam No. 33-7 Date of Inspection 24 April 2013 ?tr-Elba..- Jam? The lower half of the primary spillway as seen from the upper half. The spillway is in good condition but vegetation should be removed from within construction joints. ft SI it?? 354? The seepage measurement weir adjacent to the outfall of the fish-water release weir is designed to measure seepage from the toe drain. Peak flows generally average below 20 gpm. DWR1261 (rev. 10mg) Sheet 6 of