HomeMy WebLinkAboutPD 06-02; LUKAS RESIDENCE; FINAL SOILS REPORT; 2006-05-09FINAL REPAIR REPORT -
OBSERVATIONS AND COMPACTION TESTING
LUKAS RESIDENCE
7 626 Galleon Way
Carlsbad, California
May 9, 2006 File No. 23133.03
May 9, 2006
Ms. Shari Lukas
7626 Galleon Way
Carlsbad, California 92009
File No. 23133.03
Subject: FINAL REPAIR REPORT -OBSERVATIONS AND COMPACTION TESTING
LUKAS RESIDENCE
7626 Galleon Way
Carlsbad, California
References: "Limited Site Review, Lukas Residence, 7626 Galleon Way, Carlsbad, California,"
prepared by American Geotechnical, dated October 6, 2005, File No. 23133.0l
"Geotechnical Investigation, Slope Failure, Lukas Residence, 7626 Galleon Way,
Carlsbad, California," prepared by American Geotechnical, dated December 22, 2005,
File No. 23133.02
Dear Ms. Lukas:
In accordance with your request, we have performed observations and compaction testing during the
repair of your slope at 7626 Galleon Way, Carlsbad, California. Our prior work has consisted of a limited
site review and geotechnical investigation of the slope failure as referenced above.
Our recommended repair for the slope failure was to remove the failure mass and rebuild the failure
area by using layers of geogrid and compacted soil. In our opinion, the slope has been re-built in
conformance with our recommendations. By using stronger soil reinforced with geogrid, it is our opinion
that the repaired area of the slope has a factor of safety in excess of l .5. The slope has been essentially
re-built to its pre-failure condition.
We appreciate the opportunity to be of service. If you should have any questions, please do not
hesitate to contact us.
Sincerely,
AMERICAN GEOTECHNICAL
J? .Lr (,J. I)"'.)
Robert w. Day
Chief Engineer
R.C .E. 34544
G.E . 2059
RWD: kb
Distribution: Ms. Shari Lukas -(2) Via Mail Only
File No. 23133.03
May 9, 2006
Pagel
1.0 INTRODUCTION
1 . 1 Site Description
In our previous report dated October 6, 2005, we have provided details on the slope failure and
presented a photograph of the main slope failure. As indicated in that report, at the rear-yard
descending slope, we did observe two slope failures. One of the slope failures appears to have
been entirely on off-site property while the larger slope failure affected a portion of your property.
You indicated that the slope failures occurred in mid-March of 2005.
Based on our observation of the vertical displacement at the head scarp as well as the results of
our subsurface exploration, the depth of the slope failure was about 3 to 4 feet. Thus the slope
failure can be best described and classified as a shallow surface slip, also known as a surficial slope
failure.
The slope repair was performed in April 2006. The contractor who repaired the slope was Mr. Tony
Johnston of Vailson, Inc. American Geotechnical performed observations and compaction testing
during the repair of the slope.
1.2 Scope of Services
The scope of work performed during the slope repair included the following:
• Observations during the repair of the slope. Photographs were taken of observed
conditions and these photographs can be provided upon request.
Compaction testing of the fill placed during the re-building of the slope. The results of the
compaction tests are presented in Appendix A
• Laboratory testing of soil in order to determine the laboratory maximum dry density. This test
was needed in order to determine the relative compaction of the fill. The laboratory
maximum dry density test results are presented in Appendix B.
• Preparation of field reports. Copies of the field reports are presented in Appendix C .
• Preparation of this report.
File No. 23133.03
May 9, 2006
Page 2
2.0 REPAIR SEQUENCE
The slope failure located on the descending slope at the rear of the property has been repaired in
general conformance with our recommendations as outlined in our report dated December 22,
2005. During the repair of the slope, we performed site observations and compaction testing. Our
recommended repair for the slope failure was accomplished by removing the failure mass and
then rebuilding the failure area by using layers of geogrid and compacted fill . By using
compacted fill reinforced with geogrid, it is our opinion that the repaired area of the slope has a
factor of safety in excess of 1.5.
The specific steps in t he repair were as follows:
1. Site Preparation: The first step in the repair was to remove items from the slope failure area.
For example, the damaged irrigation system in the failure area was removed. Also, the top
of slope fence that was badly damaged was also removed. All of the ground cover (i.e.
vegetation) at the slope failure area was also removed and disposed of off-site.
2. Excavation of Key and Benches: A key was installed at the base of the slope failure.
Figure 1 shows the location of the key. The key was constructed directly adjacent the
drainage swale as shown in Figure 1. The width of the key was about 1 O feet. The bottom
of the key was over-excavated and re-compacted. We performed a compaction test (i.e.
Test No. 1, see Appendix A) on the re-compacted key bottom and the relative compaction
was90%.
During the excavation of the key, a corrugated metal drainage line was damaged. The
contractor replaced the damaged section of the drainage line. As the repair progressed
upslope, benches were cut into the hillside. During the benching operation, all of the slope
failure was removed.
File No. 23133.03
May 9, 2006
Page 3
3. Installation of Back-Drainage System: A back-drain system was installed at the back of the
key. The drain outlet was constructed such that it empties into the drainage swale. In
addition, the back-drain system included vertical chimney drains placed up the cut
benches of the back-cut and connected to a perforated drain line installed at the back of
the keyway.
4. Compacted Fill and Geogrid: As the slope was rebuilt, layers of geogrid were placed at a
vertical spacing of approximately 2 feet. A larger vertical spacing of the geogrid was
allowed because of the significantly g reater tensile strength of the geogrid that was used
for the repair. The fill (between the layers of geogrid) was compacted to a relative
compaction of at least 90% based on ASTM D 1557 (modified Proctor compaction test). We
performed field density tests in accordance with ASTM D 1556 (sand cone) and ASTM D
2922/3017 (nuclear density test).
5. Erosion Control and Rear Yard Drainage: After the slope failure area had been re-built,
erosion control matting was used to protect the slope face. A berm was constructed at the
top of slope so that surface water will flow away from the top of slope.
3.0 CLOSURE
This report has been prepared in accordance with generally accepted geotechnical engineering
principles and practices. The intent of this report is to advise our client on geotechnical matters
involving the site. The purpose of our work was to perform site observations and compaction
testing during the slope repair.
File No. 23133.03
Moy 9, 2006
Poge4
4.0 REFERENCES
American Geotechnical (2005). "Limited Site Review, Lukas Residence, 7626 Galleon Way,
Carlsbad, California," dated October 6, 2005, File No. 23133.0l.
American Geotechnical (2005). "Geotechnical Investigation, Slope Failure, Lukas Residence, 7626
Galleon Way, Carlsbad, California," dated December 22, 2005, File No. 23133.02
Day, R. W. (2006). Foundation Engineering: Design and Construction with the 2006 International
Building Code, Sponsored by ASCE and ICC, McGraw-Hill Book Company, l 000 pp.
Grading Plan, La Costa -South, Unit No. 7, Sheet 3 of 4 (portion of grading plan reproduce in
Figure 4).
Tan and Kennedy (l 996). Plate 2 -Geologic Map of the Encinitas and Rancho Santa Fe 7.5'
Quadrangles, San Diego County, California, CDMG Open-File Report 96-02.
APPENDIX A -COMPACTION TESTS
TEST Elevation Wet DRY MAXIMUM Relative MOISTURE Opt. DATE DENSITY NO. (ft) Density (pcf) DENSITY (pcf) Compact (%) Moisture
1 4/12/06 Key 125.4 105.6 116.5 90 18.7 13.0
2 4/17 /06 6' up 124.3 107.6 116.5 92 15.5 13.0
3 4/17 /06 6' up 125.7 108.4 116.5 93 15.8 13.0
4 4/18/06 10' up 122.5 107.1 116.5 92 14.3 13.0
5 4/18/06 10' up 123.8 107.8 116.5 92 14.9 13.0
6 4/18/06 11' up 122.8 105.6 116.5 91 16.3 13.0
7 4/19/06 15' up 124.2 105.2 116.5 90 18.1 13.0
8 4/19/06 15' up 125.0 106. l 116.5 91 17.9 13.0
9 4/21/06 18' up 114.8 105.6 116.5 91 8.7 13.0
10 4/21 /06 18' up 122.9 107.7 116.5 92 14.2 13.0
APPENDIX B -LABORATORY RESULTS
Laboratory Compaction Test
The laboratory compaction test was used to determine the maximum dry density of the fill. The test
was performed in accordance with ASTM D 1557. Test results are shown on the attached figure.
APPENDIX C -FIELD REPORTS