ADDENDUM NO. 1 - Chaffey College · Readings were taken in the core explorations using a dual-mass dynamic cone penetrometer in accordance with ASTM D6951. The tip of the probe was

Official Copy for Informal Bid No. 2019PW682 1 of 2 Addendum No. 1, May 22, 2019

ADDENDUM NO. 1

BID AND CONTRACT DOCUMENTS

FOR

INFORMAL BID No. 2019PW682

CHAFFEY COMMUNITY COLLEGE DISTRICT COLLEGE DRIVE EAST REPAIR

RANCHO CUCAMONGA, CALIFORNIA COUNTY OF SAN BERNARDINO

CHAFFEY COMMUNITY COLLEGE DISTRICT 5885 Haven Avenue

Rancho Cucamonga, CA 91737

Official Copy for Informal Bid No. 2019PW682 2 of 2 Addendum No. 1, May 22, 2019

The following changes, additions, deletions, clarifications, or corrections shall become part of the Bid and Contract Documents for Chaffey Community College District Informal Bid No. 2019PW682, College Drive East Repair Project at the Rancho Cucamonga Campus, first detailed in the IFB dated May 8, 2019. All other terms, specifications, and conditions remain the same. Each bidder is responsible for transmitting this information to all affected subcontractors and suppliers prior to the receipt of bids. Each bidder shall acknowledge receipt of this Addendum on its Bid Form. Modifications are identified by “clouds” and the following: Deletions strikethrough

Insertions/Substitutions italic-underlined.

ITEM No. 1: ADD the CONTRACTORS QUESTIONS & ANSWERS Item No. AD-1.1 / RFC #2019PW682-1 Question: Construction note 11 on Plan sheet C2.1 indicates using CAB. At the job walk, it was mentioned that recycled base material was acceptable for use. Is CAB required for this project or is crushed miscellaneous base (CMB) an approved material to use for this project? Answer: CMB will be allowed, provided that it meets the quality requirement of Section 200-2.4 of the Greenbook. Item No. AD-1.2 / RFC #2019PW682-2 Question: In the specifications, 32 12 16 sections 2.02 (A) as well as 3.04 (A), it calls for a SC – 250 Prime Coat to be applied on the compacted subgrade. Prime coat is typically not used in California; is prime coat required for this project? Answer: Prime coat can be eliminated. ITEM No. 2; CONTRACT DOCUMENTS 1. ADD Geotechnical Pavement Investigation for College Drive - Omnitrans Transit Center to

Panther Drive dated April 16, 2019 (14 pages).

END OF ADDENDUM NO. 1 INCLUDING REFERENCED ENCLOSURE Enclosure: 1. Geotechnical Pavement Investigation for College Drive - Omnitrans Transit Center to

Panther Drive dated April 16, 2019 (14 pages).

2015 West Park Avnue, Unit 1 ■ Redlands, California 92374 ■ Telephone 909.894.2175

Project No. T2746-99-08

April 16, 2019

Chaffey College

5585 Haven Avenue

Rancho Cucamonga, California 91737

Attention: Ms. Sarah Riley, Facilities Development

Subject: GEOTECHNICAL PAVEMENT INVESTIGATION

COLLEGE DRIVE

OMNITRANS TRANSIT CENTER TO PANTHER DRIVE

CHAFFEY COLLEGE

RANCHO CUCAMONGA, CALIFORNIA

Dear Ms. Riley:

In accordance with our March 19, 2019 proposal and your March 19, 2019 notice to proceed, Geocon

West, Inc. (Geocon) has prepared this letter report of our pavement investigation for College Drive at

Chaffey College in Rancho Cucamonga, California (see Vicinity Map, Figure 1). This letter presents a

summary of the methods used to core the road, existing pavement section thicknesses, results of the

laboratory testing, and our recommendations for rehabilitation of the roadway.

PROJECT UNDERSTANDING

Chaffey College is rehabilitating College Drive at their Rancho Cucamonga campus between the

Omnitrans Transit Center and Panther Drive. The approximate extent of the planned rehabilitation is

shown on Figure 2, Coring Location Map. We understand that Chaffey College plans to remove the

existing paving and replace it with a new asphalt concrete wearing surface. College Drive is one of the

main roadways through Chaffey College and supports passenger cars, busses, and maintenance vehicles.

We understand from our discussions with Valued Engineering that the estimated Traffic Index (TI) for

the roadway will be between 8 and 9.

At the time of our investigation, portions of the pavement surface for the existing street are moderately to

severely distressed. Observed pavement distress generally consists of longitudinal cracking, transverse

cracking, alligator cracking, edge cracking, patching, raveling, and weathering. The western side of

College Drive in the area of Parking Lot 7 has been recently repaved as part of the construction of the

Campus Center East Plaza project. Additionally, two areas within the southbound lane were covered

with steel plates at the time of our field work as part of a utility repair.

Geocon Project No. T2746-99-08 - 2 - April 16, 2019

The purpose of the investigation was to observe the surficial pavement conditions, core the existing

pavement sections to measure the asphalt concrete and aggregate base thickness and perform dynamic

cone penetrometer testing of the underlying subgrade. The recommendations presented herein are

based on site observations, analysis of the data obtained during the investigation, and our experience

with similar soil and geologic conditions. If project details vary significantly from those described

herein, Geocon should be contacted to determine the necessity for review and possible revision of this

report.

SCOPE OF SERVICES

Our scope of services included the following:

• Perform reconnaissance of the site to document existing pavement conditions.

• Meet with college personal to cite core locations.

• Mark the proposed core locations and notify Underground Service Alert (USA) to locate and

mark utilities in the proposed investigation area.

• Excavate cores in the road. The existing pavement structural section thicknesses were

measured and bulk samples were collected from the subgrade.

• Perform dynamic cone penetrometer testing of the exposed soils.

• Perform laboratory testing including resistance value (R-value) and grain size distribution of

subgrade soil, and asphalt content and aggregate gradation of existing asphaltic concrete

pavements.

• Prepare this written report presenting our findings, conclusions and recommendations.

PAVEMENT CORING AND LABORATORY TESTING

Coring of College Drive was performed on March 29th, 2019. The approximate core locations are

shown on the Coring Location Map (see Figures 2). The core samples were obtained using a 6-inch

diameter diamond core barrel. The cores were drilled through the asphalt concrete, and the and into the

subgrade using hand excavation tools. Measurements of the existing pavement structural section layers

were taken in the field, and samples of the subgrade were collected for laboratory testing. The cores

and soil samples were transported to our geotechnical laboratory for analysis, and the core holes were

backfilled and capped with asphalt concrete patch. No groundwater or saturated soil was encountered

within the explorations during our investigation.


The pavement cores generally encountered between 3¼ and 4½ inches of asphalt concrete. Cores C-1 to

C-3 were paved over fill soils that appeared to be derived from the native material. The subgrade soils

consisted predominately of silty sand with variable amounts of gravel. Refusal was encountered in each

of the core holes on cobbles. Core C-4 encountered an imported material that appeared to be an

aggregate base. The aggregate base was measured to be 12 inches in thickness before refusal was

encountered in the core hole. Measured core and aggregate base thicknesses (if present), as well as soil

classification of the subgrade are provided in Table 1.

Readings were taken in the core explorations using a dual-mass dynamic cone penetrometer in

accordance with ASTM D6951. The tip of the probe was placed at the top of the aggregate base or

subgrade layer and an 8-kilogram mass was dropped 30 times. The penetration was recorded for every

10 drops and is presented in Table 1. The dynamic cone penetration depth is used to identify areas of

loose or soft subgrade soils that may not support the construction equipment during rehabilitation.

Typically, a penetration greater than 7 inches for 10 drops will indicate a soft subgrade. The readings

taken during our field work indicated penetration between 1.0 and 2.1 inches for 10 drops, indicating soft

or loose conditions were not encountered at the locations tested.

TABLE 1 EXISTING PAVEMENT SECTIONS OF CORES

Laboratory testing of the subgrade soil included R-value and gradation. The laboratory test results are

presented on Figures A-1 and A-2. Testing of a combined sample of the subgrade yielded an R-value test

result of 72.

Two of the core samples were tested in our laboratory to measure the asphalt binder content and the

aggregate gradation of the extracted aggregate. The test results are presented on Figures A-3 and A-4.

Core

Measured

Asphalt

Concrete

Thickness (in)

Measured

Aggregate

Base

Thickness (in)

Subgrade USCS

Classification

Dual Mass Dynamic Cone Penetrometer

Readings (inches per 10 blows)

C-1 3 ¼ 0 SM 2.0 / 1.3 / 2.0

C-2 3 ¼ 0 SM 1.8 / 1.1 / 1.1

C-3 4 0 SM 2.1 / 1.4 / 1.0

C-4 4 ½ >12 Not Encountered 1.5 / 1.9 / 2.1


CONCLUSIONS AND RECOMMENDATIONS

It is our opinion that soil or geologic conditions were not encountered during the investigation that

would preclude rehabilitation of the roadway provided the recommendations presented herein are

followed and implemented during construction.

The field exploration indicates that the existing pavement structural sections have asphalt concrete

thicknesses between 3¼ and 4½ inches with aggregate base encountered beneath just one of the

pavements. Based on these measurements and the R-value of the subgrade, the existing pavement

sections for cores C-1 to C-3 would be expected to provide traffic indices on the order of 4.5 to 5.0,

which would not meet the current design TI. Adding additional layers to rehabilitate the existing

pavement and increase the TI is not practical due to the height of the overlay required. The roadways

should therefore be reconstructed with new structural sections to meet the design TI.

Based on the observed subgrade conditions, cement treatment of the subgrade soils or other recycling

methods such as full depth reclamation are not feasible due to the presence of cobbles in the site soils.

Based on this, rehabilitation techniques include reconstruction of the roadway with a new asphalt

concrete pavement over aggregate base or using a full depth asphalt concrete pavement over the

existing subgrade. The project civil engineer and Chaffey College should review the proposed

rehabilitation options and select the appropriate method. Geocon can provide additional

recommendations if alternate rehabilitation strategies are being considered.


New Pavements – Conventional Pavement

New pavements should be constructed to meet the current design traffic loads. We have included

pavement recommendations for TIs of 8 and 9 using the street designations and minimum pavement

sections from the City of Rancho Cucamonga Standard Drawings. Geocon should be contacted for

additional recommendations if other TIs apply.

The following preliminary pavement sections in Table 2 are recommended along College Drive where

new asphalt concrete pavements are planned. Pavement thicknesses were evaluated following procedures

outlined in the Caltrans Highway Design Manual. Laboratory test results of a combined sample indicated

a subgrade R-value of 72. We evaluated the pavement sections using an R-value of 50, the maximum

allowed in the Highway Design Manual. Final pavement sections should be evaluated based on R-value

testing of the soils encountered at the pavement subgrade during construction.

TABLE 2 RECOMMENDED CONVENTIONAL PAVEMENT DESIGN SECTIONS

Roadway

Classification

Traffic Index

(TI)

Subgrade

R-Value

Asphalt Concrete

(inches)

Aggregate Base

(inches)

Secondary 8 50 5.0 5.0

Major 9 50 5.5 6.5

The upper 12 inches of the subgrade soil should be compacted to a dry density of at least 95 percent of

the laboratory maximum dry density at slightly above optimum moisture content beneath pavement

sections.

Asphalt concrete should conform to Section 203-6 of the Greenbook. Class 2 aggregate base

materials should conform to Section 26-1.02A of the “Standard Specifications of the State of

California, Department of Transportation” (Caltrans). If used, Crushed Aggregate Base (CAB) should

conform to Sections 200-2.2 of the Greenbook. Base materials should be compacted to a dry density of

at least 95 percent of the laboratory maximum dry density at slightly above optimum moisture content.

Asphalt concrete should be compacted to a density of 95 percent of the laboratory Hveem density in

accordance with ASTM D 2726.


New Pavements – Full Depth Asphalt Concrete

As an alternative to conventional asphalt over aggregate base pavements, full depth asphalt concrete

pavements can be used to reduce the amount of excavation into the cobbly soils. Pavement thicknesses

were determined using the Caltrans Highway Design Manual. Roadway classifications and typical

traffic indices are provided. We have used an R-value of 50 for pavement design as that is the maximum

value allowed by Caltrans. The appropriate pavement section for the roadway based on the traffic index

should be verified by the civil engineer. Geocon should be contacted if alternative traffic indices are

appropriate.

The following preliminary pavement sections in Table 3 are recommended along College Drive for full

depth asphalt concrete. Pavement thicknesses were evaluated following procedures outlined in the

Caltrans Highway Design Manual using an R-value of 50. Final pavement sections should be evaluated

based on R-value testing of the soils encountered at the pavement subgrade during construction.

TABLE 3 RECOMMENDED FULL DEPTH ASPHALT PAVEMENT DESIGN SECTIONS

Roadway Classification

Traffic Index (TI)

Subgrade R-Value

Asphalt Concrete(inches)

Aggregate Base (inches)

Secondary 8 50 8.0 0

Major 9 50 9.5 0

Prior to placing asphaltic concrete, the upper 1 foot of subgrade surface soils should be moisture

conditioned to optimum moisture content and compacted to at least 95 percent of the laboratory

maximum dry density as evaluated by ASTM D1557.

Asphalt concrete materials should conform to Section 203-6 of the Greenbook. Asphalt concrete should

be compacted to a density of 95 percent of the laboratory Hveem density in accordance with

ASTM D2726.

General

The performance of pavements is highly dependent on providing positive surface drainage away from

the edge of the pavement. Ponding of water on or adjacent to the pavement surfaces will likely result

in pavement distress and subgrade failure. Drainage from landscaped areas should be directed to

controlled drainage structures. Landscape areas adjacent to the edge of pavements are not

recommended due to the potential for surface or irrigation water to infiltrate and cause distress.

Where such a condition cannot be avoided, consideration should be given to incorporating measures

that will significantly reduce the potential for subsurface water migration into the subgrade.


LIMITATIONS AND UNIFORMITY OF CONDITIONS

The recommendations of this letter pertain only to the portion of the site as indicated and are based

upon the assumption that the soil conditions do not deviate from those observed and discussed above.

If any variations or undesirable conditions are encountered during construction, or if the proposed

construction will differ from that anticipated herein. Geocon West, Inc. should be notified so that

additional supplemental recommendations can be given. The evaluation or identification of the

potential presence of hazardous or corrosive materials was not part of the scope of services provided

by Geocon West, Inc.

This report is issued with the understanding that it is the responsibility of the owner, or of his

representative, to ensure that the information and recommendations contained herein are brought to

the attention of the contractor, architect, and engineer for the project and the necessary steps are taken

to see that the contractor and subcontractors carry out such recommendations in the field.

The findings of this letter are valid as of the present date. However, changes in the conditions of a

property can occur with the passage of time, whether they are due to natural processes or the works of

man on this or adjacent properties. In addition, changes in applicable or appropriate standards may

occur, whether they result from legislation or the broadening of knowledge. Accordingly, the

recommendations in this letter may be invalidated wholly or partially by changes outside our control.

If you have any questions regarding this correspondence, or if we may be of further service, please

contact the undersigned at your convenience.

Very truly yours,

GEOCON WEST, INC.

Chet E. Robinson

GE 2890

Lisa A. Battiato

CEG 2316

CER:LAB:hd

Attachments: References

Figure 1, Vicinity Map

Figures 2, Coring Location Map

Figure A-1 through A-4, Laboratory Test Results

Distribution: Addressee (e-mail)

Geocon Project No. T2746-99-08 April 16, 2019

REFERENCES

1) ASTM International, 2005, Standard Test Method for Use of the Dynamic Cone

Penetrometer in Shallow Pavement Applications, ASTM D6951-03.

2) California Department of Transportation (Caltrans), 2015, Highway Design Manual,

dated July 1.

3) California Department of Transportation (Caltrans), 2010, Standard Specifications.

4) California Department of Transportation (Caltrans), 2008, Maintenance Technical Advisory

Guide, Volume I – Flexible Pavement Preservation, Second Edition, dated March 7.

5) Public Works Standards, Inc., 2015, “Greenbook” Standard Specifications for Public

Works Construction, Published by BNI Building News

6) Rancho Cucamonga, 2002, Standard Drawings, dated October 29.

Project

Site

SOURCE: Google Maps, 2018

COLLEGE DRIVE


CHAFFEY COLLEGE


APRIL, 2019 PROJECT NO. T2746-99-08 FIG. 1DF

VICINITY MAP

2000 ft

APRIL 2019 PROJECT NO. T2746-99-08 FIG. 2

COLLEGE DRIVEOMNITRANS TRANSIT CENTER TO PANTHER DRIVE

CHAFFEY COLLEGERANCHO CUCAMONGA, CALIFORNIA

CORING LOCATION MAP

DF

GEOCON LEGEND

Locations are approximate

C-1

……. CORE LOCATION

SCALE 1” = 80’

0 80 160

N

C-4

……. PROJECT EXTENTS

C-2

C-1

C-3

Pan

ther

Dri

ve

OmnitransTransit Center

LABORATORY TEST RESULTS

COLLEGE DRIVE OMNITRANS TRANSIT CENTER TO PANTHER DRIVE

CHAFFEY COLLEGE RANCHO CUCAMONGA, CALIFORNIA

APRIL, 2019 PROJECT NO. T2746-99-08 FIG A-1 DF

SUMMARY OF LABORATORY R-VALUE TEST RESULTS ASTM D2844

Sample No. Core No. R-Value

RV-1 Subgrade C-2 through C-4 combined 72

SAMPLE

ID

C-1

SAMPLE DESCRIPTION

SM - Silty SAND with Gravel

GRAIN SIZE DISTRIBUTION

COLLEGE DRIVEOMNITRANS TRANSIT CENTER TO PANTHER DRIVE

CHAFFEY COLLEGERANCHO CUCAMONGA, CALIFORNIA

APRIL, 2018 PROJECT NO. T2746-99-08 FIG A-2DF

3"

2"

1½

"

1 ¾"

½"

⅜"

#4

#10

#20

#40

#60

#80

#100

#200

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.1110100

PE

RC

EN

T P

AS

SIN

G

PARTICLE SIZE, mm


COLLEGE DRIVE


CHAFFEY COLLEGE



SAMPLE IDENTIFICATION

Sample No. C-1 Date Sampled: 04/05/2019

Sampled by: C. Robinson

Sample Location: College Drive

SUMMARY OF AGGREGATE GRADATION TEST RESULTS CT-202, ASTM C136

Sieve Size Test Results (% Passing)

1” 100.0

3/4” 100.0

1/2” 89.0

3/8” 76.9

1/4” 64.9

#4 56.6

#8 40.4

#10 37.8

#16 29.6

#30 21.5

#40 17.7

#50 14.3

#100 9.7

#200 6.6

SUMMARY OF ASPHALT BINDER CONTENT TEST RESULTS CT-382, ASTM D6307

Test Result (%) Based on Total Weight of Mixture

5.5


COLLEGE DRIVE


CHAFFEY COLLEGE



SAMPLE IDENTIFICATION

Sample No. C-3 Date Sampled: 04/05/2019

Sampled by: C. Robinson

Sample Location: College Drive

SUMMARY OF AGGREGATE GRADATION TEST RESULTS CT-202, ASTM C136

Sieve Size Test Results (% Passing)

1” 100.0

3/4” 85.7

1/2” 73.8

3/8” 88.0

1/4” 62.3

#4 54.7

#8 38.8

#10 36.5

#16 29.1

#30 21.7

#40 18.2

#50 15.0

#100 10.5

#200 7.2

SUMMARY OF ASPHALT BINDER CONTENT TEST RESULTS CT-382, ASTM D6307

Test Result (%) Based on Total Weight of Mixture

5.4