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HomeMy WebLinkAboutGB150116_GB150061.GB150116GeoRptFinal20180121 GEOTECHNICAL, INC. 23241 Arroyo Vista  Rancho Santa Margarita, CA 92688  phone: 949.888.6513  fax: 949.888.1380  info@gmugeo.com  www.gmugeo.com Report of Geotechnical Observation and Testing of Precise Grading and Site Improvements, Lots 1 through 20 of Tract No. 15613 and Lots 1 through 7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast, Orange County, California Prepared For THE NEW HOME COMPANY January 25, 2018 GMU Project No. 15-093-10 Permit Nos.: Model – GB150061 Production – GB150116 Project Address: Spinnaker/South Sur/Tide Watch GEOTECHNICAL, INC. 23241 Arroyo Vista  Rancho Santa Margarita, CA 92688  phone: 949.888.6513  fax: 949.888.1380  info@gmugeo.com  www.gmugeo.com TRANSMITTAL Ms. Holly Slevcove THE NEW HOME COMPANY DATE: January 25, 2018 85 Enterprise, Suite 450 Aliso Viejo, CA 92656 GMU PROJECT: 15-093-10 SUBJECT: Report of Geotechnical Observation and Testing of Precise Grading and Site Improvements, Lots 1 through 20 of Tract No. 15613 and Lots 1 through 7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast, Orange County, California DISTRIBUTION: Addressee: One wet signature copy and electronic copy The New Home Company Attn: Mr. Eric Porterfield (electronic copy) Hunsaker & Associates Irvine, Inc. Attn: Mr. David Franke (electronic copy) County of Orange Attn: District Inspector (One wet signature copy) Ms. Holly Slevcove, THE NEW HOME COMPANY Geotechnical Observation & Testing: Lots 1-20 of Tract No. 15613 and Lots 1-7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast January 25, 2018 i GMU Project 15-093-10 TABLE OF CONTENTS Description Page INTRODUCTION .............................................................................................................................1 PURPOSE .............................................................................................................................1 LOCATION ...........................................................................................................................1 SCOPE ...................................................................................................................................1 PRECISE GRADE OBSERVATIONS AND TESTING ..................................................................2 GENERAL ............................................................................................................................2 RESIDENTIAL AND CASITA FOUNDATION EXCAVATIONS AND SLAB SUBGRADE CONSTRUCTION ...........................................................................3 WALL, PILASTER, SHADE STRUCTURE, WATER FEATURE, FIRE PIT, AND BARBEQUE FOOTING EXCAVATIONS ............................................................3 UTILITY TRENCH BACKFILL ..........................................................................................4 RETAINING WALL BACKFILL ........................................................................................5 SWIMMING POOL AND SPA EXCAVATIONS ...............................................................5 SWIMMING POOL AND SPA DECK SUBGRADE PREPARATION .............................6 HARDSCAPE AND DRIVEWAY SUBGRADES ..............................................................6 TESTING PROCEDURES ................................................................................................................6 CONCLUSIONS................................................................................................................................7 GEOTECHNICAL SUITABILITY ......................................................................................7 FUTURE SITE SOIL MOVEMENTS AND EFFECTS ON SITE IMPROVEMENTS ......7 FUTURE IMPROVEMENTS ...............................................................................................8 BUILDER DISCLOSURE TO HOMEOWNERS ................................................................8 RECOMMENDATIONS ...................................................................................................................9 LIMITATIONS ..................................................................................................................................9 CLOSURE ...................................................................................................................................10 REFERENCES ..................................................................................................................................11 PLATES Plate 1 -- Location Map Plates 2.1 through 2.13 -- Geotechnical Map Plate 3 -- Summary of Compaction Curve Data Plates 4.1 through 4.4 -- Results of Field Density Tests APPENDIX -- “Co-existing with Expansive Soil – An Informational Guide for Homeowners” by California Geotechnical Engineering Association (CalGeo) January 25, 2018 1 GMU Project 15-093-10 INTRODUCTION PURPOSE This report summarizes the results of our geotechnical observation and testing relevant to the precise grading and on-site improvements for Lots 1 through 20 of Tract No. 15613, and Lots 1 through 7 of Tract No. 16604, Coral Crest development, within the Crystal Cove community in Newport Coast, Orange County, California. LOCATION The Coral Crest development is located adjacent to Spinnaker, South Sur, and Tide Watch within the Crystal Cove community. The location of the project with respect to the surrounding area is shown on Plate 1 of this report. SCOPE Our scope consisted of the following: • Performed periodic observation and testing during precise grading, foundation and footing excavations, slab subgrade preparation, utility trench and wall backfill, hardscape and driveway subgrade preparation and sub-base placement, and construction of associated on-site improvements. • Performed laboratory testing to determine the engineering properties of the typical on-site and imported soil and rock materials. • Prepared this report summarizing the results of our observation and testing. Our scope did not include any surveying, grading plan design, safety engineering, or testing related to determining the presence of toxic or hazardous materials. Ms. Holly Slevcove, THE NEW HOME COMPANY Geotechnical Observation & Testing: Lots 1-20 of Tract No. 15613 and Lots 1-7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast January 25, 2018 2 GMU Project 15-093-10 PRECISE GRADE OBSERVATIONS AND TESTING GENERAL The precise grading and associated improvements, as shown on the reference (1) and (2) plans, consisted of making minor cuts and fills to create the subgrades for the residential structures, casitas, and associated driveways, hardscape, and landscape areas for Lots 1 through 20 of Tract No. 15613 and Lots 1 through 7 of Tract No. 16604. Additional landscape improvements for the homeowners were constructed by the builder during the precise grading for the project at Lots 2, 3, 6, and 19 of Tract No. 15613 and Lots 3 and 6 of Tract No. 16604. These landscape improvements have been incorporated into the reference (2) grading plans utilized as the base maps for our Geotechnical Maps included in this report. General precise grade observations and testing are summarized below: • Prior to the start of the grading and construction of site improvements, all significant amounts of organic materials, construction debris, and temporary drainage improvements present at the site were observed to be removed and disposed of off-site. • In addition, the subject lots had the upper up to about 24 inches of dry and desiccated soil materials removed as necessary to expose competent, previously placed engineered fill materials prior to the start of the precise grading and construction of on-site improvements. • The rear yard basins located within the subject lots were cleared of any organic materials, temporary drainage improvements, and unsuitable soil materials to expose previously placed engineered fill materials. • Prior to placing any fill materials, areas to receive fill and shallow cut areas were scarified, moisture conditioned as necessary to over optimum moisture content, and compacted in accordance with the project geotechnical recommendations. • The temporary Model Site improvements (i.e., parking lot, walkways, landscape, and associated temporary improvements) at Lots 6 through 9 were removed as necessary during the model build-out and observed to be disposed of off-site. Following the removal of the subject Model Site improvements, the upper 8 to 24 inches of the soil materials within the impacted areas were removed as necessary to expose competent engineered fill materials. The removal bottoms were scarified, moisture conditioned as necessary to over optimum moisture content, and compacted in accordance with the project geotechnical recommendations. • The native soils used for backfill and fill materials were placed in thin lifts, moisture conditioned to over optimum moisture content, and compacted in accordance with the project geotechnical recommendations. Ms. Holly Slevcove, THE NEW HOME COMPANY Geotechnical Observation & Testing: Lots 1-20 of Tract No. 15613 and Lots 1-7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast January 25, 2018 3 GMU Project 15-093-10 • The subgrade soil materials underlying the hardscape and driveways were scarified, moisture conditioned as necessary to over optimum moisture content, and compacted in accordance with the project geotechnical recommendations. • Periodic hand-probing of foundations, footings, subgrades, and native soil backfill and fill materials was performed during the course of the project. RESIDENTIAL AND CASITA FOUNDATION EXCAVATIONS AND SLAB SUBGRADE CONSTRUCTION Our observations are summarized below: • The foundations and slab subgrades were excavated into engineered fill materials suitable for the support of the planned improvements. • The foundation excavations were moisture conditioned as necessary to over optimum moisture content. • The backfill for the interior utility trenches is described in a subsequent section of this report. • The slab subgrade areas were observed to be moisture conditioned to over optimum moisture content in accordance with the project geotechnical recommendations. • The foundations and slab subgrade areas were observed to be constructed in general accordance with the recommendations included in our references. WALL, PILASTER, SHADE STRUCTURE, WATER FEATURE, FIRE PIT, AND BARBEQUE FOOTING EXCAVATIONS Our observations are summarized below: • The subject footings were excavated into soil materials suitable for the support of the planned improvements in areas observed by GMU Geotechnical, Inc. (GMU). • The footings were observed to be constructed in general accordance with the recommendations included in our references in areas observed by GMU. • The footing excavations were moisture conditioned as necessary to over optimum moisture content in areas observed by GMU. • The top-of-slope side yard wall returns are founded on caisson and grade beam foundation systems which were observed to be constructed in general accordance with the recommendations included in our references. Ms. Holly Slevcove, THE NEW HOME COMPANY Geotechnical Observation & Testing: Lots 1-20 of Tract No. 15613 and Lots 1-7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast January 25, 2018 4 GMU Project 15-093-10 UTILITY TRENCH BACKFILL Backfill observations and testing are summarized below: • The subgrades for the utilities were excavated into soil materials suitable for the support of the utility improvements in areas observed by GMU. • The pipe/conduit zone materials generally consisted of imported sand meeting our recommendations and were observed to be consolidated via jetting and/or flooding and compacting in areas observed by GMU. • The interior utility trenches were backfilled entirely with imported sand materials which were consolidated via jetting, flooding, and mechanically compacting. • The backfill for the irrigation line trenches consisted entirely of native soil materials placed utilizing the methods described previously in this report. • The native soil backfill materials were placed utilizing the methods previously described in this report. In addition, the native soil backfill materials were periodically hand- probed during placement and found to be suitable for their intended use. • It should be noted that observations only were provided for the deeper trench backfill zones. When the backfill materials reached a depth where it was deemed safe to enter, field density testing was initiated. The following table summarizes the approximate maximum depths of the utility trenches. Note that the actual backfill depths are generally shallower than those listed below following the placement of the piping/conduit and pipe/conduit zone backfill materials. Utility Trench Maximum Trench Depth Sewer 14 feet Waterline 2 feet Common Utility (i.e., cable t.v., electrical, telephone, gas) 10 feet (~5 feet) Storm and Area Drain 8 feet Interior Utility 4 feet Irrigation 3 feet Electrical 18 inches Pool/Water Feature Utility 2 feet Ms. Holly Slevcove, THE NEW HOME COMPANY Geotechnical Observation & Testing: Lots 1-20 of Tract No. 15613 and Lots 1-7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast January 25, 2018 5 GMU Project 15-093-10 RETAINING WALL BACKFILL Our observations and testing are summarized below: • A waterproofing agent was observed to be applied to the back side of the walls (design and inspection not within GMU’s purview). • The backdrain systems for the walls consisted of 4-inch-diameter SDR 35 or Schedule 40 perforated PVC pipe surrounded by a minimum of 1 cubic foot of ¾-inch crushed rock materials per lineal foot of pipe wrapped in Mirafi 140N filter fabric or equivalent. • The wall backdrain systems are outletted into the site area and storm drain systems. • The wall backfill above the backdrain systems consisted of imported sand materials or pea gravel materials. The backfill materials were placed in thin lifts, moisture conditioned to over optimum moisture content conditions (sand), and compacted in accordance with the project geotechnical recommendations. The imported sand and pea gravel materials were placed to within about 2 to 2½ feet of finish grade. The remaining backfill consisted of native soil materials placed utilizing the methods described previously in this report. SWIMMING POOL AND SPA EXCAVATIONS Our observations and testing are summarized below: • Swimming pools and spas were constructed at Lots 2, 6, 7, and 8 of Tract No. 15613, and Lots 3 and 6 of Tract No. 16604. A spa, but no pool, was constructed at Lot 9, Tract 15613. • Caisson and grade beam foundation systems were utilized for all of the pools and spas, with the exception of Lot 6 of Tract No. 15613, which utilized a conventional foundation system. • The pool/spa foundation systems and pool/spa shells were excavated into soil materials suitable for the support of the planned pool and spa improvements. • It should be noted that the pool and spa caissons within Lot 2 of Tract No. 15613 were excavated in locations that were not according to the plan. These caisson excavations were observed to be backfilled with a 2-sack sand-cement slurry mixture to grade. The correct locations of the pool and spa caissons were then excavated. • Subdrain systems were installed within the pool bottom subgrades. The subdrain systems consist of 4-inch-diameter perforated SDR 35 or Schedule 40 plastic pipe wrapped in a filter sock and surrounded with at least 1 cubic foot of ¾-inch crushed rock per lineal foot of pipe. The subdrain systems are outletted into the adjacent on-site storm/area drain systems. Ms. Holly Slevcove, THE NEW HOME COMPANY Geotechnical Observation & Testing: Lots 1-20 of Tract No. 15613 and Lots 1-7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast January 25, 2018 6 GMU Project 15-093-10 SWIMMING POOL AND SPA DECK SUBGRADE PREPARATION Our observations and testing are summarized below: • The swimming pool and spa deck subgrade areas were excavated into engineered fill materials suitable for the support of the planned decking improvements. • The subject deck areas were moisture conditioned as necessary to over optimum moisture content in accordance with the project geotechnical recommendations. HARDSCAPE AND DRIVEWAY SUBGRADES Our observations are summarized below: • The subject subgrades were excavated into engineered fill materials suitable for the support of the planned improvements in areas observed by GMU. • The subgrade areas were moisture conditioned to over optimum moisture content conditions in accordance with the project geotechnical recommendations in areas observed by GMU. • Prior to pouring the concrete, a minimum of 2 inches of aggregate base or imported sand materials were placed over the moisture conditioned subgrades and mechanically compacted. It should be noted that, as directed by the County Inspector, sub-base materials were not placed in the areas within the jurisdiction of the County of Orange. TESTING PROCEDURES The following test procedures were utilized: Test Test Method Test Results Compaction tests ASTM D 1557 Listed on Plate 3 Field density tests* ASTM D 6938 Listed on Plates 4.1 through 4.4 Sand equivalent tests ASTM D 2419 30 to 47 * The locations of our field density tests are shown on Plates 2.1 through 2.13 of this report. Ms. Holly Slevcove, THE NEW HOME COMPANY Geotechnical Observation & Testing: Lots 1-20 of Tract No. 15613 and Lots 1-7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast January 25, 2018 7 GMU Project 15-093-10 CONCLUSIONS GEOTECHNICAL SUITABILITY • It is our opinion, based on the results of our observation and testing, that the subject precise grading and construction of on-site improvements for Lots 1 through 20 of Tract No. 15613 and Lots through 7 of Tract No. 16604 have been completed in general conformance with our references. • The graded slopes are grossly and surficially stable under normal conditions of rainfall, landscape irrigation, erosion control, and proper maintenance. • The site is underlain with expansive soils which will induce soil movements with changes in moisture content. Consequently, some movement-related distress may occur and should be expected (i.e., minor cracking and/or separations of appurtenant structures). See the following section for additional detail and discussion. FUTURE SITE SOIL MOVEMENTS AND EFFECTS ON SITE IMPROVEMENTS Although recommendations have been incorporated into the design of the developer-installed on-site improvements to minimize the effects of soils movements, the subject lots will be affected by future lateral soil movements related to soil creep and lateral fill extension (i.e., post- construction slope movements) as well as vertical movements related to expansion/contraction and settlement. The developer-installed improvements have only been designed to minimize the effects of the movements. All of these movements, should they occur, cannot be stopped nor prevented and should be considered normal. Typical soil movements are as follows: • The lateral movements could cumulatively be on the order of several inches extending across the lot from the backyard to the front yard sidewalk as well as some tilting of the ground surface. Typically, movements are greatest in deep fill areas and in areas located near the tops of descending slopes, while movements are less in shallow fill areas and areas of level ground. • These movements typically result in: i) flatwork separations, ii) separations in exterior side-yard wall joints, iii) separation between top-of-slope walls and adjacent structures, iv) separation between buildings and patios located near the tops of descending slopes, v) separation between buildings and adjacent walkways, vi) separations between the driveway slab and the sidewalk, and vii) rotation of building floor slabs as reflected in post-construction manometers. Ms. Holly Slevcove, THE NEW HOME COMPANY Geotechnical Observation & Testing: Lots 1-20 of Tract No. 15613 and Lots 1-7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast January 25, 2018 8 GMU Project 15-093-10 • Typical flatwork separations are on the order of 1 to 2 inches, with cumulative movements (i.e., resulting from both lateral movements and vertical expansion/contraction) ranging from 2 to 6 inches across the lots. • Foundation slab movements typically can result in a post-construction manometer reading indicating 1 to 3 inches of elevation change across the structure. FUTURE IMPROVEMENTS A geotechnical engineer should be utilized to aid in the design of all future improvements. Without proper engineering guidance, the performance of owner-installed improvements will likely result in unacceptable performance. Other important items to note in this regard include the following: • All future site improvements (i.e., especially pools and additions, but also including walls, fences, patio covers, flatwork, etc.) must be designed with consideration to the above discussed movements. Specific recommendations should be provided by a geotechnical engineer hired by the homeowner. • Future pools/spas placed in top of slope backyard areas will need “above-normal design” elements (i.e., deeper structural keyways, caissons, decking structurally tied to the pool shell, etc.) and may undergo some rotation. Specific recommendations and design will need to be provided by a geotechnical and pool design engineer hired by the homeowner. • The foundations for the residential and casita (where applicable) structures at each lot are constructed with post-tension foundation systems. Any addition by the homeowner that is structurally connected to the residential structure should be designed by a structural engineer hired by the homeowner experienced with post-tension foundations, and must consider the potential for differential movements between the addition and the residential structure. BUILDER DISCLOSURE TO HOMEOWNERS The above described typical post-construction movements as well as requirements for future homeowner improvements should be passed on to all homeowners. It is highly recommended that the builder obtain specific acknowledgement from the homeowners in regards to this issue. Additionally, a copy of “Coexisting with Expansive Soil – An Informational Guide for Homeowners” developed by The California Geotechnical Engineering Association (CalGeo), should be passed on to future homeowners. A copy is included in this report as an Appendix. Ms. Holly Slevcove, THE NEW HOME COMPANY Geotechnical Observation & Testing: Lots 1-20 of Tract No. 15613 and Lots 1-7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast January 25, 2018 9 GMU Project 15-093-10 RECOMMENDATIONS • Care should be taken to confirm that surface drainage within the project conforms to the project grading plan. • Ponding of surface runoff or over-irrigation could result in moisture problems within structures, softening and weakening of pavement and hardscape subgrades, and/or saturation and potential failures of slope areas. • The on-site expansive soils are subject to volume change (both expansion and contraction) as a result of changes in moisture. Future planting, irrigation, landscaping, and maintenance should therefore strive to maintain a uniform soil moisture content that is similar to the moisture content at which the fills were placed. Furthermore, the fills should not be allowed to become excessively dry or saturated. • All future improvements shall be designed in minimum accordance with the “Future Site Soil Movements and Effects on Site Improvements” section of this report (see Page 7). LIMITATIONS In reviewing the data, conclusions, and recommendations presented in this report, it should be recognized that our work does not constitute a guarantee that the contractors have performed their work in accordance with the project plans, reports, and specifications. We believe that we have exercised a degree of care comparable to that presently maintained by other professionals in the fields of geotechnical engineering and engineering geology and have performed sufficient observation and testing to provide a rational basis for our opinion that the grading and improvements completed to date were performed in general accordance with our geotechnical recommendations. This report has not been prepared for the use by other parties or projects other than those named or described herein. This report may not contain sufficient information for other parties or other purposes. Ms. Holly Slevcove, THE NEW HOME COMPANY Geotechnical Observation & Testing: Lots 1-20 of Tract No. 15613 and Lots 1-7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast January 25, 2018 10 GMU Project 15-093-10 CLOSURE We are pleased to present the results of our geotechnical observation and testing of precise grading and site improvements for the project. The Plates and Appendix that complete this report are listed in the Table of Contents. If you have any questions concerning our findings or recommendations, please do not hesitate to contact us. Respectfully submitted, GMU GEOTECHNICAL, INC. Alan B. Mutchnick, PG, CEG 1789 Associate Engineering Geologist David Hansen, M.Sc., PE, GE 3056 Senior Geotechnical Engineer rah/15-093-10R (01-25-18) Ms. Holly Slevcove, THE NEW HOME COMPANY Geotechnical Observation & Testing: Lots 1-20 of Tract No. 15613 and Lots 1-7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast January 25, 2018 11 GMU Project 15-093-10 REFERENCES (1) Model Precise Grading Plan & Buildout, Revision No. 3, Tract No. 15613, Lots 6-9, County of Orange, dated June 14, 2017, prepared by Hunsaker & Associates Irvine, Inc. (Their W.O. 2749-13). (2) Production Precise Grading Plan, Revision No. 8, Tract No. 16604 & 15613, Coral Crest, LLA 2014-018, LLA 2014-019, LLA 2014-020, County of Orange, dated June 20, 2017, prepared by Hunsaker & Associates Irvine, Inc. (Their W.O. 2749-13). (3) Our “Clarification of Site Wall Foundation Recommendations, Coral Crest Models, Lots 6 through 9, Tract 15613, Crystal Cove, Newport Coast, County of Orange, California,” dated July 17, 2017 (GMU Project 15-093-00). (4) Our “Geotechnical Review of Delta 8 Revision of Precise Grading Plans, Coral Crest Production Units, Lots 1 through 7 of Tract No. 16604 and Lots 1 through 5 and 10 through 20 of Tract 15613, Crystal Cove, Newport Coast, County of Orange, California,” dated June 30, 2017 (GMU Project 15-093-00). (5) Our “Geotechnical Review of Delta 3 Revision of Precise Grading Plans, Coral Crest Model Site, Lots 6 through 9 of Tract 15613, Crystal Cove, Newport Coast, County of Orange, California,” dated June 16, 2017 (GMU Project 15-093-00). (6) Our “Geotechnical Review of Revised Site Retaining Wall and Property Line Wall Plans, Details and Calculations, Coral Crest, Lots 1-7 of Tract 16604 and Lots 1-5 and 10-20 of Tract 15613, Crystal Cove Development, Orange County, California,” dated March 17, 2016 (GMU Project 15-093-00). (7) Our “Geotechnical Review of Post-Tension Foundation Plans and Details, Coral Crest Production Units, Tract 15613, Crystal Cove Development, Orange County, California,” dated March 3, 2016 (GMU Project 15-093-00). (8) Our “Geotechnical Review of Drainage Variance Request, Coral Crest Production Sites, Lots 1 through 7 of Tract 16604 and Lots 1 through 5 and 10 through 20 of Tract 15613, Crystal Cove, Newport Coast, County of Orange, California,” dated January 26, 2016 (GMU Project 15-093-00). (9) Our “Geotechnical Review of Production Precise Grading Plan, Coral Crest Site, Lots 1 through 7 of Tract 16604 and Lots 1 through 5 and 10 through 20 of Tract No. 15613, Crystal Cove, Newport Coast, County of Orange, California,” dated January 20, 2016 (GMU Project 15-093-00). Ms. Holly Slevcove, THE NEW HOME COMPANY Geotechnical Observation & Testing: Lots 1-20 of Tract No. 15613 and Lots 1-7 of Tract No. 16604, Coral Crest, Crystal Cove, Newport Coast January 25, 2018 12 GMU Project 15-093-10 (10) Our “Geotechnical Review of Pool and Spa Plans and Details, Coral Crest Models, Lots 7-9, Tract 15613, Crystal Cove Development, Orange County, California,” dated December 18, 2015 (GMU Project 15-093-00). (11) Our “Geotechnical Review of Site Retaining Wall Foundation Plans and Details, Coral Crest Models, Tract 15613, Crystal Cove Development, Orange County, California,” dated October 15, 2015 (GMU Project 15-093-00). (12) Our “Geotechnical Review of Drainage Variance Request, Coral Crest Model Site, Lots 6 through 10, Tract 15613, Crystal Cove, Newport Coast, County of Orange, California,” dated September 3, 2015 (GMU Project 15-093-00). (13) Our “Geotechnical Review of Post-Tension Foundation Plans and Details, Coral Crest Models, Tract 15613, Crystal Cove Development, Orange County, California,” dated July 31, 2015 (GMU Project 15-093-00). (14) Our “Geotechnical Review of Model Precise Grading Plan, Coral Crest Site, Lots 6 through 9, Tract No. 15613, Crystal Cove, Newport Coast, County of Orange, California,” dated July 20, 2015 (GMU Project 15-093-00). APPENDIX “Co-existing With Expansive Soil – An Informational Guide for Homeowners,” by California Geotechnical Engineering Association (CalGeo) Coexisting with expansive soil: An Informational Guide for Homeowners 1 overview Homes in California are built on a variety of soil types with differing characteristics that can affect homes and surrounding improvements in different ways.  So called expansive soils are particularly noteworthy because they can cause significant property damage, if not properly addressed. Clayey soils can swell and exert thousands of pounds of force as they absorb water from irrigation, rain or other sources---enough to lift buildings and crack concrete. Other potential effects around homes may include lifting and cracking of patio slabs, tilting and cracking of walls, and lateral displacement of improvements towards slopes. You can determine if your property has expansive soils from your home buyer’s disclosures, the local building department, or geotechnical professionals (soil engineers and geologists). If your property has expansive soil, there are important things you should know in order to properly maintain your home and associated improvements – and to properly construct any additional improvements you may want. To begin, you should: •Become familiar with how expansive soils behave; •Maintain good drainage on your property; •Practice consistent and measured landscape irrigation; •Inspect your yard and improvements frequently for maintenance items; •Repair broken irrigation and plumbing leaks promptly; •Keep concrete cracks and joints sealed to reduce water infiltration; •Consult with qualified geotechnical professionals when making changes or improvements to your home; •For new construction, incorporate design and construction measures that will mitigate potential expansive soil effects to a degree that is acceptable to you; •Hire licensed contractors that have experience with expansive soils; •Note that additional construction costs associated with addressing expansive soil may be small relative to the costs required to repair damaged improvements at a future date. 2 If you are reading this booklet, your home may be constructed on expansive soil (sometimes referred to as swelling or heaving soil). Your home buyer’s disclosure document will typically address this issue. You can also check with the local building department and a qualified geotechnical professional. They will usually know if expansive soil is found in your area. Because it is common, building codes have specific requirements for new homes and other improvements constructed on expansive soil. You should read your home buyer’s disclosure documents and this booklet to make sure you know the important considerations regarding the design, installation and maintenance of improvements on your property. This information can help you avoid costly and frustrating experiences with expansive soil. This is a publication prepared by some members of the California Geotechnical Engineering Association, so the information about expansive soil and the measures taken to reduce its impacts may be particular to California but in many cases the general principles will apply regardless of geographic region. This guide will help you understand some of the basics about expansive soil. However, it is not intended to be a substitute for consultation with a qualified geotechnical professional to evaluate your specific property. The basic expansive soil issues you should be familiar with include: •Its nature and behavior •How it can affect your home and other improvements on your property •Principles for designing and constructing landscaping, patios, pools, etc. •Proper maintenance practices, and •Reasonable performance expectations for home improvements. If you are embarking on a home improvement project, make sure your project team (architects, engineers, and contractors) is aware of issues associated with expansive soil. 3 what is expansive soil? An expansive soil is a clay-rich soil that swells or shrinks when its moisture content increases and decreases. Certain clay minerals in soil have an affinity for water and can absorb large amounts of water. When they do, they can increase in volume (swell). The opposite is also true - as they dry and lose water, they decrease in volume (shrink). Clayey soil can crack as its dries. Vertical and/or horizontal ground movement can occur when significant changes in moisture levels occur in expansive soils. Soils have varying amounts of expansion potential depending on the type and amount of clay that they contain. Geotechnical professionals usually classify soils as having very low, low, medium, high or very high expansion or swell potential according to guidelines in building codes. There are specific laboratory tests to evaluate a soil’s expansion potential. expansive soil basiCs: •Some amount of ground movement is unavoidable when expansive soils are present. •Most movement typically occurs within the first few years of any changes in construction or improvements to the site (such as changes in landscaping) until soil moisture nears or approaches equilibrium. •Some longer term cyclical soil movement may continue to occur in response to seasonal changes in soil moisture. There are several general types of ground movement associated with expansive soils that can affect a property. These include heave, settlement, and lateral movements near top of slope areas. It is often difficult to differentiate between ground movement caused by expansive soil and other soil phenomena. Heave. The forces exerted by swelling expansive soil can be large. Builders attempt to design and construct house foundations such that they are strong enough to accommodate expansive soil movement with little adverse effects. Minor cracking and cosmetic distress can still occur with properly designed structures. Swelling soil can also cause other improvements around a home - such as driveways, patio slabs, walls, and pools to lift, tilt, or move laterally. If excessive, these types of movements can be aesthetically objectionable. If pools and spas are not designed to accommodate expansive soil, they may crack or plumbing may be damaged and leak. This can cause additional soil wetting and possibly even more heaving. 4 Settlement. As expansive soil dries out, it will shrink. If it shrinks enough, the ground surface may drop perceptably. Supported improvements may also drop or tilt and develop cracks or separations. This type of ground movement may also displace improvements laterally, resulting in cracks or gaps at joints. Top of Slope Movements. Properties located at the tops of slopes that have expansive soil will undergo lateral and vertical soil movements when the soil swells or shrinks. One type of movement is referred to as Lateral Fill Extension (LFE). LFE will occur when soil moisture levels increase following the grading of a slope. As the soil absorbs moisture, it expands. This expansion is accommodated by ground movement in the direction of least resistance. Away from slopes, the primary direction of ground movement will be upwards (heave). However, closer to the slope, the direction of movement will largely be outwards towards the face of the slope. The lower amount of heave along the top of the slope is often mistaken as settlement. The lateral movement near the tops of slopes will often displace improvements in that area; patio slabs may develop gaps where they meet the house; columns for patio structures may develop a “lean” if the tops are attached to the home; gaps may develop around the perimeter of pools; and the construction joints in side yard walls may get wider in response to this type of ground movement. Another type of movement associated with expansive soils and slopes is called slope creep. Slope creep can occur along the face of a slope and within a short distance back from the top of the slope. With slope creep, seasonal or other cyclic wetting and drying of the near surface soils causes those soils to creep slowly down slope under their own weight. Distinguishing between the effects of slope creep and LFE is sometimes difficult. Slope creep can be reduced by maintaining uniform soil moisture levels. As noted previously, there are many mechanisms unrelated to expansive soils that can cause ground movement and related distress. A site specific assessment by a geotechnical professional, structural engineer, or other construction professional may be necessary to identify the cause(s) of any observed distress. 5 what is done to reduCe expansive soil problems during ConstruCtion? Land developers and home builders take a number of measures during site grading and home construction to reduce the impacts of expansive soil. Some of these measures are required by local and national building codes while others are based on local experience and the recommendations of the design team. Here are a few examples of such measures: •During grading and construction, water may be added to soil to reduce its potential for absorbing large amounts of water after a home is completed. This reduces its swelling potential. •Residential lots are typically designed and graded to direct surface runoff water away from the perimeter of the home, away from slope areas, and toward suitable drains or gutters. •Foundation and floor slab systems are designed and constructed to be rigid enough to accommodate expansive soil movements without significant damage. •Homes are set back from the tops of slopes in accordance with building code requirements to reduce the effects of LFE and slope creep on those structures. •Walls and other improvements at the tops of slopes may have deepened foundations, heavier reinforcement, and/or joints and connections to accommodate movement. what Can homeowners do to reduCe problems from expansive soil? Maintenance Proper maintenance of both developer-installed and homeowner-installed improvements is a key to reducing expansive soil related problems. Homes and improvements on expansive soil must be maintained regularly. Some improvements will require periodic repairs to keep up their appearances and performance. important maintenanCe prinCiples related to expansive soil: A. Water your yard in moderation but also consistently. To avoid significant changes in soil moisture, you will likely need to water more in dry times and less in wetter seasons. Don’t turn off your irrigation, if you are going to be away from home for an extended time, especially during dry weather. B. Repair water leaks and breaks in irrigation systems, plumbing, pools and spas promptly. 6 C. Verify that properties adjacent to your lot, especially slopes that are owned by others (e.g., city, association, or neighbor) are properly maintained and irrigated. Notify the owners of those properties if you identify issues that may adversely affect your property. D. Keep water away from places it normally does not belong. For example, if gaps or cracks in patio slabs or pool decks develop, repair or seal them promptly to reduce the potential for water infiltration. E. Maintain proper drainage on your property. Don’t let water flow to, or collect in places where it can cause soils to become overly wet. Don’t modify the ground level or surface drainage pattern at your property without consulting a knowledgeable construction or design professional. Make sure drain inlets are at, or just below, the ground surface level so water can flow into them. F. Inspect your property and improvements for the effects of expansive soil frequently and perform maintenance as needed. Pay particular attention to areas near slopes, perimeter walls (including walls shared with others) and connections where wall types change. For instance, gates, and connections between wrought iron fence and masonry wall will periodically need adjustments. If you are unsure of what to look for or if you notice something particularly concerning, consult a qualified professional for advice. NOTE: Even with proper maintenance, the effects of expansive soil cannot be totally eliminated. You should expect some amount of periodic (and seasonal) adjustment, repair and/or replacement of the affected features. new ConstruCtion If you hire people to assist you with an improvement project, we recommend that you verify they are properly licensed (also bonded if contractors). In California, pool and landscaping contractors are required to be licensed. Professional and contracting licenses can be checked via the internet in California and other states. When installing exterior improvements at a property with expansive soils, precautionary measures should be taken during both the design and construction phases of the project. 1. Design Measures: Depending on the complexity of your project, you may need to consult with a professional who is familiar with expansive soil and methods to reduce the potential problems associated with it. The designers and contractors you enlist should be qualified and experienced with building on expansive soils. Many building departments require a licensed geotechnical engineer to be involved in the design and construction of such things as pools, retaining walls, and house additions. Addressing some of the principles may determine how well your improvements perform. 7 Keep in mind that: A. Some amount of ground movement should be anticipated when designing improvements on expansive soil. You should consult with a geotechnical engineer – and other design professionals, as necessary – to determine the pattern and amount of ground movement that is expected, in order to ensure that the improvements will perform in an acceptable manner under those conditions. B. Ground movements associated with LFE and slope creep will be greater near the top (edge) of the slope. Keep sensitive and costly structures like pools, spas, home additions, and barbecues islands as far away from the top of the slope as possible. As they get closer to the slope, more rigorous measures against expansive soil movement will be required in their design and construction. Most building codes provide minimum set-back guidelines for structure foundations and pools constructed adjacent to slopes. Additional precautions are typically necessary for any improvements that are to be constructed within slope set-back zones. C. Expansive soil forces on improvements like patio slabs, pools, and decks can be very large. Reinforcing, strengthening, and connecting (or purposely disconnecting) such improvements must be carefully considered. D. Some tilting of pools located in slope areas is likely to occur over extended periods of time. Pool shells should be designed to accommodate this movement. The trim and other detailing around the perimeter of the pool should be designed to accommodate the expected movement. E. Trees and similar vegetation with large root systems will draw moisture out of the soil, resulting in soil shrinkage and ground settlement. Foundations and other improvements next to such landscaping can be affected. Consult a landscape architect familiar with expansive soil issues before installing exterior landscaping. F. Large sections of continuous flatwork extending back from top of slope areas should be avoided. Sections of properly reinforced flatwork should be separated by landscaping zones, joints, or other architectural features to accommodate movement in an aesthetically acceptable manner. G. Existing walls and fences may not be designed as retaining walls. Placing additional soil behind retaining walls, or against non-retaining walls, may cause them to move or even fail. Ensure that excess soil generated from your project will be placed in appropriate area or disposed of offsite. 8 2. Construction Measures: A proper design is of little value if it is poorly executed. The following guidelines apply to the construction phase of home improvement projects: A. Be sure to hire contractors that are licensed, qualified, conscientious, and understand expansive soil issues. Make sure you have a written contract which clearly defines the contractor’s scope of work, costs, and other terms of your agreement. Verify that specific and appropriate measures have been taken to mitigate the effects of expansive soils. B. Don’t let expansive soils dry out before or during construction. The soils can be covered with plastic or wetted prior to construction, as necessary, to ensure proper moisture. In some cases, pre- wetting for extended periods of time (days or even weeks) may be necessary. Generally, however, pre-wetting should only be done in consultation with a geotechnical professional. Fill placed during construction should have proper moisture content and compaction. Pre-wetting of soils is particularily important where patio decks abut swimming pools. Without proper ground preparation, a patio deck supported on the ground surface is likely to heave more relative to a pool shell supported at a greater depth. C. Trust but verify. Don’t assume that the local building inspector (if involved) will look at everything. For many projects, you should consider hiring a professional to provide independent verification that the mitigation measures related to expansive soil are being properly carried out by your contractor. Examples of other design measures and practices that address expansive soil are provided in the appendix at the end of this booklet. Unfortunately, building on expansive soil may increase construction costs. However, these costs are normally much less than the maintenance and repair costs for projects that are inadequately designed or constructed. How far you go and what measures you decide to take depend not only on your budget, but also on your architectural choices, your tolerance for the effects of expansive soil such as tilting, gaps and cracking, and your expectations for future maintenance and routine repairs. living with expansive soil Too many homeowners are unaware of the nature of expansive soil and potential issues resulting from this phenomenon. Since the effects of expansive soil cannot be totally eliminated, homeowners should set realistic expectations regarding the performance of improvements constructed on this type of ground. This, along with good maintenance, can alleviate many issues. With the assistance of knowledgeable, competent design professionals and contractors, new improvements can be constructed to reduce the problems that will inevitably arise if expansive soil issues are not considered. You should consult such a professional, including a qualified geotechnical professional, in order to analyze the issues and properly design your improvements. 9 appendix design and ConstruCtion ideas for exterior improvements The following are some selected examples of measures that may help reduce the effects of expansive soil. Whether a particular idea or concept is right for your case will depend on many factors such as how expansive your soil is, who is doing the construction, your budget, aesthetics, and your expectations and tolerances related to the effects of expansive soil. Consult with a professional engineer, architect, and/or licensed contractor as well as your local building department when considering improvements on expansive soil. Patio and Pool Decks: Reinforcing steel bars within concrete slabs are generally recommended to strengthen the slabs against cracking if heave or settlement occurs. Such reinforcing as well as steel dowels (bars inserted across a joint where two distinct hard improvements join) can help to prevent both horizontal and vertical separations at joints and slab cracks. Control joints should also be used to allow separations along the joints rather than cracking within less desirable areas of slabs (less visual impact). Large continuous sections of flatwork should be avoided near top of slope areas. Planters, open areas, or other features should be provided between flatwork sections to accommodate lateral ground movement without significant visual impact. Steps may be constructed by overlapping slabs with a slip sheet between them rather than building all the steps as one interconnected feature. This can help to accommodate potential lateral movements and allow individual steps to move independently of other steps, thereby reducing the potential for unsightly cracks and separations. Consider using interlocking concrete paving stones (no grout) rather than concrete slabs for patio flatwork - or incorporate bands of these pavers between areas of concrete or other continuous decking. The pavers may shift when expansive soils move but can be reset and adjusted relatively easily if movements are more significant. Walls and Fences: Fencing such as wood or wrought iron which are more tolerant of movements may be considered. Connections to other hard surfaces such as other walls or structures (including the house) should be carefully thought out. Often, these connection points will be stress points as the walls moved by expansive soil forces. Purposely allowing for movements at these points can limit unsightly cracking or breakage. Special connections can be incorporated that allow for movements yet mask the visual effects of such movements (like slip joints). As mentioned in this guide, deeper foundations for walls (sometimes piles) may reduce the potential for leaning and tilting, especially near tops of slopes. However, some aesthetic impacts such as leaning and tilting should be anticipated. 10 Pools and Spas: Pools and spas near tops of slopes will tend to tilt and move laterally. The shells should be heavily reinforced and designed with expansive soil in mind. Consider using materials or tile patterns at the waterline that will mask the visual impact if the pool or spa shell tilts. As with other exterior structures, be careful when tying pools and spas into other hardscape. Design to accommodate movements and stressed at these points. Plumbing connections should be able to tolerate several inches of movement of the spa or pool. Shade Structures, Patio Covers and Elevated Decks/ Balconies: If such structures are attached to the house but also supported on the ground, the attached points should be designed to tolerate some movement of the structure if it is lifted or pulled by expansive soil forces. Alternatively, detaching the structure entirely from the house may avoid cracking of the area where the structure would have been attached. Consider tying column foundations together and also to the house foundation with buried concrete beams (grade beams) to resist the lateral movements. Alternatively, design columns and posts so they may be brought back to vertical if the foundations (bottoms) move laterally but the tops remained fixed. Outdoor Counters, BBQ Islands, Fireplaces, etc: These structures usually should have relatively stiff, isolated foundations. Since they will tend to move under the influence of soil, tile and stone work may crack or pop off if the structures are too flexible. Hard connections to other structures or hand improvements, such as the house or patio deck, pool coping, etc. should be avoided. Landscaping: Vegetation requiring less watering should be considered. Where more water loving varieties are planted, install liners and/or below ground collector drains in the planters to keep excess water from getting into deeper and/or surrounding expansive soil. Avoid constructing planters immediately adjacent to house foundations. Keep sprinklers away from foundations. Consider drip irrigation. Use automated irrigation system with timers that can be seasonally adjusted. Get professional advice tailored to your climate for recommended irrigation practices. Consider rain gauge monitored irrigation systems to prevent overwatering during the winter (home use products more recently have become available). Consider artificial grass. (New products are much more available than in years past).