HomeMy WebLinkAboutCT 13-03; ROBERTSON RANCH- RANCHO COSTERA; PRELIMINARY PAVEMENT DESIGNS;Cl 1 0 7
LGC Valley, Inc.
Geotechnical Consulting
February 3, 2016 Project No. 133023-03
Mr. Kevin Brickley
Toll Brothers, Inc.
725 W. Town and Country Road, Suite 200
Orange, California 92868
Subject: Preliminary Pavement Design for Portola Court and a Portion of Wellspring Street,
Glasgow Drive, and Nelson Court, Robertson Ranch, Carlsbad Tract No. 13-03, 4980 El
Camino Real, Carlsbad, California
References: Carlsbad, City of 2012, Engineering Standards, Volume 1 - General Design Standards,
Carlsbad, California, 2004 Edition, revised November 21, 2012
O'Day Consultants, 2015, Improvement Plans for Rancho Costera, Robertson Ranch
West Village, Carlsbad Tract No. 13-03, Carlsbad, California, Drawing No. 480-3,
100 Sheets, dated July 21, 2015
Introduction
In accordance with your authorization, LGC Valley, Inc. (LGC) has been performing geotechnical
observation and testing services during the development of the Robertson Ranch project located in
Carlsbad, California. This letter has been prepared in accordance with the requirements of the City of
Carlsbad and provides pavement design recommendations for the third phase of street construction within
Robertson Ranch. The streets within Phase 3 include: Portola Court Station No. 9+60 to 15+30; Nelson
Court Station 9+60 to 13+50; Wellspring Street Station No. 10+35 to 23+70; and Glasgow Drive Station
No. 11+45 to 30+65.
Seven representative subgrade soil samples were obtained along the subject roadway alignments. The
samples were transported to the laboratory and R-value testing (in accordance with Caltrans Test Method
301) was performed. The test results of the R-value testing indicated the subgrade soils have R-values
ranging from 16to 32. The approximate sample locations and results of the laboratory testing are presented
in Table 1.
Based on the project improvement plans (O'Day Consultants, 2015) and the city requirements (Carlsbad,
2012) we understand that:
Portola Court between Station No. 12+25 and 15+30, Wellspring Street, and Glasgow Drive (i.e. 60-
foot wide residential streets) have a TI of 6.0 and a minimum pavement section of 4 inches of AC
over 6 inches of AB; and,
Portola Court between Station No. 9+60 and 12+25 and Nelson Court between Station 9+60 and
13+50 (i.e. 56-foot wide cul-de-sac streets) have a TI of 4.5 and a minimum pavement section of 4
inches of AC over 4 inches of AB.
2420 Grand Avenue, Suite F2, 9 Vista 9 CA 92081 • (760) 599-7000 • Fax (760) 599-7007
Laboratory R- Value TestinR
Representative Street subgrade soils were collected and R-value testing was performed on the samples. The
resistance or "R"-value was determined by the California Materials Method No. 301 for subgrade soils. The
test results are summarized in the Table 1.
Table 1
R-Value Test Results
Sample
Number Sample Location Sample Description R-Value
R-1 Nelson Court Station No. 11+00 Light gray brown clayey fine SAND
to clayey sandy SILT 26
R-2 Portola Court Station No. 13+75 Light gray brown clayey fine SAND
to clayey sandy SILT 16
R-3 Glasgow Drive Station No. 15+00 Light gray brown silty fine SAND 25
R-4 Glasgow Drive Station No. 21+50 Light gray brown silty fine SAND 32
R-5 Glasgow Drive Station No. 27+00 Light gray brown silty fine SAND 29
R-6 Wellspring Street Station No. 14+50 Light gray brown silty fine SAND 25
R-7 Wellspring Street Station No. 19+00 Light gray brown silty fine SAND 25
Pavement flesiRn Recommendations
Based on the Traffic Indices and the R-value test results presented above, the asphalt concrete over
aggregate base pavement sections were calculated using the computer program, NEWCON90 and in
accordance with Chapter 600 of the California Highway Design Manual. The designs were then compared
with the City of Carlsbad's minimum section thickness requirements and revised as necessary. The
pavement sections are presented on Table 2.
I
Project No. 133023-03 Page 2 February 3, 2016
Table 2
Recommended Pavement Sections Utilizing Aggregate Base
Asphalt Aggregate
Street Traffic Design Concrete Base
Index R-Value Thickness Thickness
(inches) (inches)
Portola Court Sta. 9+60 to 12+25 and
Nelson Court Sta. 9+60 to 13+50 4.5 14 4.0 5.0
Portola Court Sta. 12+25 to 15+30 6.0 14 4.0 9.5
Glasgow Sta. 11+45 to 30+65 and 6.0 25 4.0 8.0 Wellspring Street Sta. 10+35 to 23+70
Prior to placement of the street aggregate base material, the upper 12 inches of subgrade soils in the street
(including beneath the curb and gutter) shall be scarified, moisture-conditioned (or dried back) as necessary to
at least optimum moisture content and compacted to a minimum 95 percent relative compaction based on
American Standard of Testing and Materials (ASTM) Test Method D1557.
Caltrans Class 2 Aggregate Base (Class 2 AB) or Greenbook Crushed Miscellaneous Base (CMB) shall then
be placed and compacted at a minimum 95 percent relative compaction in accordance with ASTM Test
Method D1557. The aggregate base material can be a maximum of 6 inches thick (or equal to the thickness of
the aggregate base for the design pavement section if less than 6 inches) below the curb and gutter and extend
a minimum of 6 inches behind the back of the curb (per the city requirements). The aggregate base shall
conform to and be placed in accordance with the latest revision of the California Department of
Transportation Standard Specifications (Section 26), the "Greenbook" Standard Specifications for Public
Works Construction specifications, and/or the City of Carlsbad requirements. Asphalt Concrete shall conform
to and be placed in accordance with the "Greenbook" Standard Specifications for Public Works Construction
and the City of Carlsbad requirements.
If pavement is planned adjacent to landscaped areas, we recommend that appropriate measures be taken (such
as keeping the amount of landscape irrigation to a minimum, installing area drains or other devices, etc.) to
reduce the possible adverse effects of water on the pavement subgrade.
Limitations
Our services were performed using the degree of care and skill ordinarily exercised, under similar
circumstances, by reputable engineers, and geologists practicing in this or similar localities. No other
warranty, expressed or implied, is made as to the conclusions and professional advice included in this letter
report.
Project No. 133023-03 Page 3 February 3, 2016
This letter report is issued with the understanding that it is the responsibility of the owner, or of his/her
representative, to ensure that the information and recommendations contained herein are brought to the
attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are
taken to see that the contractor and/or subcontractor properly implements the recommendations in the field.
The contractor and/or subcontractor should notify the owner if they consider any of the recommendations
presented herein to be unsafe.
The findings of this report are valid as of the present date. However, changes in the conditions of a property
can and do occur with the passage of time, whether they be due to natural processes or the works of man on
this or adjacent properties.
Closure
If you should have any questions, please do not hesitate to contact us. The undersigned can be reached at
(760) 599-7000 or (661) 702-8474.
Respectfully submitted,
LGC Valley, Inc.
O~wt'~'
Randall Wagner, CEG 1612
Senior Project Geologist
RKW/BIH
900-
Basil Hattar, GE 2734
Principal Engineer
Distribution: (1) Addressee (via e-mail)
(2) City of Carlsbad
Attention: Mr. Grant Clavier
Project No. 133023-03 Page 4 February 3, 2016
LGC Valley, Inc.
Geotechnical Consulting
November 20, 2015
Mr. Kevin Brickley
Toll Brothers, Inc.
725 W. Town and Country Road, Suite 200
Orange, California 92868
Project No. 133023-03
Subject: Preliminary Pavement Design for La Paz Court and a Portion of Robertson Road,
Wellspring Street, Glasgow Drive, and Nelson Court, Robertson Ranch, Carlsbad Tract
No. 13-03, 4980 El Camino Real, Carlsbad, California
References: Carlsbad, City of 2012, Engineering Standards, Volume 1 - General Design Standards,
Carlsbad, California, 2004 Edition, revised November 21, 2012
LGC Valley, 2015, Preliminary Pavement Design for Trailblazer Way, West Ranch
Street, and a Portion of Robertson Road, Wellspring Street, and Nelson Court, Robertson
Ranch, Carlsbad Tract No. 13-03, 4980 El Camino Real, Carlsbad, California, Project
No. 133023-03, dated November 3, 2015 (revised November 10, 2015)
O'Day Consultants, 2015, Improvement Plans for Rancho Costera, Robertson Ranch
West Village, Carlsbad Tract No. 13-03, Carlsbad, California, Drawing No. 480-3,
100 Sheets, dated July 21, 2015
Introduction
In accordance with your authorization, LGC Valley, Inc. (LGC) has been performing geotechnical
observation and testing services during the development of the Robertson Ranch project located in
Carlsbad, California. This letter has been prepared in accordance with the requirements of the City of
Carlsbad and provides pavement design recommendations for the second phase of street construction
within Robertson Ranch. The streets within Phase 2 include: La Paz Court Station No. 9+55 to 17+08;
Wellspring Street Station No. 28+50 to 30+68; Robertson Road Station No. 10+40 to 17+00; and Glasgow
Drive Station No. 31+50 to 35+80 and 36+30 to 38+00.
Three additional representative subgrade soil samples were obtained along the subject roadway alignments
to supplement previous R-Value testing. The samples were transported to the laboratory and R-value
testing (in accordance with Caltrans Test Method 301) was performed. The test results of the applicable
previous and additional R-value testing indicated the subgrade soils have R-values ranging from 9 to 14 for
these portions of the subject streets. The approximate sample locations and results of the laboratory testing
are presented in Table 1. It should be noted that for subgrade samples with an R-value of less than 12, the
City of Carlsbad requires further testing with lime and an engineering evaluation for the potential
implementation of a lime-treated pavement section.
Based on the project improvement plans (O'Day Consultants, 2015) and the city requirements (Carlsbad,
2012) we understand that:
2420 Grand Avenue, Suite F2, 9 Vista • CA 92081 • (760) 599-7000 • Fax (760) 599-7007
Robertson Road between Station No. 10+40 and 17+00, Wellspring Street, Glasgow Drive, and La Paz
Court between Station No. 13+50 and 17+08 (i.e. 60-foot wide residential streets) have a TI of 6.0
and a minimum pavement section of 4 inches of AC over 6 inches of AB; and,
La Paz Court between Station No. 9+55 and 13+50 (i.e. a 56-foot wide cul-de-sac street) has a TI of
4.5 and a minimum pavement section of 4 inches of AC over 4 inches of AB.
Laboratory R- Value TestinR
Representative street subgrade soils were collected, at four locations within the portion of the subject streets
included in this report, and R-value testing was performed on the samples. The resistance or "R"-value was
determined by the California Materials Method No. 301 for subgrade soils. The test results are summarized in
the Table 1.
Table 1
R-Value Test Results
Sample Number Sample Location Sample Description R-Value
Robertson Road,
Station No. 12+50 Light gray brown fine
R-1 10
(Representative of Robertson Road Station clayey SILT
No. 10+40 to 17+00)
La Paz Court,
R-2 Station No. 11+50 Light gray fme sandy to 13
(Representative of La Paz Court Station No. clayey SILT
9+55 to 13+50)
La Paz Court,
Station No. 16+25 Light gray brown fine R-3 9 (Representative of Glasgow Drive Station No. clayey SILT 36+30 to 38+00, La Paz 13+50 to 17+08, and
Wellspring Street 28+50 to 30+68)
Nelson Court,
R.4* Station No. 15+50 Light gray fine sandy to 14
(Representative of Glasgow Drive Station No. clayey SILT
31+50 to 35+80)
R-Value testing of representative soils previously submitted in the first pavement section
recommendation letter dated November 10, 2015 (LGC Valley, 2015).
Project No. 133023-03 Page 2 November 20, 2015
Pavement Desi'n Recommendations
Based on the Traffic Indices and the R-value test results presented above, the asphalt concrete over
aggregate base pavement sections were calculated using the computer program, NEWCON90 and in
accordance with Chapter 600 of the California Highway Design Manual. The designs were then compared
with the City of Carlsbad's minimum section thickness requirements and revised as necessary. The
pavement sections are presented on Table 2.
Table 2
Recommended Pavement Sections Utilizing Aggregate Base
Asphalt Aggregate
Street Traffic Design Concrete Base
Index R-Value Thickness Thickness
(inches) (inches)
Robertson Road (Sta. 10+40 to 13+05) 6.0 10 4.0 10.5
Glasgow Drive (Sta. 31+50 to 35+80) 6.0 14 4.0 9.5
Glasgow Drive (Sta. 36+30 to 38+00), La
Paz Court (Sta. 13+50 to 17+08), and 6.0 9 4.0 11.0
Wellspring Street (Sta. 28+50 to 30+68)
La Paz Court (Sta. 9+55 to 13+50) 4.5 9 4.0 5.0
Prior to placement of the street aggregate base material, the upper 12 inches of subgrade soils in the street
(including beneath the curb and gutter) shall be scarified, moisture-conditioned (or dried back) as necessary to
at least optimum moisture content and compacted to a minimum 95 percent relative compaction based on
American Standard of Testing and Materials (ASTM) Test Method Dl 557.
Caltrans Class 2 Aggregate Base (Class 2 AB) or Greenbook Crushed Miscellaneous Base (CMB) shall then
be placed and compacted at a minimum 95 percent relative compaction in accordance with ASTM Test
Method D1557. The aggregate base material can be a maximum of 6 inches thick (or equal to the thickness of
the aggregate base for the design pavement section if less than 6 inches) below the curb and gutter and extend
a minimum of 6 inches behind the back of the. curb (per the city requirements). The aggregate base shall
conform to and be placed in accordance with the latest revision of the California Department of
Transportation Standard Specifications (Section 26), the "Greenbook" Standard Specifications for Public
Works Construction specifications, and/or the City of Carlsbad requirements. Asphalt Concrete shall conform
to and be placed in accordance with the "Greenbook" Standard Specifications for Public Works Construction
and the City of Carlsbad requirements.
If pavement is planned adjacent to landscaped areas, we recommend that appropriate measures be taken (such
as keeping the amount of landscape irrigation to a minimum, installing area drains or other devices, etc.) to
reduce the possible adverse effects of water on the pavement subgrade.
Project No. 133023-03 Page 3 November 20, 2015
Pavement Design Sections Utilizin2 Lime-Treated Subgrade Soils
The following pavement design recommendations utilizing a lime-treated subgrade section are provided in
accordance with the City of Carlsbad guidelines. A previous soil sample representative of the onsite soils
having a R-value of less than 12 was tested for optimum lime content (per ASTM Test Method C977). The
test result indicated that the optimum lime content was determined to be 5-percent quick lime. After the lime
was added to the sample and allowed to cure a minimum of 24 hours, testing of the lime-treated sample
resulted in an R-value of 60.
Based on the above information, the preliminary lime-treated pavement sections were calculated using the
computer program, NEWCON90 and in accordance with Chapter 600 of the California Highway Design
Manual; compared with the City of Carlsbad's minimum section thickness requirements. The lime-treated
pavement sections are presented on Table 3.
Table 3
Recommended Pavement Sections Utilizing Lime-Treated Subgrade Soils
Asphalt Aggregate Lime-
Treated
Street Traffic Design Concrete Base Subgrade Index R-Value Thickness Thickness Layer (inches) (inches) (inches)
Robertson Road
(Sta. 10+40 to 13+05)
Glasgow Drive
(Sta. 36+30 to 38+00), 6.0 60 4.0 6.0 8.0 La Paz Court
(Sta. 13+50 to 17+08), and
Wellspring Street
(Sta. 28+50 to 30+68)
La Paz Court
(Sta. 9+55 to 13+50) 4.5 60 4.0 4.0 8.0
Prior to the placement of the asphalt concrete and the Caltrans Class 2 Aggregate Base or Crushed
Miscellaneous Base material, the subgrade soils (including beneath the curb and gutter) shall be scarified,
moisture-conditioned to at least optimum moisture content, and thoroughly mixed with 5-percent quick lime
(or an equivalent percentage of hydrated lime-slurry) to the depth recommended in Table 3. After setting for a
minimum of 24 hours, the thoroughly mixed lime-treated subgrade soils shall be compacted to a minimum 95
percent relative compaction based on ASTM Test Method D1557.Once the minimum 95 percent relative
compaction is achieved for the lime-treated subgrade soils, we recommend that a curing compound be applied
to the surface of the lime-treated subgrade soils and/or the water to applied to the soils to keep them moisture-
conditioned, and the soils allowed to cure.
Project No. 133023-03 Page 4 November 20, 2015
After the completion of the curing period, the aggregate base shall then be placed and compacted at a
minimum 95 percent relative compaction in accordance with ASTM Test Method Dl 557. The aggregate base
material shall extend below the curb and gutter and extend a minimum of 6 inches behind the back of the
curb. After the placement and compaction of the aggregate base, a minimum of 4 inches of asphalt concrete
shall be placed, per the design section.
Asphalt concrete, aggregate base, and lime-treated subgrade soils shall conform to and be placed in
accordance with: 1) the latest revision of the California Department of Transportation Standard
Specifications; 2) the State of the Art Report 5, Lime Stabilization of the Transportation Research Board,
National Research Council; 3) the "Greenbook" Standard Specifications for Public Works Construction
(Sections 203 and/or 400); and/or 4) the City of Carlsbad requirements.
Portland Cement Concrete (FCC) Pavement Section for Robertson Road Station 13+05 to 17+00
The gradient of a portion of Robertson Road between Stations 13+05 to 17+00 is greater than 10 percent; and
consequently, the street pavement section is required to be a Portland Cement Concrete (PCC) pavement
section (per City of Carlsbad criteria). Based on an R-Value of 10 and a TI of 6, we recommend a minimum
of 8-inches of PCC over 6-inches of compacted aggregate base. The modulus of rupture of the concrete
should be a minimum of 500 pounds per square inch (psi) at 28 days. Contraction joints should be placed at
maximum 15-foot spacings. Where the outer edge of the concrete pavement connects to an asphalt pavement,
the concrete slab should be thickened by 50 percent at a taper not to exceed a slope of 1 in 10.
The aggregate base shall conform to the requirements of the latest edition of the California Department of
Transportation Standard Specifications and/or the Standard Specifications for Public Works Construction
("Greenbook"). Aggregate base shall be compacted to a minimum of 95 percent relative compaction over
subgrade compacted to a minimum of 95 percent relative compaction per ASTM- D15 57.
Limitations
Our services were performed using the degree of care and skill ordinarily exercised, under similar
circumstances, by reputable engineers and geologists practicing in this or similar localities. No other
warranty, expressed or implied, is made as to the conclusions and professional advice included in this letter
report.
This letter report is issued with the understanding that it is the responsibility of the owner, or of his/her
representative, to ensure that the information and recommendations contained herein are brought to the
attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are
taken to see that the contractor and/or subcontractor properly implements the recommendations in the field.
The contractor and/or subcontractor should notify the owner if they consider any of the recommendations
presented herein to be unsafe.
The findings of this report are valid as of the present date. However, changes in the conditions of a property
can and do occur with the passage of time, whether they be due to natural processes or the works of man on
this or adjacent properties.
Project No. 133023-03 Page 5 November 20, 2015
Closure
If you should have any questions, please do not hesitate to contact us. The undersigned can be reached at
(760) 599-7000 or (661) 702-8474.
Respectfully submitted,
LGC Valley, Inc.
_Owq-~'
Randall Wagner, CEO 1612
Senior Project Geologist
94-
Basil Hattar, GE 2734
Principal Engineer
Distribution: (1) Addressee (via e-mail)
(2) City of Carlsbad
Attention: Mr. Grant Clavier
Project No. 133023-03 Page 6 November 20, 2015
LGC Valley, Inc.
Geotechnical Consulting
November 3, 2015 Project No. 133023-03
Mr. Kevin Brickley
Toll Brothers, Inc.
725 W. Town and Country Road, Suite 200
Orange, California 92868
Subject: Preliminary Pavement Design for Trailblazer Way, West Ranch Street, and a Portion of
Robertson Road, Wellspring Street, and Nelson Court, Robertson Ranch, Carlsbad Tract
No. 13-03, 4980 El Camino Real, Carlsbad, California
References: Carlsbad, City of 2012, Engineering Standards, Volume 1 - General Design Standards,
Carlsbad, California, 2004 Edition, revised November 21, 2012
O'Day Consultants, 2015, Improvement Plans for Rancho Costera, Robertson Ranch
West Village, Carlsbad Tract No. 13-03, Carlsbad, California, Drawing No. 480-3,
100 Sheets, dated July 21, 2015
Introduction
In accordance with your authorization, LGC Valley, Inc. (LGC) has been performing geotechnical
observation and testing services during the development of the Robertson Ranch project located in
Carlsbad, California. This letter has been prepared in accordance with the requirements of the City of
Carlsbad and provides pavement design recommendations for the first phase of street construction within
Robertson Ranch, located in Carlsbad, California. The streets within Phase 1 include Trailblazer Way;
West Ranch Street; Robertson Road Station No. 17+00 to 34+45; Wellspring Street Station No. 23+70 to
28+00; and Nelson Court Station No. 13+65 to 17+00.
Eight representative subgrade soil samples were obtained along the roadway alignments. The samples were
transported to a laboratory and R-value testing (in accordance with Caltrans Test Method 301) was
performed. The test results indicated the subgrade soils have R-values ranging from 10 to 28. The
approximate sample locations and results of the laboratory testing are presented in Table 1. It should be
noted that for subgrade samples with an R-value of less than 12, the City of Carlsbad requires further
testing with lime and an engineering evaluation for the potential implementation of a lime-treated pavement
section. Based on the project improvement plans (O'Day Consultants, 2015) and the city requirements
(Carlsbad, 2012) we understand that:
West Ranch Street has a Traffic Index (TI) of 8.5 and a minimum pavement section of 5 inches of
Asphalt Concrete (AC) over 6 inches of Aggregate Base (AB);
Robertson Road between Station No. 27+00 and 34+45 (i.e. a 60-foot wide collector street) has a TI of
6.0 and a minimum pavement section of 4 inches of AC over 6 inches of AB;
Robertson Road between Station No. 17+00 and 27+00, Wellspring Street, and Nelson Court (i.e. 60-
foot wide residential streets) have a TI of 6.0 and a minimum pavement section of 4 inches of AC
over 6 inches of AB; and,
Trailblazer Way (i.e. a 56-foot wide cul-de-sac street) has a TI of 4.5 and a minimum pavement section
of 4 inches of AC over 4 inches of AB.
2420 Grand Avenue, Suite F2, • Vista 9 CA 92081 • (760) 599-7000. Fax (760) 599.7007
Laboratory R- Value Testing
Representative street subgrade soils were collected, at eight locations across the site, and R-value testing was
performed on the samples. The resistance or "R"-value was determined by the California Materials Method
No. 301 for subgrade soils. The test results summarized in the Table 1.
Table 1
R-Value Test Results
Sample Number Sample Location Sample Description R-Value
R-1 Trailblazer Way, Gray brown fine sandy 10 Station No. 8+50 silty CLAY
R-2 West Ranch, Light gray brown silty fine 27 Station No. 17+75 SAND
R-3 West Ranch, Light gray brown clayey to 12 Station No. 12+50 silty fine SAND
R-4 Robertson Road, Light gray fine sandy to 18 Station No. 22+00 clayey SILT
R-5 Robertson Road, Light gray fine sandy to 20 Station No. 26+50 clayey SILT
R-6 Robertson Road, Light gray silty fine 26 Station No. 30+25 SAND
R-7 Wellspring Street, Light gray silty fine 28 Station No. 24+00 SAND
R-8 Nelson Court, Light gray fine sandy to 14 Station No. 15+50 clayey SILT
Pavement Design Recommendations
Based on the Traffic Indices and the R-Value test results presented above, the asphalt concrete over
aggregate base pavement sections were calculated using the computer program, NEWCON90 and in
accordance with Chapter 600 of the California Highway Design Manual. The designs were then compared
with the City of Carlsbad's minimum section thickness requirements and revised as necessary. The
pavement sections are presented on Table 2.
Project No. 133023-03 Page 2 November 3, 2015
Table 2
Recommended Pavement Sections Utilizing Aggregate Base
Asphalt Aggregate
Street Traffic Design Concrete Base
Index R-Value Thickness Thickness
(inches) (inches)
West Ranch Street 8.5 12 5.0 17.0
Robertson Road (Sta. 17+00 to 34+25) 6.0 18 4.0 9.0
Wellspring Street (Sta. 23+70 to 28+00) 6.0 28 4.0 7.0
Nelson Court (Sta. 13+65 to 17+00) 6.0 14 4.0 9.5
Trailblazer Way 4.5 10 4.0 5.0
Prior to placement of the street aggregate base material, the upper 12 inches of subgrade soils in the street
(including beneath the curb and gutter) should be scarified, moisture-conditioned (or dried back) as necessary
to at least optimum moisture content and compacted to a minimum 95 percent relative compaction based on
American Standard of Testing and Materials (ASTM) Test Method D1557.
Caltrans Class 2 Aggregate Base (Class 2 AB) or Greenbook Crushed Miscellaneous Base (CMB) should
then be placed and compacted at a minimum 95 percent relative compaction in accordance with ASTM Test
Method D1557. The aggregate base material can be a maximum of 6 inches thick (or equal to the thickness of
the aggregate base for the design pavement section if less than 6 inches) below the curb and gutter and extend
a minimum of 6 inches behind the back of the curb (per the city requirements). The aggregate base should
conform to and be placed in accordance with the latest revision of the California Department of
Transportation Standard Specifications (Section 26), the "Greenbook" Standard Specifications for Public
Works Construction specifications, and/or the City of Carlsbad requirements. Asphalt Concrete should
conform to and be placed in accordance with the "Greenbook" Standard Specifications for Public Works
Construction and the City of Carlsbad requirements.
If pavement is planned adjacent to landscaped areas, we recommend that appropriate measures be taken (such
as keeping the amount of landscape irrigation to a minimum, installing area drains or other devices, etc.) to
reduce the possible adverse effects of water on the pavement subgrade.
Project No. 133023-03 Page 3 November 3, 2015
Pavement Design Sections Utilizing Lime-Treated SubRrade Soils
The following pavement design recommendations utilizing a lime-treated subgrade section are provided in
accordance with the City of Carlsbad guidelines. A previous soil sample representative of the onsite soils
having a R-value of less than 12 was tested for optimum lime content (per ASTM Test Method C977).
The test result indicated that the optimum lime content was determined to be 5-percent quick lime. After
the lime was added to the sample and allowed to cure a minimum of 24 hours, testing of the lime-treated
sample resulted in a minimum R-value of 60.
Based on the above information, the preliminary lime-treated pavement sections were calculated using the
computer program, NEWCON90 and in accordance with Chapter 600 of the California Highway Design
Manual; compared with the City of Carlsbad's minimum section thickness requirements. The lime-treated
pavement sections are presented on Table 3.
Table 3
Recommended Pavement Sections Utilizing Lime-Treated Subgrade Soils
Asphalt Aggregate Lime-
Street Traffic Design Concrete Base Treated
Subgrade Index R-Value Thickness Thickness
(inches) (inches) Layer (inches)
West Ranch Street 8.5 60 5.0 6.0 11.0 (Sta. 10+50 to 19+30)
Robertson Road 6.0 60 4.0 6.0 8.0 (Sta. 17+00 to 34+25)
Trailblazer Way 4.5 60 4.0 4.0 8.0
Prior to the placement of the asphalt concrete and the Caltrans Class 2 Aggregate Base or Crushed
Miscellaneous Base material, the subgrade soils (including beneath the curb and gutter) should be scarified,
moisture-conditioned to at least optimum moisture content, and thoroughly mixed with 5-percent quick lime
(or an equivalent percentage of hydrated lime-slurry) to the depth recommended in Table 3. After setting for a
minimum of 24 hours, the thoroughly mixed lime-treated subgrade soils should be compacted to a minimum
95 percent relative compaction based on ASTM Test Method D1557.Once the minimum 95 percent relative
compaction is achieved for the lime-treated subgrade soils, we recommend that a curing compound be applied
to the surface of the lime-treated subgrade soils and/or the water to applied to the soils to keep them moisture-
conditioned, and the soils allowed to cure.
After the completion of the curing period, the aggregate base should then be placed and compacted at a
minimum 95 percent relative compaction in accordance with ASTM Test Method D1557. The aggregate base
material should extend below the curb and gutter and extend a minimum of 6 inches behind the back of the
curb. After the placement and compaction of the aggregate base, a minimum of 4 or 5 inches of asphalt
concrete should be placed, per the design section.
Project No. 133023-03 Page 4 November 3, 2015
Asphalt Concrete, Aggregate Base, and lime-treated subgrade soils should conform to and be placed in
accordance with: 1) the latest revision of the California Department of Transportation Standard
Specifications; 2) the State of the Art Report 5, Lime Stabilization of the Transportation Research Board,
National Research Council; 3) the "Greenbook" Standard Specifications for Public Works Construction
(Sections 203 and/or 400); and/or 4) the City of Carlsbad requirements.
Limitations
Our services were performed using the degree of care and skill ordinarily exercised, under similar
circumstances, by reputable engineers and geologists practicing in this or similar localities. No other
warranty, expressed or implied, is made as to the conclusions and professional advice included in this letter
report.
This letter report is issued with the understanding that it is the responsibility of the owner, or of his/her
representative, to ensure that the information and recommendations contained herein are brought to the
attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are
taken to see that the contractor and/or subcontractor properly implements the recommendations in the field.
The contractor and/or subcontractor should notify the owner if they consider any of the recommendations
presented herein to be unsafe.
The findings of this report are valid as of the present date. However, changes in the conditions of a property
can and do occur with the passage of time, whether they be due to natural processes or the works of man on
this or adjacent properties.
Closure
If you should have any questions, please do not hesitate to contact us. The undersigned can be reached at
(661) 702-8474.
Respectfully submitted,
LGC Valley, Inc.
owx~'
Randall Wagner, CEG 1612
Senior Project Geologist
RKW/BIH
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47 No. 16t2 0. CP.1iF1E0 3 - (JEERIUG : GEGLOGST
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OPC 94-
Basil Hattar, GE 2734
Principal Engineer
Distribution: (1) Addressee (via e-mail)
(2) City of Carlsbad
Attention: Mr. Grant Clavier
Project No. 133023-03 Page 5 November 3, 2015