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.
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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.
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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.
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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.
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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.
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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.
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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.
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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).