senior principal engineer vulcan materials...

AMEC Geomatrix, Inc. 510 Superior Avenue, Suite 200 Newport Beach, CA USA 92663-3627 Tel (949) 642-0245 Fax (949) 642-4474 www.amecgeomatrixinc.com

April 11, 2011

Project 10168.011.3

Mr. Larry Lao Senior Principal Engineer Vulcan Materials Company 3200 San Fernando Road Los Angeles, CA 90065

Re: Responses to City of Irwindale Review Comments (dated March 21, 2011) Slope Stability Evaluation for North Slope & Duarte Fault for Reliance I Quarry Reliance One-Reclamation Plan, Vulcan Materials Company Irwindale, California CA Mine ID #91-19-0016

Dear Mr. Lao:

This letter presents responses by AMEC Geomatrix (AMEC) to review comments by Geologic Associates (GLA) on behalf of the City of Irwindale (the City) regarding AMEC’s response letter dated February 17, 2011 and entitled, “Responses to City of Irwindale Review Comments dated December 14, 2010, Slope Stability Evaluation for North Slope and Duarte Fault for Reliance I Quarry, Irwindale, California.” The review document is dated March 21, 2011 and bears the following title:

• Geotechnical Review, AMEC Response to GeoLogic Associates Technical Review, Document Dated February 17, 2011, Slope Stability for North Slope and Duarte Fault, Reliance I Quarry, Irwindale, California.

For completeness, a copy of the GLA’s review document, as transmitted to Vulcan by the City, is included in Appendix A. For clarity and easy reference, we reiterate below each review comment followed by our response. However, no response is provided to comments indicating that our previous responses were adequate or satisfactory.

GLA’s Comment 1 The response adequately addresses Comment No. 1.

GLA’s Comment 2 GLA agrees with the response that a site-specific ground motion hazard analysis was performed for the Reliance I Quarry using the NGA relations, site-specific shear wave velocity data, and the requirements of the 2007 CBC. The site-specific design spectrum is presented as the right-most column in Table 1 and on Figure B-1.

The last sentence of the response, however, is confusing. This sentence appears to imply that the peak ground acceleration (PGA) as determined by the 2007 CBC is equal to 2/3 of the site-specific MCE response spectrum (not the site-specific design spectrum), or 0.56 g. While 2/3 of the site-specific MCE response spectrum is, in fact, 0.59 g (= 2/3 x 0.88 g), the PGA

Mr. Larry Lao Vulcan Materials Company April 11, 2011

P:\10168.000.0\10168.011.3\April 2011 Response\Response_04.11.11.docx

as determined by the 2007 CBC is equal to 0.66 g per the aforementioned site-specific design spectrum as shown in Table 1 and on Figure B-I. This result (0.66 g) is higher than 2/3 of the site-specific MCE response spectrum (0.59 g) because it reflects the 80-percent minimum of the ASCE 7-05 Section 11.4.5 spectrum (= 0.80 x 0.82) per Section 21.3. The response doesn't make clear how or if a PGA of 0.56 may have been used in the analyses.

Response to Comment 2: In the February 17, 2011 response, we provided various PGA values. These values were provided for information only, and none of them was used in the analyses. The last sentence provided a PGA of 0.56 g, which was calculated from SDS/2.5, where SDS =1.41 g determined from the site-specific design spectrum, which in turn was based on the site-specific procedure.

GLA’s Comment 3 The response presents new/revised Newmark displacement analyses for Cross Sections A-A', B-B', and D-D'. Response spectra at locations behind the slope crest for eight acceleration time histories are compared with the site-specific response spectrum from Figure B-1. While the modeled time history spectra appear to have some correspondence with the site-specific response spectrum, the figures are too small with too many similarly colored lines to be able to accurately assess the degree of this correspondence. In particular, it appears that the low-period modeled time history spectra are generally below site-specific response spectrum, but the figure is too small to assess the significance of this potential unconservatism. GLA suggests that larger figures, perhaps with a logarithmic period scale and a line representing the average response of the eight time histories, be presented to allow a clearer assessment of the modeled vs. design spectra. Also, it appears as though deformation results from the worst-case time history are conservatively reported for each cross section rather than the more-commonly used metric of the average deformation calculated from all of the time histories.

The response says that Newmark sliding block analyses were revised based on the updated seismic response analyses, and acceleration time histories of the sliding blocks are presented. The response does not explain whether these time histories are of horizontal equivalent acceleration (shear stress along base of slide surface at each time step divided by slide mass), which would be in conformance with the ISSC Slope Stability Guidelines, or some kind of average acceleration per time step for the slide mass, which might not be in conformance. Note that AMEC's original 10/29/2010 report refers to these as "earthquake-induced seismic coefficient (k) time histories" without saying how they were derived. Based on the response text, tables, and figures, it appears as though the site response and slope stability/Newmark analyses were performed independently rather than as a paired analysis wherein stresses at the base of any given slide mass at each time step are passed from the site response program/module to the slope stability/Newmark module. If these analyses were not paired as described herein, but are rather the result of comparing a yield acceleration from a single pseudo-static slope stability analysis with a single acceleration time history, the search



for deformation-critical slide surfaces is subject to being incomplete and potentially unconservative (since the deformation-slide mass search space may not be fully explored). Were deformation analyses performed for a variety of potential failure masses? Note that a comparison of the pseudo-static slide mass for Cross Section B-B' with that of the FE site response analysis shows that the latter is about 10% thicker (137' vs. 125' as measured vertically from the mid-slope bench), which suggests that the FE-derived horizontal equivalent acceleration or "seismic coefficient time histories" used in the Newmark analyses may not be appropriate for the pseudo-static yield acceleration selected. GLA didn't perform this comparison for other cross sections.

Response to Comment 3: Figures B-6 through B-8 have been revised with a logarithmic period scale to show average response spectra at tops of the slopes of the eight time histories. Although for periods less than approximately 0.15 second, computed response spectra appear generally lower than site-specific response spectrum, it is not a sign of unconservatism. In fact, there is a portion of the computed average response spectrum that lies above the site-specific spectrum, and this indicates some degree of conservatism. This portion corresponds to the range of frequencies of interest that is most important to the slopes due to the fact that modes of vibration in this range have the largest modal participation factor. The frequencies of interest are between the fundamental period of the model (T1) and the predominant period of the input motion (T2). Shorter periods are for higher modes with small participation factors and little significance. For the project, T1 is approximately 1.15 seconds, and T2 is approximately 0.15 seconds. Figures B-6 through B-8 show reasonable comparison at periods T1 and T2 and conservatism between T1 and T2. Furthermore, the differences shown on Figures B-6 through B-8 can be expected due to the fact that QUAD4MU uses Rayleigh damping and a two-frequency scheme to provide damping values that have minimum variations over the range of frequencies of interest. In QUAD4MU, one frequency is chosen at the fundamental period (i.e., at T1) and the second frequency is chosen close to T2. As is the case with all procedures that utilize Rayleigh damping and a two-frequency scheme, frequencies between T1 and T2 will be under-damped and outside that range (e.g., periods less than 0.15 second) will be over-damped. There are other factors including basin and topographical effects contributing to the difference shown on Figures B-6 through B-8. The site-specific spectrum is for free-field conditions with soil strata overlying a rock half-space. The elevation of top of rock in the cross sections varies with distance, which is different from the case of rock half-space, resulting in basin effect (Bard and Gariel 1986). The topographic effects of the slope will also affect the response at top (Jibson 1987).

Deformation results from all time histories including the worst-case were reported for each cross section in our October 29, 2010 report and February 17, 2011 response. All of the results show seismic deformations less than 2 cm. Therefore, it was not deemed necessary to report an average value. Certainly, interested parties may use reported results to easily calculate the average value if necessary.



In the context of Newmark sliding block analysis, seismic coefficient, average acceleration, and horizontal equivalent acceleration of the sliding block all have the same physical meaning and are expressed as a fraction of gravity. These terms have been used widely in literature, and the derivation can be found easily (e.g. Kramer 1996, Bray et al. 1998). Therefore, the need to provide a definition and derivation in the project report did not seem critical. Nonetheless, to address the reviewer’s concerns, clarifications are provided herein. These time histories are obtained by dividing a resultant force time history by the mass of the soil above the potential failure surface, where the resultant force time history is the horizontal component of the dynamic stresses history acting on the potential failure surface integrated over the failure surface. In short, the histories obtained are in conformance with the ISSC Slope Stability Guideline.

The analyses were paired. Site response analyses were performed to obtain dynamic stresses in the model. As discussed in the above paragraph, the horizontal component of the dynamic stresses along the base of the critical slide mass were integrated over the slip surface and divided by the mass of the sliding block to derive average acceleration time history of the sliding block. Pseudo-static stability analyses were performed to obtain several critical slip surfaces for deformation analysis, and only the most critical surfaces were presented in the October 29, 2010 report and the February 17, 2011 response.

The FE site response analysis cross sections presented in the February 17, 2011 response were for a different critical slip surface. The FE sections corresponding to the pseudo-static stability analysis sections presented in the February 17, 2011 response are provided in this response (Figures B-3 through B-5 in Appendix B).


GLA’s Comment 5 The response adequately addresses Comment No. 5. For consideration, question marks used in geologic maps and cross sections symbols imply uncertainty (Compton, 1962).

GLA’s Comment 6 The consultant's revised figures reflect supplemental analyses. The revised geologic interpretations are supported by the data. The addition of cross section D-D' aids in clarifying site unit distribution.

Please comment on the depth to bedrock noted on Seismic Line 3. Alluvium or bedrock is identified at a depth of approximately 520-530 feet, however, the depth to bedrock indicated on Section B-B' is at approximately 490 feet. Although a shallower bedrock surface may be supported by the seismic line, it would result in a significant step up along Section B-B', which in turn would be observed in Sections C-C' and D-D'.



Please clarify the meaning and purpose of the "Fault Scarp in Bedrock" feature illustrated on Figure C-IA.

Please indicate where the parenthetic closure is for the USGS reference (page 7, paragraph 2, line 5 of the review response).

Please correct the designation indicated as LL-2 or provide information on this designation as a separate mapped unit (page 7, paragraph 4, line 2 of the review response).

Response to Comment 6: Our interpretation of the alluvium-bedrock contact for Seismic Line #3 suggests the contact could lie between depths of about 520 to 800 feet below the bottom of the quarry. However, considering the interpretive nature of the data, and potential impact on the overall stability of the proposed slopes relative to the elevation of the top of the siltstone bedrock, we have purposely selected to use the most conservative estimate as to the elevation of the alluvium-bedrock contact for use in our slope stability analyses. This depth-to-bedrock model is consistent for geologic cross sections B-B’, C-C’ and D-D’.

The term “Bedrock Fault Scarp” on Figure C-1A is meant to depict what we have interpreted to be a reflection of the 140- to 170-foot high, nearly vertical fault scarp along Seismic Line # 1 that sub parallels and passes through an approximately 500-foot long portion of the Duarte fault where the bedrock is juxtaposed with alluvium. Given this spatial positioning, along with the nature of the reflection data along this section of the seismic line, we have interpreted what would be a “window” of the bedrock in the hanging wall and exposed in the face of the fault scarp. Whether or not this interpretation is completely correct, it has little to no bearing on the stability of the proposed final slope along the north wall of the quarry.

The closing parenthesis is obviously on line 6 after the website link. This is simply due to the fact that the word processing software used treats the link as one word and will not break the string to fill in the gap left on line 5, thereby leaving this wide gap at the end of line 5).

LL-2 is a typographical error and should read LU-2.



GLA’s Comment 9 It is agreed that the available data for pits in the City of Irwindale suggest that higher strengths than those given in the ISSC Guidelines apply at Reliance 1. It would be beneficial to



demonstrate the effect of a modest increase in the assumed shear strength for the alluvium on the Factor of Safety for the "Results from Seepage Analysis" for Section D-D'. Additionally, it is noted that the required minimum Factor of Safety for static analysis is 1.5.

Response to Comment 9: We performed additional analyses for cross sections A-A’ and D-D’ to demonstrate the effect of an increase in the assumed shear strength for the alluvium on the Factor of Safety for the "Results from Seepage Analysis". Results of the analyses are included in Appendix B in this response. As expected, an increase of only 2 percent resulted in static factors of safety greater than 1.5.

GLA’s Comment 10 In general, the consultant's response adequately addresses Comment No. 10. The results of supplementary seepage analyses presented for cases where the fault is modeled with a series of permeable zones provide groundwater surfaces that are considered to be reasonable alternatives to the cascading model. This acknowledgement of the consultant's response is made, however, in the absence of specific geology and stratigraphy for the area north of the interpreted fault location. Additionally, groundwater levels within the pit when the 531-foot groundwater elevation was measured at V10AMMW4 are not documented or substantiated. Finally, data from wells RL-09-01 and RL-09-02, and other wells on-site were not included on the contour plots presented in Appendix F; it is recommended these data be incorporated in the plots in Appendix F.

Calculated site stability for the planned grades will be affected by groundwater levels. A program of long-term monitoring should be developed and incorporated into the project plans and specifications. The program should be implemented sufficiently in advance of the proposed deepening of the pit to allow design groundwater assumptions to be verified. Of particular relevance is the area in the immediate vicinity of the Duarte fault mapped by the consultant. Provisions should be made for monitoring groundwater adjacent to the fault, both up- and down-gradient.

It is presumed that the word "foot", which occurs at three locations on page 11 of the review response, is a misprint. Please confirm or clarify the wording. The consultant is referred to: paragraph 2, line 11, and paragraph 3, lines 8 and 12. Also, please note the typographical error on line 12 (vertical).

Response to Comment No. 10: Although there is no current groundwater level data available north of the Duarte fault, our hydrogeologic model has utilized the approximately 10 years of groundwater level records between 1988 and 1998 for the nearby Cyanamid & Owl well group that is located as close as about 380 feet from Vulcan Materials’ northern property boundary. During this 10-year period, there were two separate times where the highest groundwater level recorded was elevation 531



feet msl. Based on the character of other groundwater level data north of the Reliance quarry, it is our professional judgment that the Cyanamid & Owl group groundwater elevation of 531 feet msl represents the maximum probable high groundwater level in the vicinity closest to the Reliance quarry. Furthermore, in our opinion this elevated water level represents a “worst case” scenario and was therefore utilized in our slope stability models.

Regarding the exclusion of two of the wells, RL-09-01 and RL-09-02, associated with development of the local groundwater gradient maps, we offer the following explanation. First, well RL-09-01 is situated on the north side of a prominent groundwater barrier, namely the Duarte fault. It is our opinion that incorporation of the groundwater level data from this well into our model would skew the results and thereby yield an erroneous result. In the case of well RL-09-02, this well is not only located far afield of the other wells, but the groundwater level in this well is likely to be strongly influenced by the Duarte fault, which lies about 75 feet to the north. Moreover, as can be seen from the Main San Gabriel Basin Watermaster Groundwater Contour Maps for the San Gabriel Basin included in Appendix F of our response, the groundwater flow direction in the vicinity of this corner of the quarry is predominantly from east to west.

With respect to long-term monitoring of groundwater levels, the exploratory borings that were drilled and completed as monitoring wells were located to best produce the needed geologic and hydrologic data necessary for further analysis of the North Slope. They were not located or constructed to become long term monitoring wells and will therefore be backfilled and closed by Vulcan in the future to accommodate ongoing and future mining operations. However, Vulcan will continue monitoring these wells until such time that mining operations necessitate their removal.


GLA’s Comment 12 The response adequately addresses Comment No. 12. The assigned strength values were based on the consultant's research and judgment and appear to be reasonable for the material types. Please confirm whether or not the UCS of 500 psi referenced for the Topanga Formation was used in the stability analyses. If it was, please provide the appropriate documentation.

Response to Comment No. 12: No, the UCS of 500 psi was not used in the analyses.




GLA’s Comment 14 The response adequately addresses Comment No. 14. As a corroborating item, continued effort should be made to obtain and evaluate the offsite well records.

GLA’s Comment 15 There appears to be some inconsistencies remaining on the Revised Geologic Map (Figure 3), where LL-1, LL-2(?) and LL-3 are identified as covered by afi. Please verify that these units are either LU- units or a different set of units. If the latter case applies, please revise the legend accordingly. (It may also be of value for future reviewers to identify the individual layers on the stability and related analyses as Upper or Lower Alluvial Unit x rather than Upper or Lower Geologic Formation Layer x.)

Response to Comment No. 15: The “LL” unit designations should be “LU’, and have been revised accordingly on the geologic map.


GLA’s Comment 17 The consultant has provided a response to the bulleted items presented in the original review comment. The responses are based on the original data as well as a review of the supplemental analyses. Although the responses are not based on direct physical data, they do satisfy the intent of the original review comments.






ADDITIONAL REVIEW COMMENTS Additional review comments and/or items for approval include:

GLA Comment No. A1 The consultant should acknowledge a review memorandum issued by GLA on December 29, 2010 that was entitled “Groundwater Modeling for Reliance I North Slope, Irwindale, California.”

Response to Comment No. A1: AMEC reviewed the referenced memorandum and took that into account in our February 17, 2011 response.

GLA Comment No. A2 As agreed, the Consultant is to prepare a chronological summary of the design process giving a list of applicable documents and noting their relevance.

Response to Comment No. A2: It is agreed that this project has undergone a significant number of cycles of reviews and analyses. Therefore, a chronological summary will help to clarify the process and enable a reviewer to follow the evolution of the geotechnical analysis process for the project.

A thorough summary was already prepared and presented in the Background section of AMEC’s October 29, 2010 report. We have built on this information and have prepared a chronological summary of the various studies in table format (Table C-1) included in Appendix C of this response document.

GLA Comment No. A3 Figure 7 has been revised to include: a southerly sloping bedrock surface; fault planes projecting up into the alluvium; and revised groundwater surfaces. The inset map shows the approximate section location (Section A-A'). Comparing the inset map with a USGS topographic map, it appears that the section is located about 7,000 feet east of the quarry. Is the section shown on Figure 7 intended to be a more regional extension of Section A-A' included in the report as Figure 4? If so, please explain the bedrock elevation differences between Figures 4 and 7 in the vicinity of the quarry and the differences in groundwater elevations.

Response to Comment No. A3: The figure was meant to serve, as the title implies, as a “generalized cross section.” However, for more clarity we have replaced the inset map with a portion of the USGS Azusa and Baldwin Park 7.5’ Quadrangle, which depicts the location of cross section A-A’ transecting the Reliance quarry.


If you have questions regarding the content of this letter, please do not hesitate to contact the undersigned .

Sincerely yours, AMEC Geomatrix, Inc.

~--0. Scott Magorien Certified Engineering Geologist

P:\10168.000.0\10168.011 .3\April 2011 Response\Response_04.11.11 .docx

e ver ident and

Principal Geotechnical Engineer



Enclosures: Figure 3 - Revised Geologic Map (New Revision) Figure 7 - Revised Generalized Cross-Section through Duarte Fault Zone (New Revision) Appendix A - Copy of GeoLogic’s March 21, 2011 Review Comments Appendix B - Newmark Sliding Block Analyses, Site Seismic Response, and Slope Stability

Analyses Appendix C - Chronological Summary of Project Analyses and Reviews to Date

FIGURES

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150 ~~:::~~0~11111111111111111111-150 Approximate Scale in Feet

BaBe map . 511812 modified from V 007 with 1011611998 uk::an Materials Co ' 812311999 & 5f1112~b~· Combined Botto COlf1JOSit& d ta m Topography·

Slope Stability ~~~~~~D GEOLOGIC M~:octnbec2s,2ooii ion For North SI Relia~~~R Oeliance I Qua~pe & Duarte Fault ne-Recl

Vulcan Mate . I amation Plan

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By: jbd Project No. 10168.011.3 AME ate: 04/08/11

C Geomatrix Figure 3

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Area of Potential Cascading and/or Wedge-Shaped Groundwater Gradient

Lower Duarte Fault ----~oo~~u~~adle~=~ooTtlft-

Explanation - Cross Section

Fault, U = upthrown side; D -downthrown side

Conceptual elevation of water table, high water-level condition

Approximate Location of Upper Duarte Fault

Explanation - Location Map

Location of cross section line

0 2500 5000

Approximate scale in feet

A'

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1. Modified from Geomatrix Consultants, Inc. 2006, Addendum to Comprehensive Groundwater Modeling Report, Baldwin Park Operable Unit of the San Gabriel Valley, Superfund Site, Los Angeles County, California" September 8, 2006, prepared for Baldwin Park Operable Unit Cooperating Respondents.

Conceptual elevation of water ~. table, low water-level condition 2. Location inset map base map modified from U.S.G.S. 7.5 minute quadrangle maps

Approximate vertical scale

In feet

300

150

300 600

0 Approximate scele in feet

(:1: 50 feet)

REVISED GENERALIZED CROSS SECTION THROUGH DUARTE FAULT ZONE

Slope Stability Evaluation For North Slope & Duarte Fault For Reliance I Quarry

Reliance One-Reclamation Plan Vulcan Materials Company

Irwindale, California B: 'rw Date: 04/11/11 Pro'ect No. 10168.011.3

AM EC Geomatrix Figure 7 :2 Azusa 1995, California, and Baldwin Park 1966, photo-revised 1981. ~--.....~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~---~~~~~~~~~~~~~,__~~~~~~--'

APPENDIX A

Copy of GeoLogic’s March 21, 2011 Review Comments

IRWINDALE

CITY OF IRWINDALE PUBLIC WORKS DEPARTMENT

MINING AND RECLAMATION UNIT 5050 N. IRWINDALE AVENUE• IRWINDALE, CALIFORNIA 91706

PHONE 626/430-2210 • FAX 626/430-2295

LETTER OF TRANSMITTAL To: Larry Lao Date: March 22, 2011

No. of Copy

1

Vulcan Materials Company 3200 San Fernando Road Los Angeles, CA 91706

Description GEOTECHNICAL REVIEW AMEC RESPONSE TO GEO~LOGIC ASSOCIATES REVIEW DOCUMENT DATED FEBRUARY 17, 20ll SLOPE STABILITY EV ALU A TI ON FOR NORTH SLOPE AND DUARTE FAULT I<'OR RELIANCE 1 QUARRY IRWINDALE. CALII<'ORNIA

The above are submitted:

At your request (XX)

For your approval ( )

For your review ( )

For your use

For your files

(XX)

( )

For your information ( )

Comments : Please review and address City's comments on AMEC's Letter Report dated 12/17/11. Let me know if you have any questions.

Transmitted By: Kwok Tam ~~~~~~~~~~~~~~~~~~~~~~

Geologic Associates Geologists, Hydrogeologists and Engineers

Mr.Kwok Tam City Engineer City of Irwindale 5050 North Irwindale Avenue Irwindale, California 91706

GEOTECHNICAL REVIEW

March 21, 2011 Project No. 2010-0094 (Phase 900)

AMEC RESPONSE TO GEO-LOGIC ASSOCIATES REVIEW DOCUMENT DATED FEBRUARY 17, 2011 SLOPE STABILITY EVALUATION FOR NORTH SLOPE AND DUARTE FAULT FOR RELIANCE I QUARRY IRWINDALE, CALIFORNIA

1.0 INTRODUCTION

Geo-Logic Associates (GLA) has reviewed the latest AMEC document prepared for the Reliance I Quarry:

AMEC Geomatrix, Inc. (2011). Responses to City of Irwindale Review Comments (dated 1211412010) Slope Evaluation for North Slope & Duarte Fault for Reliance I Quarry -Reliance One-Reclamation Plan, Vulcan Materials Company, Irwindale, California, CA Mine ID #91-19-0016: consultant document prepared for Vulcan Materials Company, 20 p., attachments (Project No. 10168.011.3; dated February 17, 2011).

AMEC's report was prepared in response to review comments presented in Geo-Logic Associates' (GLA) review letter dated December 14, 2010:

Geo-Logic Associates, (2010), Geotechnical Review, AMEC Report Dated October 29, 2010, Slope Stability Evaluation for North Slope and Duarte Fault for Reliance I Quarry, Irwindale, California: Consultant report prepared for the City of Irwindale, California, 7 p. (Project No. 2010-0094, Phase 900; dated December 14, 2010).

This review letter addresses AMEC's responses presented in the February 17, 2011 report. It follows from a meeting held at the City oflrwindale on March 14, 2011 to discuss the project and AMEC's referenced responses to the review comments. Representatives of Vulcan Materials Company, GLA and the City oflrwindale were in attendance at the meeting. GLA's review comments pertinent to AMEC's February 17, 2011 report and supplemental review items for response are presented in the following two sections.

3921-A E. La Palma Avenue, Anaheim, CA 92807 Phone: (714) 630-5855 Fax: (714) 630-5866

2.0 REVIEW OF AMEC's RESPONSE TO COMMENTS

Review comments in reference to AMEC's February 17, 2011 response follow. For brevity the review comments are presented without AMEC' s original response.

1. The response adequately addresses Comment No. l.

2. GLA agrees with the response that a site-specific ground motion hazard analysis was performed for the Reliance I Quarry using the NGA relations, site-specific shear wave velocity data, and the requirements of the 2007 CBC. The site-specific design spectrum is presented as the right-most column in Table 1 and on Figure B-1.

The last sentence of the response, however, is confusing. This sentence appears to imply that the peak ground acceleration (PGA) as determined by the 2007 CBC is equal to 213 of the site-specific MCE response spectrum (not the site-specific design spectrum), or 0.56 g. While 2/3 of the site-specific MCE response spectrum is, in fact, 0.59 g (= 213 x 0.88 g), the PGA as determined by the 2007 CBC is equal to 0.66 g per the aforementioned site-specific design spectrum as shown in Table 1 and on Figure B-1. This result (0.66 g) is higher than 2/3 of the site-specific MCE response spectrum (0.59 g) because it reflects the 80-percent minimum of the ASCE 7-05 Section 11.4.5 spectrum (= 0.80 x 0.82) per Section 21.3. The response doesn't make clear how or if a PGA of 0.56 may have been used in the analyses.

3. The response presents new/revised Newmark displacement analyses for Cross Sections A-A', B-B', and D-D'. Response spectra at locations behind the slope crest for eight acceleration time histories are compared with the site-specific response spectrum from Figure B-1. While the modeled time history spectra appear to have some correspondence with the site-specific response spectrum, the figures are too small with too many similarly colored lines to be able to accurately assess the degree of this correspondence. In particular, it appears that the low-period modeled time history spectra are generally below site-specific response spectrum, but the figure is too small to assess the significance of this potential unconservatism. GLA suggests that larger figures, perhaps with a logarithmic period scale and a line representing the average response of the eight time histories, be presented to allow a clearer assessment of the modeled vs. design spectra. Also, it appears as though deformation results from the worst-case time history are conservatively reported for each cross section rather than the more-commonly used metric of the average deformation calculated from all of the time histories.

The response says that Newmark sliding block analyses were revised based on the updated seismic response analyses, and acceleration time histories of the sliding blocks are presented. The response does not explain whether these time histories are of horizontal equivalent acceleration (shear stress along base of slide surface at each time step divided by slide mass), which would be in conformance with the /SSC Slope Stability Guidelines, or some kind of average acceleration per time step for the slide mass, which might not be in conformance. Note that AMEC's original 10/29/2010 report refers to these as "earthquake-induced seismic coefficient (k) time histories" without

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saying how they were derived. Based on the response text, tables, and figures, it appears as though the site response and slope stability/Newmark analyses were performed independently rather than as a paired analysis wherein stresses at the base of any given slide mass at each time step are passed from the site response program/module to the slope stability/Newmark module. If these analyses were not paired as described herein, but are rather the result of comparing a yield acceleration from a single pseudo-static slope stability analysis with a single acceleration time history, the search for deformationcritical slide surfaces is subject to being incomplete and potentially unconservative (since the deformation-slide mass search space may not be fully explored). Were deformation analyses performed for a variety of potential failure masses? Note that a comparison of the pseudo-static slide mass for Cross Section B-B' with that of the FE site response analysis shows that the latter is about 10% thicker (137' vs. 125' as measured vertically from the mid-slope bench), which suggests that the FE-derived horizontal equivalent acceleration or "seismic coefficient time histories" used in the Newmark analyses may not be appropriate for the pseudo-static yield acceleration selected. GLA didn't perform this comparison for other cross sections.

4. The response adequately addresses Comment No. 4.

5. The response adequately addresses Comment No. 5. For consideration, question marks used in geologic maps and cross sections symbols imply uncertainty (Compton, 1962).

6. The consultant's revised figures reflect supplemental analyses. The revised geologic interpretations are supported by the data. The addition of cross section D-D' aids in clarifying site unit distribution.

Please comment on the depth to bedrock noted on Seismic Line 3. Alluvium or bedrock is identified at a depth of approximately 520-530 feet, however, the depth to bedrock indicated on Section B-B' is at approximately 490 feet. Although a shallower bedrock surface may be supported by the seismic line, it would result in a significant step up along Section B-B', which in turn would be observed in Sections C-C' and D-D'.

Please clarify the meaning and purpose of the "Fault Scarp in Bedrock" feature illustrated on Figure C-1 A .

Please indicate where the parenthetic closure is for the USGS reference (page 7, paragraph 2, line 5 of the review response).

Please correct the designation indicated as LL-2 or provide information on this designation as a separate mapped unit (page 7, paragraph 4, line 2 of the review response).



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9. It is agreed that the available data for pits in the City of Irwindale suggest that higher strengths than those given in the !SSC Guidelines apply at Reliance 1. It would be beneficial to demonstrate the effect of a modest increase in the assumed shear strength for the alluvium on the Factor of Safety for the "Results from Seepage Analysis" for Section D-D'. Additionally, it is noted that the required minimum Factor of Safety for static analysis is 1.5.

10. In general, the consultant's response adequately addresses Comment No. 10. The results of supplementary seepage analyses presented for cases where the fault is modeled with a series of permeable zones provide groundwater surfaces that are considered to be reasonable alternatives to the cascading model. This acknowledgement of the consultant's response is made, however, in the absence of specific geology and stratigraphy for the area north of the interpreted fault location. Additionally, groundwater levels within the pit when the 531-foot groundwater elevation was measured at VIOAMMW4 are not documented or substantiated. Finally, data from wells RL-09-01 and RL-09-02, and other wells on-site were not included on the contour plots presented in Appendix F; it is recommended these data be incorporated in the plots in Appendix F.

Calculated site stability for the planned grades will be affected by groundwater levels. A program of long-term monitoring should be developed and incorporated into the project plans and specifications. The program should be implemented sufficiently in advance of the proposed deepening of the pit to allow design groundwater assumptions to be verified. Of particular relevance is the area in the immediate vicinity of the Duarte fault mapped by the consultant. Provisions should be made for monitoring groundwater adjacent to the fault, both up- and down-gradient.

It is presumed that the word "'foot", which occurs at three locations on page 11 of the review response, is a misprint. Please confirm or clarify the wording. The consultant is referred to: paragraph 2, line 11, and paragraph 3, lines 8 and 12. Also, please note the typographical error on line 12 (vertical).


12. The response adequately addresses Comment No. 12. The assigned strength values were based on the consultant· s research and judgment and appear to be reasonable for the material types. Please confirm whether or not the UCS of 500 psi referenced for the Topanga Formation was used in the stability analyses. If it was, please provide the appropriate documentation.


14. The response adequately addresses Comment No. 14. As a corroborating item, continued effort should be made to obtain and evaluate the offsite well records.

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15. There appears to be some inconsistencies remaining on the Revised Geologic Map (Figure 3), where LL-I, LL-2(?) and LL-3 are identified as covered by af;. Please verify that these units are either LU- units or a different set of units. If the latter case applies, please revise the legend accordingly. (It may also be of value for future reviewers to identify the individual layers on the stability and related analyses as Upper or Lower Alluvial Unit x rather than Upper or Lower Geologic Formation Layer x.)


17. The consultant has provided a response to the bulleted items presented in the original review comment. The responses are based on the original data as well as a review of the supplemental analyses. Although the responses are not based on direct physical data, they do satisfy the intent of the original review comments.




3.0 ADDITIONAL REVIEW COMMENTS

Additional review comments and/or items for approval include:

Comment No. Al: The consultant should acknowledge a review memorandum issued by GLA on December 29, 2010 that was entitled ''Groundwater Modeling for Reliance I North Slope, Irwindale, California".

Comment No. A2: As agreed, the Consultant is to prepare a chronological summary of the design process giving a list of applicable documents and noting their relevance.

Comment No. A3: Figure 7 has been revised to include: a southerly sloping bedrock surface; fault planes projecting up into the alluvium; and revised groundwater surfaces. The inset map shows the approximate section location (Section A-A'). Comparing the inset map with a USGS topographic map, it appears that the section is located about 7,000 feet east of the quarry. Is the section shown on Figure 7 intended to be a more regional extension of Section A-A' included in the report as Figure 4? If so, please explain the bedrock elevation differences between Figures 4 and 7 in the vicinity of the quarry and the differences in groundwater elevations.

4.0 CLOSURE

Provided the items presented above are addressed by the consultant, the project is considered acceptable from a geotechnical standpoint. GLA's services consist of providing technical advice to the City regarding geotechnical recommendations presented in the referenced report. The services were limited to review of documents provided by the City and the Project Geotechnical Consultant. The opinions, conclusions and recommendations are made in accordance with

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generally accepted principles and practices of the geotechnical profession. No other warranty, express or implied is made or intended by providing our services on this project.

This opportunity to be of service is appreciated. If you have any questions regarding the above, please call.

Geo-Logic Associates

David M. Luka Senior Engineering Geologist CEG 1767 (Expires July 31, 2011)

Robbie M. Warner Senior Geotechnical Engineer GE 2690 (Expires December 31, 2011)

Brian D. Constant Principal Engineer GE 2278 (Expires March 31, 2012)

Consultant to the City:

~~ Kent McMillan, Ph.D. CEG 1152 (Expires March 31, 2012) DML/RMW/BDC/KM/ljo

Attachment: None

Distribution: Mr. Kwok Tarn, Addressee (2)

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APPENDIX B

Newmark Sliding Block Analyses, Site Seismic Response, and Slope Stability Analyses

Figure B‐1. Figure B‐2.Fig

Notes: Critical slip surface Δ: Vertical fixed and horizontal free boundary

: Transmitting boundary O: Top of slope where acceleration time history is used to compute response spectrum for comparison with site‐specific response spectrum.

Figure B‐3. Newmark Analysis Mesh for Cross Section A‐A’.

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Figure B‐4. Newmark Analysis Mesh for Cross Section B‐B’.

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Figure B‐5. Newmark Analysis Mesh for Cross Section D‐D’.

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Figure B-6. Comparison of response spectra from site-specific ground motion hazard analysis and 2D

seismic site response analysis at top of section A-A’.


seismic site response analysis at top of section B-B’.

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Figure B-9. Static Stability Analysis for Cross Section A-A’ – Groundwater from Seepage Analysis.

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C:\projects\10168.011.3\AA-stability-highGW-2percent.gszMethod: SpencerPit water level at Ele. 295 feet

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①: Upper Geologic Formation , Unit Weight: 130, Shear/Normal Function: Upper unit②: Lower Geo Formation Layer 1 , Unit Weight: 130, Shear/Normal Function: Lower unit 1 ③: Lower Geo Formation Layer 2 , Unit Weight: 130, Shear/Normal Function: Lower unit 2 ④: Lower Geo Formation Layer 3 , Unit Weight: 130, Shear/Normal Function: Lower unit 3 ⑤: Lower Geo Formation Layer 4 , Unit Weight: 130, Shear/Normal Function: Lower unit 4 ⑥: Lower Geo Formation Layer 5 , Unit Weight: 130, Shear/Normal Function: Lower unit 5 ⑦: Lower Geologic Formation , Unit Weight: 130, Shear/Normal Function: Lower unit 6 ⑧: Duarte Fault , Unit Weight: 130, Cohesion: 100 psf, Phi: 25 °⑨: Highly weathered bedrock , Unit Weight: 130, Cohesion: 200 psf, Phi: 24 °⑩: Bedrock

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Strengths were increased by 2% for the alluvium

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Figure B-10. Static Stability Analysis for Cross Section D-D’ – Groundwater from Seepage Analysis.

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①: Upper Geologic Formation , Unit Weight: 130, Shear/Normal Function: Upper unit②: Lower Geo Formation Layer 1 , Unit Weight: 130, Shear/Normal Function: Lower unit 1 ③: Lower Geo Formation Layer 2 , Unit Weight: 130, Shear/Normal Function: Lower unit 2 ④: Lower Geo Formation Layer 3 , Unit Weight: 130, Shear/Normal Function: Lower unit 3 ⑤: Lower Geo Formation Layer 4 , Unit Weight: 130, Shear/Normal Function: Lower unit 4 ⑥: Lower Geo Formation Layer 5 , Unit Weight: 130, Shear/Normal Function: Lower unit 5 ⑦: Lower Geologic Formation , Unit Weight: 130, Shear/Normal Function: Lower unit 6 ⑧: Duarte Fault , Unit Weight: 130, Cohesion: 100 psf, Phi: 25 °⑨: Highly weathered bedrock , Unit Weight: 130, Cohesion: 200 psf, Phi: 24 °⑩: Bedrock

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APPENDIX C

Chronological Summary of Project Analyses and Reviews to Date

Preparation Date Document Title Author Reason for Preparation/Sysnopsis

August 9, 2005

Reliance Quarry Water-Level Evaluation Reliance Quarry, Vulcan Materials Company, Irwindale and Azusa, California, Project No.

8490.001.0

Geomatrix Consultants

Hydrogeologic study consisting of an evaluation of water levels in the vicinity of the Reliance Quarry.

August 15, 2005Slope Stability Evaluation for Extended Mining Depth, Reliance Pit, Irwindale,

California, Project No. 8490.001.0


Results of static and pseudostatic slope stabilty analyses for various mining slope configurations proposed by Vulcan.

September 28, 2007

Slope Stability Evaluation for Extended Mining Depth Reliance Quarry, Irwindale, California, Updated September 28, 2007,

Project 10168.011.0


This report addresses comments from the City of Irwindale regarding the 2005 report and updates analyses presented in the 2005 report. This report contained detailed slope displacement

analyses, site-specific analyses, seismic site response, and Newmark displacement analyses.

November 19, 2007Response to City of Irwindale Review

Comments, Supplement to Report dated September, 28, 2007, Project 10168.011.0


This report addresses comments (dated October 19 and 22, 2007) from the City of Irwindale regarding the updated September 28,

2007 report. It contains additional slope stability, Newmark analyses, and site-specific hazard analysis with spectrally-matched

time histories.

July 11, 2008Amended Reclamation Plan for the Reliance I Quarry and Reliance II Landfill, CA Mine ID #

91-19-0016

Department of Conservation, Office of Mine Reclamation

Review comments regarding Vulcan's proposed amended reclamation plan.

September 17, 2008

Response to Comments, Amended Reclamation Plan for the Reliance I Quarry

and Reliance II Landfill, CA Mine ID # 91-19-0016

Department of Conservation, Office of Mine Reclamation

Review comments regarding Vulcan's proposed amended reclamation plan: OMR required resolution of the following issues: a better definition of the Duarte fault, inclusion of likely nature of fault

materials; consideration of higher groundwater levels in slope stability models.

January 6, 2009

Response to State of California Department of Conservation’s Office of Mine Reclamation Review Comments, Slope Stability Evaluation

for Reliance I Quarry North Slope, Project 10168.011.3

AMEC Geomatrix, Inc.

Review of geologic and groundwater data; preparation and analysis of new hydrolgeolgic model.

CHRONOLOGICAL SUMMARY OF PROJECT ANALYSES AND REVIEWS TO DATESLOPE STABILITY EVALUATION FOR NORTH SLOPE & DUARTE FAULT FOR RELIANCE I QUARRY

Vulcan Materials CompanyCA Mine ID #91-19-0016

TABLE C-1

P:\10168.000.0\10168.011.3\April 2011 Response\chronology.xlsAMEC Geomatrix, Inc.

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TABLE C-1

April 29, 2009

Review of AMEC Geomatrix, Inc., 2009 Response to State of California Department

of Conservation's Office of Mine Reclamation Review Comments, Slope Stability Evaluation

for Reliance I Quarry North Slope

GeoLogic Associates Comments regarding AMEC's January 6, 2009 report.

July 15, 2009Stability Evaluation of North Slope, Reliance I

and Azusa-Reliance Quarries, Irwindale, California, Project 10168.011.3


Additional refinement of geologic/hydrologic model, and additional analyses.

July 30, 2009 Draft File Memorandum Kent McMillan, PhD, Consulting Geologist

Comments regarding AMEC's July 15, 2009 report; request for field exploration in support of model used in analyses.

October 29, 2010

Slope Stability Evaluation for North Slope & Duarte Fault for Reliance I Quarry Reliance

One-Reclamation Plan, Vulcan Materials Company, Project No. 10168.011.3


Evaluation performed to supplement previous studies at the subject site, and address review comments from the State of California

Department of Conservation’s Office of Mine Reclamation (OMR) on July 11, 2008 and September 17, 2008; presentation of field

exploration results, refinement and analysis of geologic/hydrogeologic model.

December 14, 2010

Geotechnical Review, AMEC Report Dated October 29, 2010, Slope Stability Evaluation for North Slope and Duarte Fault for Reliance

I Quarry, Irwindale, California

GeoLogic Associates Review comments regarding AMEC's October 29, 2010 report.

December 29, 2010 Memorandum - Groundwater Modeling for Reliance I North Slope, Irwindale, California GeoLogic Associates Review comments regarding AMEC's October 29, 2010 report and

recommendations for parametric studyof groundwater model.


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TABLE C-1

February 17, 2011

Responses to City of Irwindale Review Comments (dated December 14, 2010), Slope Stability Evaluation for North Slope & Duarte

Fault for Reliance I Quarry Reliance One-Reclamation Plan, Vulcan Materials Company, Project No. 10168.011.3


Presentation of additional analyses, refinement and analyses of geolgic model; refinement of groundwater models; additional

analyses.

March 21, 2011

Geotechnical Review, AMEC Response to GeoLogic Associates Review, Document Dated February 17, 2011, Slope Stability

Evaluation for North Slope and Duarte Fault for Reliance I Quarry, Irwindale, California

GeoLogic AssociatesAcceptance of most responses provided by AMEC in AMEC's

February 17, 2011 response document; request for clarification of a few issues.

April 11, 2011

Responses to City of Irwindale Review Comments (dated March 21, 2011), Slope

Stability Evaluation for North Slope & Duarte Fault for Reliance I Quarry Reliance One-

Reclamation Plan, Vulcan Materials Company, Irwindale, California, CA Mine ID

#91-19-0016

AMEC Geomatrix, Inc. Final Response Document.


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