Concrete Report by CTL Group

Transcription

1 Concrete Report by CTL Group

2 Building Knowledge. Delivering Results. CONSTRUCTION TECHNOLOGY LABORATOR~ES ENGINEERS & CONSTRUCTION TECHNOLOGY CONSULTANTS CAPAY DAM YOLO COUNTY, CALIFORNIA NONDESTRUCTIVE EVALUA TlON OF MASS CONCRETE DAM 1 Report to: Stantec Consulting, Inc South 48' Street Phoenix, Arizona I I Stantec Project No Submitted by: CTLGrou p Date: April 4, 2007 CTLGroup Project No Main Office: 5400 Old Orchard Road Skokie, Illinois Phone: Fax: Mid-Atlentic Office: 9030 Red Branch Road, Suite 110 Columbia, Maryland Phone: Fax: New England Office: 1 Washington Street, Suite 300A Dover, New Hampshire Phone: Fax:

3 Capay Dam. Yolo County. CA CTLGroup Project No Page i of ii April TABLE OF CONTENTS... 1 INTRODUCTION I SCOPE OF WORK 4 3. TEST AREAS AND METHODOLOGIES IMPULSE RESPONSE (IR) MEHTOD GROUND PENETRATING RADAR (GPR) METHOD ULTRASONIC PULSE VELOCITY (UPV) METHOD LABORATORY TESTING CONCRETE CORE SAMPLING COMPRESSIVE STRENGTH TEST PETROGRAPHIC EXAMllNATlON FIELD INSPECTION AND TEST RESULTS SPILLWAY VISUAL INSPECTION IMPULSE RESPONSE TEST GROUND PENETRATING RADAR (GPR) TESTING APRON SLAB VISUAL INSPECTION IMPULSE RESPONSE TESTING GROUND PENETRATING RADAR TESTING HEADGATE STRUCTURES VISUAL INSPECTION IMPULSE RESPONSE TESTING GROUND PENETRATING RADAR TESTING ULTRASONIC PULSE VELOCITY (UPV) TESTING LABORATORY TESTING... 12

4 CTLGroup Project No Page ii of ii April 4, CORE SAMPLE LOG COMPRESSIVE STRENGTH TEST PETROGRAPHIC EXAMINATION SUMMARY PHOTOS FIGURES APPENDIX A - COMPRESSIVE STRENGTH TEST DATA APPENDIX B - PETROGRAPHIC EXAMINATION REPORT

5 CTLGroup Project No Page 1 of 19 April 4,2007 CAPAY DAM, YOLO COUNTY, CA CONDITION ASSESSMENT AND NONDESTRUCTIVE EVALUATION 1 Peter B. Foster 2 Honggang Cao Malcolm Lim3 1. INTRODUCTION In September of 2006, CTLGroup was contracted by Stantec Consulting, Inc. headquartered in Phoenix, Arizona (Stantec) to evaluate the condition of the Capay Dam, located on Cache Creek in Yolo County, California. The dam was reportedly built in 1914, consisting primarily of the concrete overflow spillway, reinforced apron slab and two headgate structure. The overflow section of the dam, or spillway, is approximately 475 feet in length and 10 feet in height. It is approximately 4 feet wide at the crest and 10 feet wide at the bottom (see Figure 1). Reportedly, a portion of the apron slab failed and was subsequently repaired in At some point, a concrete topping (overlay or veneer) was placed on the downstream face of the dam. In 1993, the uppermost 18 inches of the dam was removed and replaced and the dam geometry altered to include an inflatable rubber bladder, which allowed for increased water surface elevation. CTLGroup evaluated the current conditions of dam structures, using a variety of nondestructive testing techniques, coupled with visual inspection and laboratory testing on removed samples. The field investigation was performed on October 23-27, 2006, after the downstream side of the dam was dewatered. The concrete core locations were selected by CTLGroup, while the extraction of concrete cores was conducted by Stantec in the following week. Laboratory testing and data analysis took place in CTLGroup office in Skokie, IL in December, This report covers the test program, methodologies, findings and conclusions. Associate 1, CTLGroup, 5400 Old Orchard Rd., Skokie, IL Project Manager, CTLGroup, 5400 Old Orchard Rd., Skokie, IL Group Manager, CTLGroup, 5400 Old Orchard Rd., Skokie, IL

6 CTLGroup Project No Page 2 of 19 April 4, OBJECTIVE AND SCOPE OF WORK The objective of the evaluation was to assess the existing condition of the dam, including the downstream face of spillway, apron slab and two headgate structures (see Photo 1). Specifically, the evaluation program included the following: 1) Assessment of internal defects or deterioration in concrete, such as significant honeycombing or voiding, delamination and cracking, deterioration of concrete material quality, etc. 2) Loss of support underneath the apron slab 3) Evaluation of embedded reinforcing bars and their configurations CTLGroup's scope of work in this evaluation included: 1) Field Investigation: Selection of representative test areas Visual inspection at areas associated with testing Nondestructive testing : Impulse Response (IR) - Ultrasonic Pulse Velocity (UPV) - Impulse radar (Ground Penetrating Radar or GPR) Selection of core locations 2) Laboratory testing on cores: Compressive strength testing Petrography examination 3) Data analysis and generating project report

7 CTLGroup Project No Page 3 of 19 April 4, TEST AREAS AND METHODOLOGIES The top surface, downstream face, apron slab and the two headgates were nondestructively evaluated using Impulse Response (IR), Ground Penetrating Radar (GPR).and Ultrasonic Pulse Velocity (UPV, on headgates only) tests. All test areas and core locations are shown in Figure 2. The top surface of the dam was evaluated in four test areas equally spaced along the length of the dam. Each test area was 50 feet in length and extended from the downstream edge to the inflated bladder, which was approximately 8 feet in width. The apron slab was evaluated in four areas. Due to constraints that existed on the apron slab, the test areas varied from 21 to 39 feet in length and 9 to 15 feet in width. The downstream face of the dam was evaluated primarily in areas where the concrete overlay has spalled off. A total of six areas were tested, which varied from 20 to 48 feet in width and 5 to 8 feet in height. One area near the north end of the dam (around Station 4+60) was evaluated on the upstream face as this area became accessible after the river was rerouted away from the northern end of the dam. The area tested was approximately 5 feet in height and had a length of 26 feet Portions of the retaining wall and rib supports of the two headgates were evaluated using IR, GPR and UPV methods. 3.1 IMPULSE RESPONSE (IR) METHOD Impulse Response test was employed to evaluate the uniformity of concrete and possible presence of internal defects such as cracks, honeycomb, voiding etc. A total of 19 test areas were evaluated which included 6 on the downstream face of the dam, 1 on the upstream face of the dam, 4 on the top surface of the dam, 4 on the apron slab and 4 areas divided between the two headgates (see Figure 1). Photo 2 shows the IR test method performed on the top of the dam. The Impulse Response (IR) test is fully described in American Concrete Institute report ACI "Nondestructive Test Methods for Evaluation of Concrete in Structures". The IR method uses a low strain impact to send a stress wave through the tested element. The impactor is a l-kg sledgehammer with a built-in load cell in the hammerhead. The maximum compressive stress at the impact point in concrete is directly related to the elastic properties of the hammer tip. Typical stress levels range from 5 MPa for hard rubber tips to more than 50 MPa for aluminum tips. Response to the input stress is normally measured using a velocity transducer (geophone). Both the hammer and the geophone are linked to a portable field computer for data acquisition and storage. The data are processed using the Fast Fourier

8 CTLGroup Project No Page 4 of 19 April 4, 2007 Transform (FFT) algorithm. The resulting velocity spectrum is divided by the force spectrum to obtain a transfer function, referred to as the Mobility of the element under test. The test graph of Mobility plotted against frequency over the 0-1 khz range contains information on the condition and the integrity of the concrete in the tested elements. The mean mobility value over the khz range is referred as Average Mobility with units of [(m/s)/n x10-'1. Its value is directly related to the modulus of elasticity, density and the thickness of the test element such as a wall or slab. In general, the presence of an internally delaminated layer, weakened layer or bond, will result in an increased average mobility value. On the other hand, a sound concrete element without distress will reduce the average mobility value. The test results can be analyzed and presented in the form of contour plots. The relatively weaker areas can be identified through a scaled color scheme. The typical influence depth of the testing is about 2 feet from the testing surface.

9 CTLGroup Project No Page 5 of 19 April 4, GROUND PENETRATING RADAR (GPR) The lmpulse Radar (Ground Penetrating Radar or GPR) testing was performed to evaluate the as-built reinforcing bar configuration, assess the concrete cover, and facilitate the removal of concrete cores to avoid cutting the reinforcing steel. GPR test was performed in the same test areas where IR test was conducted. Photo 3 shows the lmpulse Radar technique used on the apron slab. The lmpulse Radar technique is described in American Concrete Institute report ACI "Nondestructive Test Methods for Evaluation of Concrete in Structures". The lmpulse Radar or Ground Penetrating Radar technique employs high-frequency electromagnetic energy waves for rapidly and continuously assessing a variety of characteristics of concrete structures. The principle of operation is based on reflection of electromagnetic waves from varying dielectric constant boundaries in the material being probed. The impulse radar equipment is self-contained, compact, and portable. The system consists of the main radar unit, antenna and transducer cable. All data is stored in the main radar unit, by means of a computer hard drive. A single or double contacting transducer (antenna) transmits and receives radar signals. High frequency, short pulse electromagnetic energy is transmitted into the element under test. Each transmitted pulse travels through the material, and is partially reflected when it encounters a change in dielectric constant. The receiving section of the transducer detects reflected pulses. The location and depth of the dielectric constant boundary is evaluated by noting the transit time from start of pulse to reception of reflected pulse. Boundary depth is proportional to transit time. Since interfaces between concrete and air, water, and/or backfill are electronically detected by the instrument as dielectric constant boundaries, the impulse radar method is capable of assessing a variety of reinforced concrete, masonry and environmental characteristics. lmpulse radar technique is frequently used to evaluate locations of reinforcing bars, and other embedded foreign objects in concrete element.

10 CTLGroup Project No Page 6 of 19 April 4, ULTRASONIC PULSE VELOCITY (UPV) METHOD The Ultrasonic Pulse Velocity (UPV) test was employed to evaluate the uniformity of concrete present in the headgate rid support structures. Unfortunately, the surface of the headgate structures was too rough to facilitate consistent and accurate measurements. Therefore, the UPV method was abandoned and the results considered unreliable for this assessment. The Ultrasonic pulse velocity (UPV) test method is fully described in ASTM Standard C-597 "Standard Test Method for Pulse Velocity through Concrete" and American Concrete Institute report ACI "Nondestructive Test Methods for Evaluation of Concrete in Structures". This method uses an ultrasonic pulse to generate a compression wave through the concrete element being tested. Typically, a direct transmission method ("pitch-catch") is used. The pulse is directed into the concrete through a transmitter, and received by a receiver on the opposite side of the element under test. The pulse tends to be rapidly attenuated in the concrete and maximum transmission path lengths in good concrete are in the order of 6 feet. The Ultrasonic Pulse Velocity is calculated by dividing the pulse path length by the pulse travel time. The UPV is primarily a function of both the concrete dynamic elastic modulus and its density. Where anomalies such as cracking and low density concrete are present, the velocity of the wave transmission is considerably reduced. 3.4 LABORATORY TESTING CONCRETE CORE SAMPLING The core locations were selected based on results of visual inspection and Impulse Response testing. The Impulse Radar was performed to evaluate the location of the reinforcing bars in concrete to facilitate coring operation. A total of nineteen cores were retrieved from the dam: seventeen cores were marked by CTLGroup and used for evaluation, the other two additional cores were retrieved during the geotechnical exploration. Of the seventeen cores marked by CTLGroup, four cores were retrieved from the two headgate structures and the others were retrieved from the downstream face, apron slab and top of the dam structure. The diameters of cores removed were either 4 inches or 6 in, with depths varied from 6 inches to approximately 5 feet

11 CTLGroup Project No Page 7 of 19 April 4, COMPRESSIVE STRENGTH TEST The compressive strength test was performed on a total of ten core samples to assess the general level of strength of concrete and its uniformity in the dam structure. The compressive strength test was performed in accordance with ASTM C42 "Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete" PETROGRAPHIC EXAMllNATlON The petrographic examination was performed on a total of four core samples to assess the concrete condition at microscopic level. The examination was conducted in accordance with ASTM C , "Standard Practice for Petrographic Examination of Hardened Concrete." 4. FIELD INSPECTION AND TEST RESULTS 4.1 OVERFLOW SECTION OF THE DAM 4.1.I Visual Inspection The overflow section of the dam (spillway), was visually inspected at areas associated with testing and sampling. The surface of the crest appeared to be in sound condition. The concrete overlay at the downstream face had sporadic spalling and debonding (see Photos 4 to 6). The exposed portion of underlying spillway concrete appeared to be in sound condition, relative to the age of the structure in service. However, varying degree of weathering and deterioration were noted on the surface, such as large area scaling. At approximately station 260' (from the south end) there was a rock pocket about 2 feet x 2 feet (see Photos 6 to 7). Horizontal and vertical cracks were noted in several locations. These cracks appeared to coincide with the construction joints formed during the construction of the dam (see Photo 8 and 9). The vertical construction joints were noted at intervals of approximately 22 feet, while there also appears to be a horizontal joint at approximately mid height. The upstream face of the dam at the section tested (north end) appeared to be in good condition. All items identified are noted on the NDT results in Figures Impulse Response Test The results of the IR testing performed are shown in Figures 3-7. As seen in these figures, the average mobility varied among different types of element, i.e. the results for the spillway will

12 CTLGroup Project No Page 8 of 19 April 4,2007 differ from that for the apron or headgates. This is due to the response of the structure; i.e. thicker elements respond differently than thinner, more flexible elements. The IR results for the top surface of the dam spillway indicated that the average mobility was consistent across the length of the dam. The majority of the test points had an average mobility of 3.5 or less, indicating uniform quality across the crest of the spillway. In addition, the bond between the original and replaced portions of the crest appeared to be in sound condition. Several test points had average mobility larger than 3.5, which might indicate presence of honeycomb at the test points or a relatively weaker bond at the interface between the original and newly replaced concrete. However, these points are highly localized and sporadic. No palpable delamination or debonding was noted within the replaced concrete portion. The downstream face of the spillway was evaluated in six areas. These test areas were selected primarily in sections where the concrete overlay (veneer) had spalled off. In general, the downstream face of the dam was in good condition, indicated in green in Figures 3-7. The areas with high mobility (in red) were generally at the delaminated section of the concrete overlay. While most of the concrete overlay is still intact, such as in Test Area F1, overlay delamination existed in the vicinity of existing spalling. In the areas of substrate concrete indicated in yellow, one of the following can be considered to be present: Localized near surface honeycombing or delamination Weakened or deteriorated concrete (often resulting in low compressive strength) In Test Area F5, a visible rock pocket was observed (as indicated in the visual inspection) and a second anomaly, possibly a hidden rock pocket, was found to exist approximately 6 feet to the left and 1 foot above the visible pocket, based on IR test results. In general, the IR tests results in the six tested areas showed only localized defects. IR testing was also performed on a section of the upstream face of the dam (see Figure 2). The concrete appeared to be uniform in response. No significant internal defect was noted. Photo 10 shows the IR testing in progress Ground Penetrating Radar (GPR) Testing GPR testing was performed both vertically and horizontally on the surface of spillway. No reinforcing bar was noted within 16 inches from the surface. Radar scans performed on the top surface of the spillway revealed that reinforcing steel was spaced at approximately 12 inches on center and was oriented perpendicular to the length of the dam. In general, the reinforcing steel

13 CTLGroup Project No Page 9 of 19 April 4,2007 present in the top surface was consistent with the design configuration shown in the design drawings. 4.2 APRON SLAB Visual Inspection The surface of the apron slab is eroded and uneven. The original timber plank cover has not been replaced since the 1940's. In addition, there was sporadic transverse cracking on the surface (see Photos 11 to 13), with many coinciding with construction joints Impulse Response testing The results of the IR testing performed are shown in Figures 3-7. As seen in these figures, the areas in red indicate presence of thinner apron slab and 1 or loss of underneath soil support, particularly in Test Area 4, which was immediately adjacent to the section of the apron slab failed in In general, the test points near the intersection of the dam downstream face and apron slab have a significantly lower average mobility than those further away from this point. The lower average mobility was attributed to largely increased mass under the slab. This indicates that the interior cut-off wall may be present at these locations. In Test Area 3, delamination could be present in the slab as the portion with cutoff wall near the edge of the apron slab exhibited higher mobility values. Similarly, the higher mobility values were noted in Test Area 1. In the other tested areas, loss of support and I or thinner slab appeared to be localized. The core samples removed from the apron (see section 5.1) indicate large variation in slab thickness, from 14 inches to 22 inches, while the design thickness was about 18 inches Reportedly (from the on-site coring crew), no significant cavities underneath the slab were noted at the core locations. It was believed that the considerable variation in slab thickness and internal delamination were the major cause in large variation of average mobility values. However, intermittent loss of support (could be small detachment between supporting soil and slab soffit) were noted in some areas, such as Test Area A4. Detailed interpretations of the results are shown in the Figures Ground Penetrating Radar Testing The apron slab was found to have reinforcing bars running perpendicular to the length of the dam and spaced at approximately 2 feet center-to-center. A core removed (C8) from the slab

14 CTLGroup Project No Page 10 of 19 April 4, 2007 contained a reinforcing bar, it appeared to be a twist bar, measured 314 inches (smallest dimension) to 1 inches (largest dimension). In general, the distance between concrete surface and noted reinforcing bars ranged from 8 inches to 15 inches at tested areas. Therefore, the bars can be considered to be placed in middle to lower section of apron slab. There did not appear to be any reinforcing steel parallel to the length of the dam present in the apron slab. Radar scans along the edge of slab (scan over the cutoff wall) revealed that the reinforcing steel did not continue through this portion of the structure. Instead, the reinforcing steel terminated near the intersection of the apron slab and cutoff wall although the exact location could not be determined due to the presence of timber planking at this location. The voided areas (see Test Area A3 and A4) mentioned during the discussion of IR results were also detected in the Impulse Radar testing. 4.3 HEADGATE STRUCTURES Photo 14 shows the overview of headgate structures. Due to the limited access, all inspection and testing were performed only at the upper half of structure Visual Inspection Similar observations were noted at both north and south headgate structures. a) Concrete deck The concrete deck was 2 feet in width and 8 inches in thickness. Severe cracking and concrete spalling was noted along the soffit of deck. At multiple locations, severe corrosion on reinforcing bars had resulted in the loss of concrete cover and bar exposure (see Photos 15 to 17). There were three longitudinal linches diameter twist bar (with rib) near the slab bottom of the deck. The concrete cover was within approximately 1 inches b) Retaining wall The retaining wall appeared to be in good condition. No significant deterioration was noted. The thickness of wall is approximately 6 inches. c) Rib support In general, the concrete rib support was in relatively sound condition. Surface scaling and very localized spalling was present (see Photos 18 to 19).

15 CTLGroup Project No Page 11 of 19 April 4, Impulse Response Testing Impulse Response testing was performed on a section of retaining wall and a piece of rib support at each headgate. The average mobility values appeared to be dominated by the structural supports, i.e. near support areas demonstrated low mobility while the mid span (far from supports) demonstrated high mobility. However, the results appeared to be consistent. No indication of internal delamination or loss of support was palpable. The test results are shown in Figure Ground Penetrating Radar Testing GPR testing was performed in the areas that were tested on both the retaining wall and rib support element. The purpose of these scans was to verify steel reinforcement locations and core positions. a) Concrete deck The GPR testing confirmed the presence of three longitudinal bars, while no transverse bars were noted. b) Retaining wall One layer of steel reinforcement was located at approximately 12 inches on center in both vertical and horizontal orientations, positioned close to the exposed 1 testing face. c) Rib support No reinforcing bars were noted in the rib support elements Ultrasonic Pulse Velocity (UPV) Testing UPV testing was performed at the two rib support elements. However, the readings were largely scattered due to the poor contact between the transducers and the rough concrete surface. It was deemed that the test was not suitable and therefore abandoned.

16 CTLGroup Project No Page 12 of 19 April 4, LABORATORY TESTING 5.1 CORE SAMPLE LOG A total of nineteen (19) core samples were removed from the Capay Dam for several evaluation purposes, including calibration of NDT results, petrographic examination and compressive strength testing. Upon arrival at CTLGroup, the cores were visually inspected. The core locations, lengths and observations are shown in Table. I. Photographs showing the conditions of cores as received are presented in Photos 20 to 39. Only the cores marked by CTLGroup are presented in this report. These include Cores 1 through 18 excluding Core # 14 which was not retrieved from the upstream face of the dam. It is apparent that the coring operation resulted in several cores being damaged within the core sample. The cores that were damaged in general had a large piece of aggregate on one side of the fracture plane. The majority of these pieces of large aggregate were about 4 inches in diameter.

17 CTLGroup Project No Page 13 of 19 April 4, 2007 TABLE 1: CORE LOG Cor L C1 C2 Statio n I 6 Element Apron [I I ' from edge] DSF [5' above toe] Length [inches] Core Observation Core in 5 pcs. ranging from 5 inches to 11.5 inches; Cracked at locations of large aggregate; cut-off wall Core in good condition Core Size [inches] 6 4 C3 C Apron [I 0' from edge] DSF [3' above toe] Core in 7 pcs. ranging to 20 inches; Depth of crack found to be -1 4 inches; cut-off wall Core in 7 pcs ranging to 12 inches; Const. joint visible along entire length 4 4 C DSF [8' above toe] 12 Core had multiple micro-cracking parallel to the surface 4 C DSF [5' above toe] 12 Core in 2 pcs; 4 inches and 9 inches; Relatively clean core 4 C7 C DSF [3' above toe] Apron [5' from edge] Visible crack at -5 inches depth; Core in distressed condition; Powdery substance on bottom of Core in good condition 4 6 C Top [I' from DSF] 12 Core in good condition 4 C DSF [2' above toe] 12 Core in good condition 4 C DSF [5' above toe] 18 Core in good condition 4 C Apron [ 2' from toe] 14 Core in good condition 6 C Apron [5' from edge] 12 Core in relatively good condition; Top and bottom of core very rough 4 C USF [ 2' above base] Not retrieved from upstream face of dam C Left Headgate - Rib 12 Core in good condition 4 C16 C17 C Left Headgate -Wall Right Headgate - Rib Right Headgate - Wall Crack visible along length of core; core very rough Outer 3 inches of core very rough with many small voids Core very rough and had many small voids Note: 1) DSF - Downstream face USF - Upstream face 2) C14 was not retrieved. There are a total of 17 cores obtained for evaluation by CTLGroup.

18 CTLGroup Project No Page 14 of 19 April 4, COMPRESSIVE STRENGTH TEST A summary of the compressive strength test results is shown in Table 2. The compressive strength of spillway at downstream face ranged from 2,090 psi to 4,990 psi with average of 3,704 using five results (C2, C5, C6, C10 and CIA). The lowest compressive strength occurred in the downstream face of the dam at the location of core C5 (see Figure 4). The replacement concrete at crest had a higher compressive strength of 7,200 psi (C9). The compressive strength of apron ranged from 3,360 psi to 5,180 psi. The data generated from the physical testing of the core samples is shown in Appendix A. TABLE 2: COMPRESSIVE STRENGTH TEST RESULTS

19 CTLGroup Project No Page 15 of 19 April 4, PETROGRAPHIC EXAMINATION Four cores were sent for petrographic examinations, namely C1, C7, C8 and C17. The results of the petrographic examination indicated that, in general, the concrete of the dam structure is in good condition given the age of the dam. Varying degrees of weathering and deterioration of the concrete is evident along the exposed outer surface of each of the four cores. The cause of surface deterioration is uncertain, but may be related to one or more of the following: 1) impact or scouring with sediment in the water discharge, 2) damage related to cyclic freezing and thawing of the non-air-entrained concrete (provided the concrete is exposed to such conditions), and 3) long-term leaching and erosion from flowing andlor mildly aggressive water. Sparse surface-parallel hairline cracking was observed in the outer portions of a few cores. No evidence of significant alkali-silica reaction or other apparent causes of cracking in the body of concrete were apparent. Again, such damage could be related to cyclic freezing, if the structure is exposed to such conditions. Also, some localized damage is evident in areas of honeycombed concrete in the lower portion of Core C7. This honeycombed concrete exhibits evidence of apparent in-situ leaching and secondary deposits. Such poor consolidation of the concrete is not observed in the other cores. Microscopical examination of the samples also revealed evidence of fairly extensive leaching of constituents, mainly calcium, from the cement paste binder throughout most of the depth of the cores. This is evident from examination of petrographic thin sections produced from various depths in the outer approximately 6 to 12 inches of each core that show very little to no crystals of portlandite (calcium hydroxide) in the paste. Leaching may be related to long-term movement of moisture through the concrete. Also, water retained by the dam should be further evaluated for its aggressivity. "Soft" and acidic water may promote excess leaching and erosion of concrete surface. With possible exception to softening and erosion of exposed concrete surfaces, no clearly apparent deleterious effects of the leaching were evident in the concrete samples. Such leaching may reduce the ph of the concrete. However, based on staining tests using ph-indicator (phenolphthalein) solution on cross sections of the cores, the ph appears to be above 10. These stain tests also show that the depth of carbonation in the cores is fairly shallow, given the age of the structure. The petrographic report of the cores examined is presented in Appendix B.

20 CTLGroup Project No Page 16 of 19 April 4, SUMMARY CTLGroup performed field investigation including nondestructive testing at Capay Dam, and the subsequent laboratory testing and analysis on extracted core samples. A total of nineteen individual test areas with varying sizes throughout the spillway, apron and headgates were inspected and nondestructively tested. A total of nineteen cores were extracted, in which seventeen were used for evaluation by CTLGroup. Petrographic examination was conducted on four cores while the compressive strength test was conducted on a total of ten cores. The primary findings are summarized below: Overflow Section of Dam (Spillway) 1) The inspection was performed mainly on the downstream face of the spillway due to the access. The concrete overlay (veneer) had spalled off in several areas, exposing original substrate concrete. Varying degree of weathering and deterioration had taken place on the original concrete in the exposed areas, exhibiting large scaling, localized spalling and rock pocket. Vertical construction joints were spaced at about 22 feet apart, while horizontal joints could be seen along approximately mid height of the spillway in exposed areas. Several observable vertical construction joints are associated with cracking. The cause of surface deterioration may be related to one or more of the following: 1) impact or scouring by sediment in the water discharge, 2) damage related to cyclic freezing and thawing the non-air-entrained concrete (provided the concrete is exposed to such conditions), and 3) long-term leaching and erosion from flowing and/or mildly aggressive water. 2) The spillway appears to be unreinforced based on GPR testing, except for the newly placed concrete at the crest, where reinforcing bars were noted to be placed 12 inches on center, perpendicular to the length of dam. 3) Through nondestructive Impulse Response testing, internal delamination and / or honeycombing near surface were noted. However, they appear to be fairly localized and sporadic. Under microscope, this honeycombed concrete exhibits evidence of apparent in-situ leaching and secondary deposits. 4) The compressive strength of the cores removed from the spillway show a large variation from 2,090 psi to 4,990 psi with average of 3,704 psi. This variation is in part due to the

21 CTLGroup Project No Page 17 of 19 April 4,2007 large size aggregate used in concrete mix, often up to 4 inches Also, varying degree of deterioration and leaching at different locations exacerbated the strength variation. 5) In general, the concrete in the spillway was well consolidated, non-air-entrained. Aggregate used in the concrete appears to be fairly well graded. Coarse and fine aggregates used in the concrete are predominantly hard and firm and judged to be of good quality. Extensive leaching was noted, especially at regions near surface. With possible exception to softening and erosion of exposed concrete surfaces, no clearly apparent deleterious effects of the leaching were evident in the concrete samples. Apron 6) The surface of the apron slab is eroded and uneven, primarily due to impact or scouring due to gravel in the flow overtopping the spillway. The original timber plank cover was has not been replaced since the 1940's. In addition, there is sporadic transverse cracking on the surface with many coinciding with construction joints. 7) Impulse Response testing and GPR testing revealed large variation of apron slab thickness, from approximately 14 inches to 22 inches (as evidenced by core samples). The Test Area A4 near the failed portion of apron showed typically thinner slab thickness, coupled with possible intermittent loss of support (could be small detachment between supporting soil and slab soffit). However, no significant cavity underneath the apron was reported by the coring crew. Internal delamination might exist in the apron slab in Test Areas A1 and A3, which were believed to be localized. 8) The approximately 4 feet wide cutoff wall under the toe of the spillway was noted during the nondestructive testing. Two cores removed from this portion showed the depth of cutoff wall ranged from 44 inches (toward south end) to 66 inches (toward north end). 9) In the apron slab, reinforcing bars running perpendicular to the length of the dam was noted and spaced at approximately 2 feet center-to-center. The reinforcement appears to be twist bar, measured % inches (smallest dimension) to 1 inches (largest dimension). In general, the distance between concrete surface and noted reinforcing bars ranged from 8 in to 15 inches at tested areas. There does not appear to be any reinforcing steel parallel to the length of the dam present in the apron slab. Radar scans along the edge of slab (scan over the support beam) revealed that the reinforcing steel does not continue through this portion of the structure.

22 CTLGroup Project No Page 18 of 19 April 4, )The concrete in the apron appears to be well consolidated and graded, non-air entrained. No significant deterioration of concrete material was noted. 11)The compressive strength of concrete in the apron ranges from 3,360 psi to 5,180 psi based on testing of three core samples. Headgates 12)The concrete deck of the headgates was measured 2 feet in width and 8 inches in thickness. Severe cracking and concrete spalling was noted along the soffit of the deck. At multiple locations, severe corrosion on reinforcing bars had resulted in the loss of concrete cover and bar exposure. There were three longitudinal 1 inches diameter (with rib) twist bars near each slab bottom. The deck should be replaced or retrofitted in near future. 13)The retaining wall and rib support structures appeared to be in good condition. No significant deterioration was noted. The thickness of wall is approximately 6 inches. 14) Impulse Response testing and GPR performed on the retaining wall and rib support structures did not indicate presence of internal defects or loss of supports. One layer of steel reinforcement was noted in the retaining wall at approximately 12 inches on center in both vertical and horizontal orientations, positioned close to the exposed / testing face. No reinforcing bars were noted in the rib support structures. 15)Compressive strength test performed using one core sample removed from the left headgate rib support registered 4,530 psi. 16)Concrete in the upper approximately 3 to 4 inches of the wall, based on petrographic examination, was considerably weaker and more porous than in the remaining lower portion of the core. The findings of the examination suggested that the weaker quality of the near-surface concrete is likely related to under-consolidation of the concrete, higher water-cement ratio, and possibly excessive water leaching. 7. CONCLUSION Based on the field and laboratory findings, it is CTLGroup's opinion that the Capay Dam structures, including spillway, apron and headgates, appear to be in overall good condition given the age of structure. Varying degree of weathering, deterioration over time, leaching and

23 CTLGroup Project No Page 19 of 19 April 4, 2007 possibly under-consolidation appear to have "softened" the region near surface. The concrete materials are typically well consolidated in deeper sections of concrete and graded despite localized honeycomb in the spillway. The observed leaching and reduced ph environment (still above 10) does not show significant deleterious effects on the concrete, other than possible erosion to the concrete surface. Structural review of the apron is recommended to be performed in view of the large variation of slab thickness, especially at areas close to the failed portion of apron, coupled with intermittent loss of support, localized internal delamination and increased water head due to the installation of the inflatable rubber bladder.

24 CTLGroup Project No January 29, 2007 PHOTOGRAPHS

25 CTLGroup Project No January 29, 2007 Headgate Downstream Face of Dam Apron PHOTO 1 DAM STRUCURE

26 CTLGroup Project No January 29, 2007 PHOTO 2 IR TEST ON THE TOP OF THE DAM

27 CTLGroup Project No January 29, 2007 PHOTO 3 GROUND PENETRATING RADAR ON APRON SLAB

28 CTLGroup Project No January 29, 2007 Overlay Spalling PHOTO 4 CONCRETE OVERLAY SPALLING ON DONWSTREAM FACE

29 CTLGroup Project No January 29, 2007 PHOTO 5 A LARGE AREA OVERLAY SPALLING ON DAM SURFACE

30 CTLGroup Project No January 29, 2007 PHOTO 6 CONCRETE SCALING ON DOWNSTREAM FACE

31 CTLGroup Project No January 29, 2007 PHOTO 7 ROCK POCKET WITH FUNGI NOTED ON DOWNSTREAM FACE

32 CTLGroup Project No January 29, 2007 PHOTO 8 VERTICAL CONSTRUCTION JOINT ON DAM FACE

33 CTLGroup Project No January 29, 2007 PHOTO 9 HORIZONTAL CONSTRUCTION JOINT AND VERTICAL CRACK ASSOCIATED WITH VERTICAL CONSTRUCTION JOINT

34 CTLGroup Project No January 29, 2007 PHOTO 10 IR TESTING IN PROGRESS

35 CTLGroup Project No January 29, 2007 PHOTO 11 APRON SLAB (1)

36 CTLGroup Project No January 29, 2007 PHOTO 12 APRON SLAB (2)

37 CTLGroup Project No January 29, 2007 PHOTO 13 APRON SLAB (3)

38 CTLGroup Project No January 29, 2007 RETAINING WALL RIB SUPPORT FOUNDATION PHOTO 14 HEADGATE STRUCTURES

39 CTLGroup Project No January 29, 2007 PHOTO 15 CONCRETE SPALLING AND REBAR CORROSION AT DECK SOFFIT (1)

40 CTLGroup Project No January 29, 2007 PHOTO 16 CONCRETE SPALLING AND REBAR CORROSION AT DECK SOFFIT (2)

41 CTLGroup Project No January 29, 2007 PHOTO 17 CONCRETE SPALLING AND REBAR CORROSION AT DECK SOFFIT (3)

42 CTLGroup Project No January 29, 2007 PHOTO 18 RIB SUPPORT OF HEADGATE STRUCTURE (1)

43 CTLGroup Project No January 29, 2007 PHOTO 19 RIB SUPPORT OF HEADGATE STRUCTURE (2)

44 CTLGroup Project No January 29, 2007 PHOTO 20 CORE 1 PHOTO 21- CORE 2

45 CTLGroup Project No January 29, 2007 PHOTO 22 CORE 3 (LOWER SECTION) PHOTO 23 CORE 3 (UPPER SECTION 1)

46 CTLGroup Project No January 29, 2007 PHOTO 24 CORE 3 (UPPER SECTION 2) PHTOT 25 CORE 4

47 CTLGroup Project No January 29, 2007 PHOTO 26 CORE 5 PHOTO 27 CORE 6

48 CTLGroup Project No January 29, 2007 PHOTO 28 CORE 7 (LOWER SECTION) PHOTO 29 CORE 7 (UPPER SECTION)

49 CTLGroup Project No January 29, 2007 PHOTO 30 CORE 8 PHOTO 31 CORE 9

50 CTLGroup Project No January 29, 2007 PHOTO 32 CORE 10 PHOTO 33 CORE 11

51 CTLGroup Project No January 29, 2007 PHOTO 34 CORE 12 PHOTO 35 CORE 13

52 CTLGroup Project No January 29, 2007 PHOTO 36 CORE 15 PHOTO 37 CORE 16

53 CTLGroup Project No January 29, 2007 PHOTO 38 CORE 17 PHOTO 39 CORE 18

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61 Client: Stantec Consulting CTLGroup Proj. No.: Project: Capay Dam in Yolo CTLGroup Proj. Mgr.: H. Cao Contact: Mr. George Sabol Technician: P. Brindise Submitter: Peter Foster, CTLGroup Approved: W. Morrison Date: January 4, 2007 Test Results of ASTM C 42/C 42M-04, "Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete" Core Identification C-2 C-3 C-5 C-6 Nominal Maximum Aggregate Size (in.) Concrete Age at Test (days) Not Stated Not Stated Not Stated Not Stated Moisture Condition at Test Dry as rec'd Dry as rec'd Dry as rec'd Dry as rec'd Orientation of Core Axis in Structure Not Stated Not Stated Not Stated Not Stated Diameter 1, (in.) Diameter 2, (in.) Average Diameter (in.) Cross-Sectional Area (sq in.) Length Trimmed (in.) Length Capped (in.) Weight in Air (lb) Weight in Water (lb) Calculated Unit Weight (pcf) Loading Rate (psi/sec) Maximum Load (lb) 51,500 69,600 23,000 55,200 Uncorrected Compressive Strength (psi) 4,770 4,070 2,090 4,990 Ratio of Capped Length to Diameter (L/D) Correction Factor (ASTM C42) Corrected Compressive Strength (psi) 4,770 4,770 2,090 4,990 Fracture Pattern Type II Type II Type I Type I Notes: Type I fracture pattern represents reasonably well-formed cones on both ends, less than 1 in. of cracking through caps. Type II fracture pattern represents a well-formed cone on one end, vertical cracks running through caps, no well-defined cone on other end.

62 Client: Stantec Consulting CTLGroup Proj. No.: Project: Capay Dam in Yolo CTLGroup Proj. Mgr.: H. Cao Contact: Mr. George Sabol Technician: P. Brindise Submitter: Peter Foster, CTLGroup Approved: W. Morrison Date: January 4, 2007 Test Results of ASTM C 42/C 42M-04, "Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete" Core Identification C-9 C-10 C-11 Nominal Maximum Aggregate Size (in.) Concrete Age at Test (days) Not Stated Not Stated Not Stated Moisture Condition at Test Dry as rec'd Dry as rec'd Dry as rec'd Orientation of Core Axis in Structure Not Stated Not Stated Not Stated Diameter 1, (in.) Diameter 2, (in.) Average Diameter (in.) Cross-Sectional Area (sq in.) Length Trimmed (in.) Length Capped (in.) Weight in Air (lb) Weight in Water (lb) Calculated Unit Weight (pcf) Loading Rate (psi/sec) Maximum Load (lb) 79,800 31,800 40,000 Uncorrected Compressive Strength (psi) 7,240 2,940 3,730 Ratio of Capped Length to Diameter (L/D) Correction Factor (ASTM C42) Corrected Compressive Strength (psi) 7,200 2,940 3,730 Fracture Pattern Type I Type II Type II Notes: Type I fracture pattern represents reasonably well-formed cones on both ends, less than 1 in. of cracking through caps. Type II fracture pattern represents a well-formed cone on one end, vertical cracks running through caps, no well-defined cone on other end.

63 Client: Stantec Consulting CTLGroup Proj. No.: Project: Capay Dam in Yolo CTLGroup Proj. Mgr.: H. Cao Contact: Mr. George Sabol Technician: P. Brindise Submitter: Peter Foster, CTLGroup Approved: W. Morrison Date: January 4, 2007 Test Results of ASTM C 42/C 42M-04, "Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete" Core Identification C-12 C-13 C-15 Nominal Maximum Aggregate Size (in.) Concrete Age at Test (days) Not Stated Not Stated Not Stated Moisture Condition at Test Dry as rec'd Dry as rec'd Dry as rec'd Orientation of Core Axis in Structure Not Stated Not Stated Not Stated Diameter 1, (in.) Diameter 2, (in.) Average Diameter (in.) Cross-Sectional Area (sq in.) Length Trimmed (in.) Length Capped (in.) Weight in Air (lb) Weight in Water (lb) Calculated Unit Weight (pcf) Loading Rate (psi/sec) Maximum Load (lb) 58,000 55,600 50,000 Uncorrected Compressive Strength (psi) 3,380 5,180 4,530 Ratio of Capped Length to Diameter (L/D) Correction Factor (ASTM C42) Corrected Compressive Strength (psi) 3,360 5,180 4,530 Fracture Pattern Type II Type III Type III Notes: Type II fracture pattern represents a well-formed cone on one end, vertical cracks running through caps, no well-defined cone on other end. Type III fracture pattern represents columnar vertical cracking through both ends, no well-formed cones.

64 REPORT OF CONCRETE PETROGRAPHY Date: January 15, 2006 CTLGroup Project No.: Re: Petrographic Examination of Cores Taken From the Capay Dam in Yolo, County, California Four concrete core samples, identified Cores C1, C7, C8, and C17, respectively (Figs. 1 through 6), were received on December 5, 2006 from Mr. Honggang Cao, CTLGroup Engineer, on behalf of Stantec Consulting Inc. Reportedly, the cores were taken from the Capay Dam in Yolo County, CA as part of a condition evaluation of the structure. Identification and descriptions of the samples and coring locations are outlined in Table 1. TABLE 1 SAMPLE IDENTIFICATION AND LOCATION DESCRIPTION FOR CORES FROM THE CAPAY DAM PROJECT Core ID Sampling Location Orientation in Structure C1 Apron slab near southern end of dam Vertical C7 Downstream face of dam Perpendicular to surface C8 Apron slab near middle of dam Vertical C17 Northern headgate structure, within rib element Horizontal Petrographic examination of the four core samples was requested to characterize the composition and condition of the concrete they represent. FINDINGS AND CONCLUSIONS Based on the findings of the petrographic examination, the body of concrete represented by the provided cores, excluding the exposed outer ends, is judged to be in fairly good condition (Figs. 7 through 10). Varying degrees of weathering and deterioration of the concrete is evident along the exposed outer surface of each of the four cores (Figs. 1 through 6). The cause of surface deterioration is uncertain, but may be related to one or more of the following: 1) impact or scouring with sediment in the water discharge, 2) damage related to cyclic freezing and thawing Main Office: 5400 Old Orchard Road Skokie, Illinois Phone: Fax: Mid-Atlantic Office: 9030 Red Branch Road, Suite 110 Columbia, Maryland Phone: Fax: New England Office: 1 Washington Street, Suite 300A Dover, New Hampshire Phone: Fax:

65 Stantec Consulting Inc. Page 2 of 18 CTLGroup Project No.: January 15, 2006 of the non-air-entrained concrete (provided the concrete is exposed to such conditions), and 3) long-term leaching and erosion from flowing and/or mildly aggressive water. Sparse surface-parallel hairline cracking is observed in the outer portions of a few cores. No evidence of significant alkali-silica reaction or other apparent causes of cracking in the body of concrete were apparent. Again, such damage could be related to cyclic freezing, if the structure is exposed to such conditions. Also, some localized damage is evident in areas of honeycombed concrete in the lower portion of Core C7 (Fig. 2). This honeycombed concrete exhibits evidence of apparent in-situ leaching and secondary deposits. Such poor consolidation of the concrete is not observed in the other cores. The following brief summaries of the existing condition and evidence of damage are based on results of the petrographic examination. Core C1 Apron slab near southern end of dam Core C1 is in fair to good condition (Fig. 7). The exposed outer surface is apparently spalled or otherwise lost, exposing a rough concrete surface that is partially covered with dried mud and/or deposits. The immediate surface exhibits locally soft paste, but depth of soft paste is shallow, less than 0.1 in. (2.5 mm). The core was received in two pieces, separate 7 to 7½ in. from the top end along what appears to be a pre-existing crack. A few hairline cracks are observed in the outer core segment, each extending parallel to the outer surface. These very tight cracks exhibit some secondary deposits. Otherwise, the remaining body of the concrete exhibits no visible crack, joints, or large entrapped air voids. The concrete appears to be well consolidated. Core C7 Downstream face of dam Core C7 is in mostly good condition, except for a band of honeycombed concrete 9 to 13 in. from the outer end (Fig. 8). The slanted exposed outer surface is apparently spalled or otherwise lost, exposing a rough concrete surface that is partially covered with dried mud and organic material (possibly algae or moss). The immediate surface exhibits locally soft paste, but depth of soft paste is shallow, less than 0.1 in. (2.5 mm). The core was received in two pieces, separate 12 to 13 in. from the top end along the honeycomb. Away from the honeycomb, the remaining body of the concrete appears to be well consolidated and exhibits no visible crack, joints, or large entrapped air voids.

66 Stantec Consulting Inc. Page 3 of 18 CTLGroup Project No.: January 15, 2006 Core C8 Apron slab near middle of dam The body of Core C8 is judged to be in good condition (Fig. 9). The exposed outer surface is apparently spalled or otherwise lost, similar to that observed in the other cores, exposing a rough concrete surface that is partially covered with dried mud and/or deposits. The immediate surface exhibits locally soft paste, but depth of soft paste is shallow, less than 0.1 in. (2.5 mm). The core was received in one intact piece. The body of the concrete appears to be well consolidated and exhibits no visible crack, joints, or large entrapped air voids. The core also contains a segment of steel reinforcing bar about 15 in. below the top end. The bar exhibits evidence of only slight corrosion. Core C17 Northern headgate structure The body of Core C17 is also judged to be in fairly good condition (Fig. 10). The exposed outer surface is spalled and deteriorated, similar to that observed in the other cores. Concrete in the upper approximately 3 to 4 in. of the core, however, is considerably weaker and more porous than in the remaining lower portion of the core. The findings of the examination suggest that the lesser quality of the near-surface concrete is likely related to under-consolidation of the concrete, higher water-cement ratio, and possibly excess water leaching. The body of the concrete below this weak upper region appears to be well consolidated and exhibits no visible crack, joints, or large entrapped air voids. Microscopical examination of the samples also revealed evidence of fairly extensive leaching of constituents, mainly calcium, from the cement paste binder throughout most of the depth of the cores. This is evident from examination of petrographic thin sections produced from various depths in the outer approximately 6 to 12 in. of each core that show very little to no crystals of portlandite (calcium hydroxide) in the paste (Figs. 11 and 12). Thin section examinations also found that hydration of the cement is advanced and essentially complete, as would be expected in a water-retention structure of such age. Leaching may be related to long-term movement of moisture through the concrete. Also, water retained by the dam should be further evaluated for its aggressivity. Soft and acidic water may promote excess leaching and erosion of concrete surface. With possible exception to softening and erosion of exposed concrete surfaces, no clearly apparent deleterious effects of the leaching were evident in the concrete samples. Such

67 Stantec Consulting Inc. Page 4 of 18 CTLGroup Project No.: January 15, 2006 leaching may reduce the ph of the concrete. However, based on staining tests using phindicator (phenolphthalein) solution on cross sections of the cores (Figs. 13 through 16) the ph appears to be above 10. These stain tests also show that the depth of carbonation in the cores is fairly shallow, given the age of the structure. The measured depths of carbonation in these cores are given in the following table: TABLE 1 DEPTHS OF CARBONATED CONCRETE IN CORES FROM THE CAPAY DAM PROJECT Core ID Sampling Location Depth of Carbonation, in. (mm) C1 Apron slab near southern end of dam 0.3 to 0.5 (7 to 13) C7 Downstream face of dam 0.5 to 1.0 (13 to 25) C8 Apron slab near middle of dam 0.12 to 0.20 (3 to 5) C17 Northern headgate structure 4.0 to 4.3 (101 to 110) Also, the structure reportedly has little steel reinforcement, so the consequences of reduced ph may not be significant. Long-term leaching could also affect the compressive strength of the concrete. Results of compressive strength testing are given elsewhere in this report. Concrete along the exposed outer surfaces does exhibit some limited softening in the cement paste. Depth of soft paste in Cores C1, C7, and C8 is shallow and generally less than 0.2 in. The outer approximately 4 in. of Core C17 is comparatively softer than at greater depth, but this is more likely due to issues related to consolidation and bleeding, rather that effects from weathering. The composition of the concrete represented by the cores is fairly consistent, with differences mainly in aggregate gradation and top size, and possibly water-cement ratio. The following additional findings are based on the results of the petrographic examination of the submitted core samples.

68 Stantec Consulting Inc. Page 5 of 18 CTLGroup Project No.: January 15, Concrete represented by each of the sample consists of natural gravel coarse aggregate, and natural, siliceous sand fine aggregate dispersed in a non-air-entrained, hardened paste of portland cement. No fly ash or other supplementary cementing materials were observed in the paste. 2. Air content in the concrete samples are generally low and estimated at less than 2%, except for the aforementioned band of poorly consolidated (honeycombed) concrete in Core C7. The concrete is not air entrained, based on the scarcity of small, spherical voids (less than 1 mm) in the paste. 3. Coarse and fine aggregates used in the concrete are predominantly hard and firm and judged to be of good quality. The concrete samples do not evidence of damage related to deleterious reactions between the aggregate and paste constituents, such as alkali-silica reaction. 4. Aggregate used in the concrete appears to be fairly well graded, however, some visible differences in gradation were noted between cores. The top size of the aggregate is also variable but apparently larger than 1 in. Aggregate particles 1 to 3 in. across are common and an aggregate particle larger than 3 in. is present at the inner end of Core C7. Such large aggregate is common in many dam structures. 5. Observed paste properties are consistent with a concrete made with a moderate to moderately high water-cement ratio (w/c). However, w/c was difficult to interpret due to the age of the structure, near complete hydration of the cement paste, and the apparent leaching of the cement paste. The light beige to light gray paste is moderately hard to moderately soft, fairly absorptive, and exhibits a dull luster. Fairly low percentages of residual (unhydrated) cement clinker particles remain in the paste. METHODS OF TESTS Petrographic examination of the concrete samples was performed in general accordance with ASTM C , "Standard Practice for Petrographic Examination of Hardened Concrete." Each core was examined, as received, using a stereomicroscope at magnifications up to 45X to study the general condition of the concrete. Each core was cut longitudinally into two halves and one of the resulting surfaces of each slice was lapped and examined using the stereomicroscope. Surfaces of freshly broken concrete were also studied with the

69 Stantec Consulting Inc. Page 6 of 18 CTLGroup Project No.: January 15, 2006 stereomicroscope. Small rectangular blocks were cut from another portion of each sample and one side of each block was vacuum impregnated with epoxy. After the epoxy set and hardened, each block was lapped, dried, and attached to a separate glass microscope slide with epoxy. The mounted specimens were reduced to a thickness of 20 to 30 µm ( to in.) and each of the resulting thin sections were examined using a polarized-light microscope at magnifications up to 400X to study aggregate and paste mineralogy and microstructure. Depth and extent of paste carbonation was initially determined by the application of a ph indicator (phenolphthalein) solution to freshly fractured and saw-cut surfaces of the concrete. The solution imparts a deep magenta stain to high-ph, non-carbonated cementitious paste, but does not stain reduced-ph, carbonated paste. Extent of carbonation was also confirmed during microscopical examination of the thin section. Ronald D. Sturm Senior Microscopist Lead Petrographer Microscopy RDS Attachments N:\All Projects\32\ Capay Dam - Stantec\Petrography\ laboratory report.doc

70 Stantec Consulting Inc. Page 7 of 18 CTLGroup Project No.: January 15, a. Side view, top end placed to the left 1b. Top end Fig. 1 Side and top end views of Core C1, as received for examination.

71 Stantec Consulting Inc. Page 8 of 18 CTLGroup Project No.: January 15, a. 2b. Fig. 2 Opposite side views of Core C7, as received for examination, top end placed to the left.

72 Stantec Consulting Inc. Page 9 of 18 CTLGroup Project No.: January 15, 2006 Fig. 3 Top end of Core C7, as received for examination. Note the plant material and paint on the deteriorated concrete surface. Steel reinforcing bar Fig. 4 Side view of Core C8, as received for examination, top end placed to the left. Note the location of a steel reinforcing bar embedded in the core.

73 Stantec Consulting Inc. Page 10 of 18 CTLGroup Project No.: January 15, a. Top end 5b. Bottom end Fig. 5 Top and bottom ends of Core C8, as received for examination. Note the paint on the deteriorated top surface.

74 Stantec Consulting Inc. Page 11 of 18 CTLGroup Project No.: January 15, 2006 Rough and porous concrete 6a. Side view 6b. Top end Fig. 6 Side and top end views of Core C17, as received for examination. Note the rough and porous appearance of the concrete in the upper portion of the core (left portion in 6a) and deterioration of the top surface (6b).

75 Stantec Consulting Inc. Page 12 of 18 CTLGroup Project No.: January 15, 2006 Cracks Fig. 7 Lapped cross section of Core C1 showing the general appearance and condition of the concrete. Damage includes deterioration of the top surface (Left) and some horizontal cracking). Scale is marked in inches. Honeycomb Fig. 8 Lapped cross section of Core C7 showing the general appearance and condition of the concrete. Note the isolated region of poorly consolidated concrete (honeycomb) near the inner end. Scale is marked in inches.

76 Stantec Consulting Inc. Page 13 of 18 CTLGroup Project No.: January 15, 2006 Fig. 9 Lapped cross section of Core C8 showing the general appearance and condition of the concrete. Scale is marked in inches. Fig. 10 Lapped cross section of Core C17 showing the general appearance and condition of the concrete. Scale is marked in inches.

77 Stantec Consulting Inc. Page 14 of 18 CTLGroup Project No.: January 15, a. Plane-polarized light. Sand grain Sand grain Cement paste 11b. Same field viewed with cross-polarized light. Fig. 11 Transmitted-light photomicrographs showing a representative portion of Core C1 at 6 in. depth in thin section. Note the lack of calcium hydroxide and other crystalline material in the cement paste, due to leaching. Examples of large cement clinker relics are marked with arrows. Length of field is 0.75 mm (0.03 in.).

78 Stantec Consulting Inc. Page 15 of 18 CTLGroup Project No.: January 15, 2006 Void 12a. Plane-polarized light. Sand grain Calcium hydroxide Sand grain Void Cement paste 12b. Same field viewed with cross-polarized light. Fig. 12 Transmitted-light photomicrographs showing a representative portion of Core C17 at 6 in. depth in thin section. Note the scarcity of calcium hydroxide and other crystalline material in the cement paste, due to leaching. Example of large cement clinker relics are marked with arrow. Length of field is 0.75 mm (0.03 in.).

79 Stantec Consulting Inc. Page 16 of 18 CTLGroup Project No.: January 15, a. Outer portion. 13b. Full core length. Fig. 13 Stained cross section of Core C1 showing the depth of carbonation. The surface was treated with a ph indicator (phenolphthalein) solution that imparts a magenta stain to highph, non-carbonated paste, but does not stain carbonated paste.

80 Stantec Consulting Inc. Page 17 of 18 CTLGroup Project No.: January 15, a. Outer portion. 14b. Full core length. Fig. 14 Stained cross section of Core C7 showing the depth of carbonation. The surface was treated with a ph indicator (phenolphthalein) solution that imparts a magenta stain to highph, non-carbonated paste, but does not stain carbonated paste.

81 Stantec Consulting Inc. Page 18 of 18 CTLGroup Project No.: January 15, 2006 Fig. 15 Stained cross section of Core C8 showing the shallow depth of carbonation along the exterior surface. Fig. 16 Stained cross section of Core C17 showing fairly deep carbonation of the poorly consolidated outer end.