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HomeMy WebLinkAboutDEV 2017-0229; VERSUM MATERIALS CHANNEL STABILIZATION; REPORT OF GEOTECHNICAL INVESTIGATION; 2017-07-26GROUP DELTA 1 1 /17/7 0 1~ C11 ;7 Versum Materials July 26, 2017 1969 Palomar Oaks Way FRZ L EO Si J~l1iL2_Proect No. SD535 Carlsbad, CA 92011 1 initia. Dbcumerht No. 17-0087 Attention: Mr. William Elkins P w1ED NOV 02 2017, SUBJECT: REPORT OF G EOTECHNICAL INVESTIGATION Versum Materials -Swale Repair 1969 Palomar Oaks Way ' Carlsbad, California 92011 Mr. Elkins: LAND DEVELOP MNT F N 7 We are pleased to submit the results of our geotechnical investigation for the swale repair on the Versum Materials property, located in Carlsbad, California. Our investigation was conducted in general accordance with our proposal (Proposal No. 17-008) dated February 7, 2017. The approximate location of the site is shown on the Site Location Map, Figure 1. The approximate locations of the four areas we sampled surficial soils are shown on Exploration Plan, Figure 2A. Pictures of the existing site conditions are shown in Figure 2B. 1.0 INTRODUCTION The purpose of our investigation was to characterize the general geotechnical constraints to site development, and provide preliminary geotechnical recommendations for the design of the proposed regrading and surfacing of the existing slope and swale. The recommendations provided herein are based on ourrecent field visit, laboratory tests, engineering and geologic analyses, as well as our previous experience with similar conditions. 1.1 Scope of Services This report was prepared in general accordance with the provisioris of the referenced proposal in Appendix A (GDC, 2017). In summary, we provided the following scope of services. An exploration of the site including four soil samples taken at the approximate locations shown on the Exploration Plan, Figure 2A. Laboratory testing of the soil samples including sieve analysis, expansion, R-Value, and corrosivity testing. The laboratory test results are presented in Appendix B. Report of Geotechnical Investigation Project No. 5D535 Swale Repair July 26, 2017 Versum Materials Page 2 . Engineering analysis of the field and laboratory data to help develop geotechnical recommendations for site preparation, remedial earthwork, and finish concrete design. Preparation of this report summarizing our findings, conclusions and preliminary geotechnical recommendations for site development. 1.2 Site Description The site is located to the south of the Versum Materials building located at 1969 Palomar Oaks Way in Carlsbad, Califonia, as shown in Figure 2A. The site conditions are documented in pictures shown in Figure 2B. The existing site consists of a concrete lined swale at the bottom of the drainage, and a dirt slope with low vegetation ranging in height from approximately five to ten feet up to the existing building grade (Photo 1). The slope inclination varies slightly, but averages about a 2:1 horizontal to vertical angle. Based on previous explorations (Geotechnics, 2010), the slope consists of fill soils. The fill is underlain by potentially compressible and liquefiable alluvial deposits. The drainage empties into a pond immediately to the west of the subject site (Photo 2). At the time of our field investigation, the slope had been eroded to various degrees (Photo 3) and standing water was observed in the bottom of the swale (Photo 4). 1.3 Proposed Development It is our understanding that the current proposed improvement plan is to regrade the existing slope, remove the existing concrete swale, and install a permanent surface to prevent future erosion. Based on communications with Joanne Tyler of O'Day Consultants, Cable Concrete by International Erosion Control Systems, or a comparable system, is planned to be used as the permanent resurfacing of the slope for erosion control. Cable Concrete uses precast concrete blocks joined together with steel cables and a geotextile fabric to form a mat that allows vegetation to grow through while water can infiltrate. 2.0 FIELD AND LABORATORY INVESTIGATION The field investigation included a visual and geologic reconnaissance of the site and the excavation of four test samples on June 27, 2017. The approximate locations of the excavations are shown on the Exploration Plan, Figure 2A. Bulk soil samples were collected from all four locations for geotechnical testing and analyses. The laboratory testing program included gradation analysis to aid in material classification using the Unified Soil Classification System (USCS); Expansion Index (El), R-Value, and corosivity testing were conducted on bulk samples to aid in site development recommendations. The laboratory test results are presented in Appendix B. A~ I3RDUP DELTA Report of Geotechnical Investigation Project No. SD535 Swale Repair July 26, 2017 Versum Materials Page 3 The soils sampled generally consist of silty sand (SM) and clayey sand (SC). The soils on the slope were sampled at locations H-i and H-3. The soils near the bottom of the slope at the existing concrete swale were sampled at H-2 and H-4. As shown in Appendix B, the soils have approximately 35% fines and a low expansion potential. The soils near the bottom of the swale were wet, and test results indicate they are severely corrosive to metals. 3.0 CONCLUSIONS The planned improvements appear to be feasible from a geotechnical perspective, provided that appropriate measures are implemented during construction. Several geotechnical conditions will need to be addressed: Slope erosion has created irregular and possibly unstable slope conditions. The planned improvements should incorporate regrading of the slope at an inclination no greater than 1'/:1 (horizontal:vertical) to rectify the existing conditions. Laboratory tests indicate that the near surface fill soils at the site primarily consist of silty sand (SM) and clayey sand (SC). Based on laboratory testing, these soils are anticipated to have a low expansion potential (20<El<50). Soils with a low expansion potential or greater (El>20) are typically not considered suitable fill for heave sensitive improvements. If a flexible surface improvement, such as Cable Concrete,or equivalent, is used and some heave and settlement are considered tolerable -factoring in both structural integrity and appearance of the surface improvements - low expansion material would be considered suitable subgrade material. Laboratory testing indicates that some of the onsite soils are severely corrosive to buried metals. A corrosion consultant may be contacted for specific recommendations. The presence of water runoff indicates that shallow groundwater may be encountered during site grading. During grading activities, exposed subgrade materials may be saturated, soft, or yielding. Recommendations for stabilizing subgrade are presented in the following section. AL.- GROUP DELTA S Report of Geotechnical Investigation Project No. SD535 Swale Repair July 26, 2017 Versum Materials Page 4 4.0 RECOMMENDATIONS The remainder of this report presents recommendations regarding earthwork construction and the design of the proposed improvements. These recommendations are based on empirical and analytical methods typical of the standards of practice in southern California. If these recommendations do not cover a specific feature of the project, contact our office for revisions. 4.1 Plan Review We recommend that the improvement plans be reviewed by Group Delta prior to construction. 4.2 Excavation and Grading Observation Remedial grading excavations should be observed by the geotechnical engineer of record. During grading, the geotechnical engineer should provide observation and testing services continuously. Such observations are considered essential to identify field conditions that differ from those anticipated by this investigation, to adjust designs to the actual field conditions, and to determine that the remedial grading is accomplished in general accordance with the recommendations presented in this report. 4.3 Earthwork Grading and earthwork should be conducted in general accordance with the applicable local grading ordinance and the requirements of the current California Building Code. The following recommendations are provided regarding specific aspects of the proposed earthwork construction. 4.3.1 Site Preparation General site preparation for any permanent improvements should begin with the removal of deleterious materials from the site. Deleterious materials include existing structures, foundations, pavements, slabs, trees, vegetation, trash, contaminated soil and other demolition debris. Existing subsurface utilities that will be abandoned should be removed and the excavations backfilled and compacted as described in the section titled Fill Compaction. Alternatively, the abandoned pipes may be grouted with a two-sack sand-cement slurry under the observation of the geotechnical consultant. A~ GROUP DELTA Report of Geotechnical Investigation Project No. 5D535 Swale Repair July 26, 2017 Versum Materials Page 5 4.3.2 Improvement Areas We understand that the planned improvements consist of regrading the existing slope and installing a permanent surface, such as Cable Concrete, to protect from future erosion. After site preparation, the existing slope should be regraded at an inclination not exceeding 11/2:1 (horizontal:vertical). Any soil affected by erosion, including soft, yielding soils should be removed to expose competent material approved by the geotechnical consultant. Approved fill material may then be placed as uniformly compacted fill to the planned finish subgrades. Fill soils should be placed on a horizontal subgrade to ensure proper compaction and bonding within the existing slope geometry. The contractor may achieve a level working surface by benching into the existing soils. A sketch of a typical benching operation is provided, for reference only, in Figure 3A. After removal of existing soil, the upper 12-inches of exposed material should then be scarified and brought to above optimum moisture content, and compacted as described in the section titled Fill Compaction. Fill soils should be placed in level, horizontal lifts, to above finish subgrade elevations. Compacted fill should then be cut to planned finish subgrade elevations with fine grading equipment. Based on laboratory testing, existing near-surface soils have low expansion potential and severe corrosion potential to buried metals. If surface improvements are not heave sensitive, such as the flexible Cable Concrete, and corrosion prevention measures are taken, the near-surface material is considered suitable to be re-used as compacted fill. During grading, the fill soils should be tested to verify the conditions. If surface improvements are susceptible to heave or corrosion, existing fill should be removed and replaced with imported material in the upper two feet of finish subgrade. Imported material should meet the criteria described in the section titled Fl/I Compaction below. If Cable Concrete is used, it should be placed per the manufacturers requirements and recommendations. Typical details are provided in Figure 3B. A typical concrete swale should be formed at the toe of the slope, sized for the appropriate flow volumes, and may incorporate the Cable Concrete detail shown in Figure 3B. An alternative to Cable Concrete would be a shotcrete facing on the graded slope. Typical shotcrete details are shown in Figure 3C, including necessary weep holes. To reduce the potential for cracking and spalling of the shotcrete, a minimum of two feet of material with an Expansion Index of 20 or less (El<20) is recommended beneath the shotcrete finish. Water can infiltrate GROUP DELTA S S Report of Geotechnical investigation Project No. SD535 Swale Repair July 26, 2017 Versum Materials Page 6 cracks and spalled sections and can lead to soil erosion and the undermining of the shotcrete itself. In either case, the surface improvements should be constructed immediately after compaction of the subgrade. If any erosion, drying, or other degradation occurs before installation of the surface improvements, the upper 12 inches of subgrade should be scarified immediately prior to the installation, brought to optimum moisture, and compacted as described in the section titled Fill Compaction. As discussed above, and in the referenced report (Geotechincs. 2010), the improvement area is situated over potentially compressible and liquefiable alluvium. It is our understanding that the slope and swale is a non-essential, non-hazardous, non-occupied structure, and that the risks associated with the potential for settlement due to liquefaction of the underlying alluvium are deemed tolerable by the owner. Furthermore, it is our understanding that the current loading conditions near the top of slope (within eight feet) will remain approximately the same. Consequently, the fill and underlying alluvium will not be subjected to substantial new loads, and should experience little settlement. 4.3.3 Fill Compaction All fill and backfill should be placed at slightly above optimum moisture content using equipment that is capable of producing a uniformly compacted product. The minimum recommended relative compaction is 90 percent of the maximum dry density based on ASTM D1557. Sufficient observation and testing should be performed by the geotechnical consultant so that an opinion can be rendered as to the compaction achieved. Rocks or concrete fragments greater than 6 inches in maximum dimension should not be used in structural fill. Due to possible shallow groundwater, saturated, soft, or otherwise yielding subgrade may be encountered that would not allow 90 percent relative compaction to be reasonably achieved through typical compaction efforts. If encountered, any standing water should be pumped out of the excavation. The excavation bottom should be leveled to a reasonable degree by removing soft mud. A geotextile fabric, such as Mirafi HP570, or equivalent, should be placed on the excavation bottom - and up the excavation sides if applicable. A 12 to 18-inch section of gravel (crushed rock) should be placed on top of the fabric to bridge the gap over the soft subgrade. A filter fabric should then be placed over the gravel section to prevent migration of fines into the void spaces over time. Compacted fill can then be placed over this section. This section should A&_ GROUP DELT( Report of Geotechnical Investigation Project No. SD535 Swale Repair July 26, 2017 Versum Materials Page 7 not be within 12 inches of the finish subgrade elevation. If necessary, the excavation should be deepened to account for the section. Imported fill sources should be observed prior to hauling onto the site to determine the suitability for use. In general, imported fill materials should consist of granular soil with less than 35 percent passing the No. 200 sieve based on ASTM C136 and an Expansion Index less than 20 based on ASTM D4829. Samples of the proposed import should be tested by the geotechnical consultant in order to evaluate the suitability of these soils for their proposed use, which may include corrosion testing. During grading operations, soil types may be encountered by the contractor that do not appear to conform to those discussed within this report. The geotechnical consultant should be notified to evaluate the suitability of these soils for their proposed use. A two-sack sand and cement slurry may also be used for structural fill as an alternative to compacted soil. It has been our experience that slurry is often useful in confined areas which may be difficult to accesswith typical compaction equipment. Samples of the slurry should be fabricated and tested for compressive strength during construction. A minimum 28-day compressive strength of 100 pounds per square inch (psi) is recommended for the two-sack sand and cement slurry. 4.3.4 Expansive Soils We anticipate that the proposed excavations will predominately generate mixtures of silty to clayey sand. Based on our laboratory testing, these materials have a low expansion potential based on common criteria (20<El<50). For heave sensitive improvements, we recommend the upper two feet of subgrade material have very low expansion potential (Ek20). 4.3.5 Reactive Soils In order to assess the sulfate exposure of concrete in contact with the site soils, samples were tested for water-soluble sulfate content, as shown in Figure B-2. The test results indicate that the on-site soils have a negligible potential for sulfate attack based on commonly accepted criteria. The sulfate content of the finish subgrade soils should be determined during fine grading. In order to assess the reactivity of the site soils with buried metals, the pH, resistivity, and chloride contents were also determined (see Figure B-2). Resistivity tests suggest that the on-site soils are very corrosive to ferrous metals. Chloride content was elevated in the sample that had been saturated by water runoff and suggests that these soils are severely corrosive to metals. Typical corrosion control measures should be incorporated into design, such as providing A&I ERDUP DELTA Report of Geotechnical Investigation Project No. SD535 Swale Repair July 26, 2017 Versum Materials Page 8 minimum clearances between reinforcing steel and soil, or sacrificial anodes for buried metal structures. A corrosion consultant may be contacted for specific recommendations. 4.3.6 Temporary Excavations Temporary excavations are anticipated for the re-grading of the proposed slope. All excavations should conform to Cal-OSHA guidelines. Temporary slopes should be inclined no steeper than 1:1 for heights up to 20 feet. Higher temporary slopes, or any excavations which encounter seepage, should be evaluated by the geotechnical consultant on a case-by-case basis. 4.3.7 Slope Setback As a minimum, all foundations should be setback from any descending slope at least eight feet. The setback should be measured horizontally from the outside bottom edge of the footing to the slope face. The horizontal setback may be reduced by deepening the foundation to achieve the recommended setback distance projected from the footing bottom to the face of the slope. Note that the outer few feet of all slopes are susceptible to gradual down-slope movements due to slope creep. This will affect hardscape such as concrete slabs. We recommend that settlement sensitive structures not be constructed within 5 feet of the slope top without specific review by Group Delta. AWVQ GROUP DELTA Report of Geotechnical Investigation Project No. SD535 Swale Repair July 26, 2017 Versum Materials Page 9 5.0 LIMITATIONS This report was prepared using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable geotechnical consultants practicing in similar localities. No warranty, express or implied, is made as to the conclusions and professional opinions included in this report. The findings of this report are valid as of the present date. However, changes in the condition of a property can occur with the passage of time, whether due to natural processes or the work of man on this or adjacent properties. In addition, changes in applicable or appropriate standards of practice may occur from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside our control. Therefore, this report is subject to review and should not be relied upon after a period of three years. Please feel free call with any questions or comments, or if you need anything else. GROUP DELTA CONSULTANTS Taylor Latimer, PE 82035 Jim Sanders, CEG 2258 Project Engineer Associate Engineering Geologist Distribution: (1) Mr. William Elkins (William.Elkins@versummaterials.com) 91~kOFESS oVk LA I No.C82035 I Lv *EKp._3-31-18 CIVIt. IXF SANDERS I N2258 I cERliPED ENGINEERING * GEOI.OG%SI OF AF~ GROUP DELTA FIGURES S :; -- f' 1 C S A NO SCALE REFERENCE: Google Faith (2016). SateIie imagery dated 11/17/16. C 4 I a Approximate limits of proposed . development. H-4 Sample identification number. -4- Approximate location of sample. A NO SCALE t3RDUP IDELTA DELTA CONSLTL-TANTS, INC. -R5 AND =a 1150535 ;::0 17-0087 EXPLORATION PLAN REFERENCE: Google Earth (2016), Satelite imagery dated 11/8/16. 40 • . .*'. sinpe drainane and swale (Inokinci east from H-2), p Photo 3: Erosion of slope near existing CMU wall and concrete lined slope (looking east) "S S Photo 2: Existing pond immediately vest at site Io K dieast I: ni 11a - - ; .;:.. : ' - .' ' - -' fl - I Photo 4: Standing water and saturated soils near existing drainage (looking west from H-4). Existing pavement Existing slope Existing erosion within slope --------------- Exi tin erosion within slope Ilk Bench excavation to - - - competent subgrade material NO SCALE ENGINEERS AND GEOLOGIStS S0535 CRETE 5 GEOTEXTILE TOP OF SLOPE DETAILS TOE OF SLOPE DETAILS REFERENCE: International Erosion Control Systems Inc. (2010), Key in Detail and Toe in Detail, dated December 9. 1'/2:1 (HORIZONITAL:VERTICAL) MAXIMUM SLOPE INCLINATION 4" THICK CONCRETE SHOTCRETE WITH / 6" by 6", W2.9 by W2.9 WELDED WIRE FABRIC 1- CONCRETE /' GALVINZED METAL SCREEN S WALE 4" DIAMETER WEEP HOLES @10' f-% 04 WITH 1" MAX GRAVEL PLACED 18" ON EACH SIDE OF HOLE & 4" COVER ABOVE AND BELOW HOLE Uj REFERENCE: Ue0techncs Incorporated (2010). Slope Protection, Schumacher Facilities, Document No. 10-0359, Figure 1. APPENDIX A REFERENCES American Society for Testing and Materials (2006). Annual Book of ASTM Standards, Section 4, Construction, Volume 04.08 Soil and Rock (I); Volume 04.09 Soil and Rock (II); Geosynthetics, ASTM, West Conshohocken, PA, Compact Disk. Geotechnics Incorporated (2010). Slope Protection, Schumacher Facilities, 1969 Palomar Oaks Way, Carlsbad, California, Project No. 0272-005-00, Document No. 10-0359, June 10. Group Delta Consultants (2017). Proposalfor Geotechnical Recommendations, Versum Materials - Swale Repair, Carlsbad, California, Proposal No. S017-008, February 7. International Conference of Building Officials (2016). 2016 California Building Code. International Erosion Control Systems Inc., Cable Concrete Specifications, undated. United States Geological Survey (2005). Geologic Map of the San Diego 30' x 60' Quadrangle, California, Kennedy and Tan. GROUP DELTA APPENDIX B LABORATORY TESTING Laboratory testing was conducted in a manner consistent with the level of care and skill ordinarily exercised by members of the profession currently practicing under similar conditions and in the same locality. No warranty, express or implied, is made as to the correctness or serviceability of the test results, or the conclusions derived from these tests. Where a specific laboratory test method has been referenced, such as ASTM or Caltrans, the reference only applies to the specified laboratory test method, which has been used only as a guidance document for the general performance of the test and not as a "Test Standard". A brief description of the various tests performed for this project follows. Classification: Soils were visually classified according to the Unified Soil Classification System as established by the American Society of Civil Engineers per ASTM D2487. The soil classifications are shown on the boring logs in Appendix A. Particle Size Analysis: Particle size analyses were performed in accordance with ASTM D422, and were used to supplement visual classifications. The results are shown in Figures 8-1.1 to B-1.2. Expansion Index: The expansion potentials of selected samples of finish grade soils within the building pad areas were estimated in general accordance with the laboratory procedures outlined in ASTM test method D4829. The test results are summarized in Figure B-2. R-Value: R-Value tests were performed on selected samples of the on-site soils in general accordance with CTM 301. The test results are shown in Figures B-2. pH and Resistivity: To assess the potential for reactivity with buried metals, selected soil samples were tested for pH and minimum resistivity using Caltrans test method 643. The corrosivity test results are summarized in Figure B-3. Sulfate Content: To assess the potential for reactivity with concrete, selected soil samples were tested for water soluble sulfate. The sulfate was extracted from the soil under vacuum using a 10:1 (water to dry soil) dilution ratio. The extracted solution was tested for water soluble sulfate in general accordance with ASTM D516. The test results are also presented in Figure B-3, along with common criteria for evaluating soluble sulfate content. Chloride Content: Soil samples were also tested for water soluble chloride. The chloride was extracted from the soil under vacuum using a 10:1 (water to dry soil) dilution ratio. The extracted solution was then tested for water soluble chloride using a calibrated ion specific electronic probe. The test results are also shown in Figure B-3. £ I3DUP DELTA U.S. Standard Sieve Sizes 100 3" 1W J4' #4 #8 #IA #0 #SU #100 #900 90 92 80 70 FV 60 I.- a, C ii.. 50 40 a) a) 0 30 20 10 0 100 10 1 0.1 0.01 0.001 Grain Size in Millimeters -- --l% Gravel 35% Fines--+ COARSE FINE COARSE MEDIUM FINE SILT AND CLAY GRAVEL SAND SAMPLE UNIFIED SOIL CLASSIFICATION: SC ATERBERG LIMITS BORING NUMBER: H-i LIQUID LIMIT: -- SAMPLE DEPTH: DESCRIPTION: CLAYEY SAND PLASTIC LIMIT: -- PLASTICITY INDEX: -- Project No. SD535 GROUP DELTA SOIL CLASSIFICATION Document No. 17-0087 FIGURE B-1.1 U.S. Standard Sieve Sizes 100 3'1 I4 #50 #100 #200 90 Ilk 88 80 .1m 70 - OD --------- ____ -------- ____ - ____ 60 150 40 30 20 10 A .. - - - - —0% Gravel 65% Sand - 35% Fines— - - - -1i, 0 -- - I - - liii I 100 10 1 0.1 0.01 0.001 Grain Size in Millimeters I COARSE I FINE I COARSE MEDIUM j FINE I SILT AND I I CLAY I I GRAVEL SAND SAMPLE UNIFIED SOIL CLASSIFICATION: SC ATERBERG LIMITS BORING NUMBER: H-2 LIQUID LIMIT: -- SAMPLE DEPTH: DESCRIPTION: CLAYEY SAND PLASTIC LIMIT: - PLASTICITY INDEX: -- GROUP DELTA SOIL CLASSIFICATION Project No. SD535 Document No. 17-0087 041:,Z~w FIGURE B-1.2 R-VALUE TEST RESULTS (CTM 301) SAMPLE NO. DESCRIPTION R-VALUE H-4@ 0'- 1' Fill: Green/Blue Gray Sandy Lean Clay to Clayey Sand (CL/SC). 24 EXPANSION TEST RESULTS (ASTM D4829) EXPANSION SAMPLE NO. DESCRIPTION INDEX H-2 @ 0'- 1' Fill: Light Brown Clayey Sand (SC). 46 H-3 @ 0'- 1' Fill: Light Brown Silty Sand (SM). 33 EXPANSION INDEX POTENTIAL EXPANSION 0 to 20 Very low 21to50 Low 51 to 90 Medium 91 to 130 High Above 130 Very High Project No. 5D535 OUP 0ELT1 LABORATORY TEST RESULTS Document No. 17-0087 FIGURE B-2 CORROSIVITY TEST RESULTS (ASTM D516, CTM 643) RESISTIVITY SULFATE CHLORIDE SAMPLE NO. pH [OHM-CM] CONTENT [%] CONTENT [%] H-3 7.18 607 <0.01 0.01 H-4 7.14 111 0.06 0.29 SULFATE CONTENT [%] SULFATE EXPOSURE CEMENT TYPE 0.00 to 0.10 Negligible - 0.10 to 0.20 Moderate II, IP(MS), IS(MS) 0.20 to 2.00 Severe V Above 2.00 Very Severe V plus pozzolan SOIL RESISTIVITY [OHM-CM] GENERAL DEGREE OF CORROSIVITY TO FERROUS METALS 0 to 1,000 Very Corrosive 1,000 to 2,000 Corrosive 2,000 to 5,000 Moderately Corrosive 5,000 to 10,000 Mildly Corrosive Above 10,000 Slightly Corrosive CHLORIDE (CI) CONTENT GENERAL DEGREE OF [%] CORROSIVITY TO METALS 0.00 to 0.03 Negligible 0.03 to 0.15 Corrosive Above 0.15 Severely Corrosive Project No. SD535 GROUP DELTA LABORATORY TEST RESULTS Document No. 17-0087 FIGURE B-3