W912PL21B0005_Solicitation_Specifications_VolumeII.pdf

IFB No: W912PL21B0005

Lower Norco Bluffs Bluff Toe Protection

Santa Ana River - Prado Dam Riverside County, California

100% Total Small Business Set-Aside

Construction Solicitation and Specifications Volume II

7 May 2021 Solicitation

W912PL21B0005 Lower Norco Bluffs Toe Protection Riverside County, CA

7 May 2021 Solicitation

TABLE OF CONTENTS

Geotechnical Baseline Report: Lower Norco Bluffs

Geotechnical Data Report: Lower Norco Bluffs

Los Angeles District®

Geotechnical Branch

GEOTECHNICAL BASELINE REPORT

Prado Dam Flood Control Basin Norco, Riverside County, California

MARCH 2021

Geotechnical Baseline Report March 2021 i

Report Prepared By:

U.S. Army Corps of Engineers Engineering Division, Geotechnical Branch 915 Wilshire Blvd, Suite 930 Los Angeles, CA 90017

Michael Lau, P.E.

Embankment Engineer

Jeffery Geraci, P.G., C.E.G.

Engineering Geologist

With the Assistance of:

Jung Lee, P.E., Civil Engineer

Brian Hubel, P.E., G.E.

Geotechnical Engineer, SPK-DSPC

Report Reviewed by:

Douglas Dahncke, G.E., P.E.

Chief, Soils Design and Materials Section ii

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iii

TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 Location and Site Description

1.2 Project Description

1.3 Purpose of Geotechnical Baseline Report

1.4 Limitations of Geotechnical Baseline Report

2.0 FIELD AND LABORATORY INVESTIGATIONS

2.1.1 Previous Investigations

2.1.2 Current Investigation

2.1.3 Borrow Area Investigation

2.1.4 Groundwater Monitoring Wells

3.0 GEOLOGIC SETTING AND SUBSURFACE CONDITIONS

3.1 Local Site Geology

3.1.1 La Sierra Tonalite (Klst)

3.1.2 Quaternary Very Old Alluvium (Qvoa)

3.1.3 Quaternary Alluvium (Qal)

3.1.4 Talus (Qa)

3.1.5 Artificial Fill (af and Qaf)

3.2 Groundwater

4.0 GROUND CHARACTERIZATION

4.1 Foundation Conditions

4.2 Existing Bluffs

4.3 Soil Permeability

5.0 GEOTECHNICAL CONSIDERATIONS AND CONSTRAINTS

5.1 Borrow Materials

5.2 Abutments

5.3 Soft Subsurface

5.4 Old Diversion Channel

5.5 Soft Subgrade Soils

5.6 Bluff Stability

5.7 Groundwater Control

iv

5.8 Surfacewater Control

5.9 Launch Stone

6.0 REFERENCES .................................................................2Error! Bookmark not defined.

LIST OF FIGURES

Figure 1-1: Typical Cross Section

LIST OF TABLES

Table 2-1: Monitoring Well and Piezometer Summary

Table 3-1: Summary of Groundwater Conditions at the Time of Exploration

Table 3-2: Piezometer and Well Groundwater Fluctuation Summary

Table 4-1: Summary of Soil Classification of Foundation of New Embankment

Table 4-3: Foundation Permeability Summary

Table 5-1: Anticipated Subgrade Stabilization

LIST OF PLATES

Plate B-1: Regional Topographic Map and Vicinity Map

Plate B-2: Site Exploration Map

Plate B-3: Regional Geologic Map

Plate B-4: Site Geologic Map

Plate B-5 to 7: Geologic Cross Sections

Plate B-8: Geologic Profile X-X’

Plate B-9: 1960 Aerial Photography Proximity of Historic Drainage Channel

1.0 INTRODUCTION

1.1 Location and Site Description

The Lower Norco Bluffs project is located within the City of Norco, Riverside County, California. The project limits further bank erosion driven by impinging river flow to the bluffs on the east bank of the Santa Ana River approximately 5 miles north east of Prado Dam.

In the project limits the river meanders across a braided natural bottom channel. The City of Eastvale is on the right (north) bank. The City of Norco is on the left (south) bank, which consists of bluffs that rise upwards of 50 feet above the river channel. City of Norco residential development exists along the entirety of the bluff face. The river channel is currently used as a recreational horse and hiking trail area. The river channel was briefly developed in the 1950s with agriculture and equestrian facilities, but they were removed or destroyed by flood flows.

However, no previous developments have been constructed within the river channel through the project area. The Norco Naval Surface Warfare School, and later the California Institute of Prisons, operated a wastewater treatment plant that had an outfall into the river channel downstream of the project limits. A diversion channel was constructed between 1960 and 1962 parallel to the project alignment to serve the previous land use within the river channel and the wastewater treatment plant outfall. This diversion channel has been infilled with alluvial deposits from flood flows.

Existing bluffs are near vertical in areas of past bluff retreat (approximately station 54+00 to 64+00). The Norco Bluffs Feasibility Study estimated 1 to 3 feet of bluff retreat per year.

Outside of this over-steepened area, the bluff slopes vary in steepness between 1.1H:1V to 1.5H:1V.

1.2 Project Description

The Lower Norco Bluffs project will stabilize the Prado Dam Elevation 566 take line from further erosion caused by undercutting erosion by the Santa Ana River. The project consists of an earth fill placed against the existing bluffs, approximately 7,330 feet in length, revetted with riprap slope protection and a launch stone toe blanket. The project will tie into existing high ground at the upstream (Station 19+90) and downstream (Station 90+20) project extents, with an additional 300-foot-long access road.

The embankment fill will raise the grade between 12 and 25 feet above existing grade. The proposed embankment slope is 2H:1V and is revetted with riprap slope protection 42 inches thick, measured perpendicular to the slope face. Expected scour is between 5 and 18 feet below the existing thalweg (between 6 and 19 feet below existing grade at the project alignment). A launch stone toe is intended to provide some protection from scour. The launch stone toe is 9 feet high and varies in width, between 8 and 21 feet, depending on the expected scour depth along the project alignment.

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APPROX. EXISTING GRADE

EMBANKMENT FILL

EMBANKMENT FILL

VARIES

MAINTENANCE ROAD

VARIES

VARIES

0 10 20 30 40 50 60 70 80 90-10-20-30-40-50-60-70-80-90

9ft

TYPICAL CROSS SECTION

1-1

NORCO BLUFFS STABILIZATION PROJECT

RIVERSIDE COUNTY, CALIFORNIA

LOWER NORCO BLUFFS, NORCO

DATE: OCTOBER 2019

FILE NAME: NB_FIGURE1_1.DGNFILE NAME:

%STATUS%

Los Angeles District of Engineers

US Army Corps CHECKED BY: LAU

DRAWN BY:HERNANDEZ

DATE:

FIGURE

A

B

C

D

E

1 2 3 4 5 6 7

LAUNCH STONE TOE

RIP-RAP SLOPE PROTECTION

BEDDING MATERIAL

0 20 20 40FT

SCALE: 1''= 20'

1.3 Purpose of Geotechnical Baseline Report

The primary purpose of this Geotechnical Baseline Report (GBR) is to set a baseline for anticipated subsurface information to facilitate the bidding process in a such manner that all bidders can rely on a single contractual interpretation of geotechnical conditions for the proposed Lower Norco Bluffs project.

This report includes:

• Geologic and groundwater description of the site

• Geologic mapping, geologic and geotechnical profiles and cross sections

• Summary of anticipated subsurface conditions and ground characterization

• Summary of borrow site and material type

• Geotechnical considerations

• Construction considerations

1.4 Limitations of Geotechnical Baseline Report

This report presents the best judgement and interpretation of the subsurface conditions anticipated to be encountered during construction of the United States Army Corps of Engineers (USACE). The actual subsurface conditions encountered during the construction are expected to be more complex and vary from simplifications made for the design. The assumed design foundation conditions are based on engineering judgement to produce designs that are compatible with the complexities and variability of actual foundation conditions. In addition, the ground conditions will be influenced by construction activity and level of workmanship. The Contract Documents require bidders to consult with a geotechnical engineer familiar with all topics covered in this GBR. The Contractor’s geotechnical engineer should have similar experience and knowledge to interpret the presented data in this GBR to apprehend the complexity of the actual subsurface conditions.

2.0 FIELD AND LABORATORY INVESTIGATIONS

Subsurface investigations of foundation conditions for this project were conducted in several phases. More detailed discussion of the subsurface investigations including boring logs, field test results and laboratory test results are provided in the Geotechnical Data Report (GDR).

2.1.1 Previous Investigations

USACE conducted subsurface exploration in 1998 consisting of five test holes that were drilled using a hollow stem auger. Three test holes were drilled within the streambed to a minimum depth of 29.9 feet in May 1998, and two test holes were drilled at the top of the bluff to a maximum depth of 95 feet in July 1998.

Geomatrix Consultants, Inc., performed 21 additional borings in March 2000. Borings were drilled to determine subsurface conditions, depth to groundwater, and depth to impervious layer.

Two of these borings were performed at the top of bluff to a maximum depth of 98 feet below ground surface. The other 19 borings were within the streambed, drilled to a depth between 25 and 50 feet. The borings were completed with a 6-inch hollow stem auger. Samples were collected with both SPT and California Modified (Cal-Mod) samplers.

Data from the 1998 and 2000 investigations are presented in Appendix B of the GDR, including a plan showing the approximate boring locations and boring logs. Available laboratory data are incorporated into Appendix D of the GDR.

2.1.2 Current Investigation

Tetra Tech, Inc., performed supplemental subsurface investigations in 2019. A total of 30 cone penetration tests (CPTs), 10 rotary wash (RW) auger test holes, 9 test pits, and 2 bucket auger borings were conducted for this effort. A shear wave velocity survey was conducted to estimate the depth of bedrock. Additionally, four piezometers were installed with hand-drive methods by USACE personnel, described further in Section 2.1.4.

Rotary wash test holes were spaced along the project alignment, drilled to 50 feet depth and switched to coring down to 75 feet if bedrock was encountered. Four of the ten rotary wash borings were converted to coring. SPT and Cal-Mod samples were collected in the soil materials alternately at 5-foot intervals. SPT and Cal-Mod samples were used to confirm adopted shear strength parameters. Groundwater monitoring wells were developed at two of the rotary wash test hole locations, as described further in 2.1.4.

Test pits were conducted adjacent to rotary wash test hole locations to estimate the composition and volume of talus deposits at the base of the bluffs. Backhoe excavators reached as far up slope maximizing the equipment’s reach and test pits were excavated down to groundwater.

Bucket auger borings were conducted in October 2019 at two locations at the top of bluffs to depths of 76 and 91 feet below grade in an attempt to determine depth to bedrock and to map potential faulting and jointing within the bedrock that may contribute to large-scale slope instability. Both of the bucket auger borings were terminated in Pleistocene alluvium at depths below the projected toe of the bluff and did not encounter crystalline bedrock.

All explorations for the current investigation are shown on the Exploration Map (Plate B-2), and associated logs and test data are presented in the GDR.

2.1.3 Borrow Area Investigation

Prado Dam Borrow Area II has been identified as the borrow source for this project. This borrow is located south of the California Institute for Women in Corona, just west of Cucamonga Avenue and north of the recently disturbed borrow area used for Adobe Dike and LSAR R9P4.

The borrow area is marked by low hills, with elevations ranging between approximately 576 and 535 feet. The broad area designated in the 1988 Santa Ana River, Phase II General Design Memorandum (GDM) has been divided into sub-areas related to given projects.

2.1.4 Groundwater Monitoring Wells

Two groundwater monitoring wells were constructed as part of the 2019 investigation at Stations 52+00 and 85+00, MW-19-01 and MW-19-02 respectively.

Four Solinst Model 615 Drive-Point piezometers were installed in October 2020 by USACE staff. The wells were installed to depths of approximately 13 to 18 feet. The piezometer tips were adapted to segments of 1.25-inch galvanized pipe using threaded couplers. The larger diameter pipe above the tips was used in order to accommodate Solinst Levellogger (datalogging piezometers) for automatic data acquisition.

Three of the four piezometers were fitted with the datalogging piezometers, as were both monitoring wells at MW19-01 and MW19-02. A Solinst Barologger is installed at MW19-02 and is used for barometric correction at all the instrumented locations. Groundwater depths were baselined to manual readings that were obtained with an electronic well sounder.

Details are summarized in Table 2-1.

Table 2-1: Monitoring Well and Piezometer Summary

Well Number

Approx.

Station Top of Casing

Elevation (ft) Total

Depth (ft)

Elevation of Groundwater on

8 Dec 2020 Screened Interval

(ft)

MW-19-01 51+72 562.4 35 557.82 10-30

MW-19-02 85+45 570.8 34 565.96 10-30

P20-01 40+08 561.98 13.10 555.23 Open only at tip P20-02 34+53 561.29 13.95 554.04 Open only at tip P20-03 28+35 557.44 18.10 551.94 Open only at tip P20-04 27+05 556.39 13.2 551.29 Open only at tip

Note: Elevations are referenced to the NGVD 29 datum.

3.0 GEOLOGIC SETTING AND SUBSURFACE CONDITIONS

For anticipated geologic profiles and cross section along the project alignment, refer to attached Plates B-1 to B-9.

3.1 Local Site Geology

Mapped deposits beneath the Lower Norco Bluffs project site consist of Cretaceous La Sierra Tonalite (Klst); Quaternary Very Old Alluvium (Qvoa) consisting of Middle to Early Pleistocene moderately to well-consolidated highly dissected clay, silt, sand and gravel; Quaternary Alluvium (Qa) consisting of Holocene to Late Pleistocene unconsolidated to slightly consolidated, undissected to slightly dissected clay silt sand and gravel; Holocene Talus deposits (Qa), consisting of generally poorly consolidated avalanche debris near the toe of the bluff; and Artificial Fill (Qaf). Although not mapped in the immediate vicinity of the project, Late Cenozoic sedimentary rocks in the Norco Area (QTn) consisting of moderately indurated sandstone, conglomeratic sandstone and conglomerate occur in outcrop on the terrace south of the site and unconformably overlie the cretaceous intrusive rocks. Quaternary Old Fan Deposits (Qof) consisting of indurated sandy alluvial fan deposits occur southerly and easterly of the project site.

3.1.1 La Sierra Tonalite (Klst)

La Sierra Tonalite (Klst) consists of Cretaceous massive biotite tonalite. This crystalline intrusive unit is medium- to coarse-grained, structureless, locally with high-angle joints. Much of the tonalite is altered to secondary minerals, especially epidote and chlorite, with locally highly altered zones. Outcrops of La Sierra Tonalite are mapped throughout much of the Norco Area from north of Temescal Wash northward to the Santa Ana River and extending easterly to near the Riverside corporate boundary. Outcrops generally occur as inselbergs or monadnocks, surrounded by Tertiary and Quaternary sedimentary deposits. The unit is relatively fresh to deeply weathered, is locally mantled with up to about 10 feet of colluvial deposits (Qcol), and has greater resistance to erosion than the surrounding sedimentary deposits. Outcrops are mapped near the northernmost portion of the project site where the unit likely plays a key role in defining the course of the Santa Ana River.

3.1.2 Quaternary Very Old Alluvium (Qvoa)

Quaternary Very Old Alluvium (Qvoa) consists of early Pleistocene moderately to well-consolidated, reddish brown sand, gravel and silt. These valley deposits occur along stream valleys and alluvial flats of larger rivers. The unit is mapped to include coeval fan deposits and local colluvium. Occurrences of the various soil-type subunits are generally discontinuous throughout the deposit due to the variable geometry and temporal variability commonly associated with fluvial deposition and erosion. Very Old Alluvial Deposits are generally uplifted and locally overlie Cretaceous intrusive rocks and Tertiary marine sedimentary rocks. Qvoa is mapped locally along the bluff throughout the project site, is typically deeply weathered, and is capped with a well-developed pedogenic profile, with Bt horizons as much as 2 to 3 m thick. The unit typically yields to a talus slope at the toe of the bluff due to erosion by the Santa Ana River.

3.1.3 Quaternary Alluvium (Qal)

Quaternary Alluvium (Qal) consists of Holocene unconsolidated to slightly consolidated, undissected to slightly dissected clay, silt, sand, and gravel resulting from alluvial deposition of the Santa Ana River and its tributaries, and is generally mapped within the river channel.

Quaternary Alluvium is interpreted to include any of the Holocene alluvial deposits shown on the Regional Geologic Map as occurring within the Santa Ana River Channel. The unit unconformably overlies Qvoa, Klst, as well as any of the older sedimentary rock units shown on the Regional Geologic Map. Occurrences of the various soil-type subunits are generally discontinuous throughout the deposit due to the variable geometry and temporal variability commonly associated with fluvial deposition and erosion. Qal is generally less consolidated than Qvoa, with weak soil development. Quaternary alluvium is interpreted to interfinger with Talus Deposits (Qa) at the toe of the bluff.

3.1.4 Talus (Qa)

Talus (Qa) consists of Holocene, generally poorly consolidated sand and gravel avalanche deposits generally occurring at, or thickening toward, thee downslope portion of the bluff. These deposits are generally the product of episodic bluff collapse due to impinging river erosion and may contain localized high-angle landslide blocks. Talus deposits are interpreted to either interfinger with the channel alluvium or be locally truncated by the alluvium. Talus is interpreted to extend throughout the length of the project. The unit is observed to thin in plan-view toward the upstream end of the project where colluvial slope deposits are interpreted to thin atop the more resistant La Sierra Tonalite. Talus deposits are generally not mapped at the farthest upstream reach because of the economy of plan-view scale.

3.1.5 Artificial Fill (af and Qaf)

Various undocumented fills (Qaf) of limited thickness (less than 1–4 feet) are present along most of the alignment and are interpreted to be related to residential development along the top of the bluff. Those fills are generally interpreted from comparison with historical aerial photographs and large-diameter borings at the top of the bluff. Artificial fill may be encountered along portions of the bluff during site grading, especially in areas of significant canyon infill. The artificial fill deposit on the right bank of the Santa Ana River was mapped based on comparison with historical aerial photographs and represents southward encroachment into the channel.

Subsurface exploration was not conducted within the area of artificial fill on the right bank.

3.2 Groundwater

Groundwater levels were determined from subsurface explorations conducted during the current investigation including borings, monitoring wells, CPT soundings and piezometers. Groundwater levels estimated from CPT soundings ranged from 0 feet to 13 feet below grade at the time of exploration. Groundwater depths from the rotary wash borings and monitoring wells and piezometers ranged from 1.8 to 6 feet below grade. Groundwater was encountered in the large-diameter borings at 62 feet deep at BA19-01 and at 56 feet deep at BA19-02. Groundwater conditions are summarized in Table 3-1.

Table 3-1: Summary of Groundwater Conditions at the Time of Exploration

Station Nearest Test Locations

Estimated Depth to

Groundwater (ft, bgs)

Estimated Groundwater Elevation (ft)

+90+00 TT-19-09, CPT19-26 4.5 569

90+00 to 85+00

RW-19-09, CPT-19-25, CPT19-24,. RW19-08,

MW19-02 5 568

85+00 to 80+00

CPT19-23 3 566

80+00 to 75+00

RW-19-07, CPT-19-22, TT-19-08 4 564

75+00 to 70+00

RW19-06, CPT19-20 4 563

70+00 to 65+00

CPT19-18, CPT-19-19, TT-19-07 6 562

65+00 to 60+00

CPT-19-17, RW19-05, TT19-06, BA19-02 3 561

60+00 to 55+00

CPT-19-16, TT-19-05 2 560

55+00 to 50+00

CPT19-14, CPT-19-15, RW19-04, MW19-01 6 558

50+00 to 45+00

CPT-19-13, TT19-04 9 555

45+00 to 40+00

P20-01, CPT19-11, CPT-19-12 3 556

40+00 to 35+00

CPT-19-10 3 554

35+00 to 30+00

TT19-03, RW19-03, CPT19-08, BA19-01,

P20-02 3.5 553

30+00 to 25+00

CPT19-06, CPT-19-07, P20-03, P20-04 3 551

25+00 to 20+00

CPT-19-05, RW19-02, TT19-02 3 550

–20+00 RW19-01, CPT19-01, CPT19-02, CPT19-03,

TT19-01 5 545

Based on these data, groundwater generally flows to the southwest at a gradient of approximately

0.0013 feet/foot. For comparison, groundwater monitoring reports for a nearby site (14325 Chandler Street, approximately 1.2 miles northwest and on the right bank of the Santa Ana River) shows groundwater surface elevations ranging between 541.3 feet and 544.4 feet from 2010 to 2016 (Gaston 2016).

In general, groundwater flow is interpreted to extend from the bluffs into the river. Groundwater observed in the two bucket auger borings drilled in September 2019 and compared to CPT soundings within the river channel performed in March 2019, indicates a gradient between 19.7 (Station 30+90) and 0.35 (Station 62+00) percent.

Groundwater levels were measured along the river’s rise and fall after storm events. Several rain events and associated groundwater level changes have been documented. The full set of measurement data is included in the GDR and the range of measurements are summarized in Table 3-2. The contractor should expect groundwater may rise above the existing ground surface elevations within the stream channel during and after rainfall events. The groundwater levels are expected to be correlated with the river stage.

Table 3-2: Piezometer and Well Groundwater Fluctuation Summary.

Well/Piezometer

ID

Date Range of Data Range of GW fluctuation

(feet).

MW19-01 Sept 2019 to present ~ 5† MW19-02 Sept 2020 to present 2

P20-01 Oct 2020 to present 1 P20-02 Oct 2020 to present ½* P20-03 Oct 2020 to present 2 ¾† P20-04 Oct 2020 to present 2 ¾†

*Data is read manually and peak changes are likely missed.

†Measured pressures exceed the existing ground surface elevation

4.0 GROUND CHARACTERIZATION

Subsurface geologic profiles and cross sections were developed along the project alignment based on boring logs and understanding of site geology. The developed profiles and cross sections are highly subjective, as interpolation and extrapolation of data were required.

Discrepancies and inconsistencies are expected to occur during construction. Presented ground characterization is adequate for estimating quantities. Graphic representation of subsurface conditions including boring logs are included in the GDR.

4.1 Foundation Conditions

Soils that will be encountered at the foundation for the project include alluvium (Qal). talus (Qa), very old allvium (Qvoa), older alluvium (Qoa), and La Sierra Tonalite (Klst). These units are present adjacent to and within the bluff. The younger alluvial soils are generally poorly graded sand and silty sand. Throughout the project alignment, the foundation soils vary widely in texture, density, and stiffness due to the variable depositional history of the meandering channel.

A summary of the soil classification of the upper foundation is presented in Table 4-1.

Generally, the foundations soils are loose, poorly graded sand alluvial deposits within the top few feet, with more competent soils beneath. Medium to medium-dense sands and older alluvium were observed 15 feet below existing grade. Lenses and layers of various soil types were observed at various depths. Generally, borings did not encounter cobbles or gravelly soils;

however, these may be present but missed due to the wide-spacing subsurface investigations.

Table 4-1: Summary of Soil Classification of Foundation of New Embankment

Station Soil Classification Remarks

Estimated Depth to Bedrock (ft, bgs)

Estimated Bedrock

Elevation (ft)

+90+00 SM, SP loose (0 to 10 ft) to medium dense (<20 ft)

27.5 546.7

90+00 to 85+00

SM, SP medium dense (0 to 15 ft) 38.5 535.7

85+00 to 80+00

SP medium dense (0 to 15 ft) 32 538.9

80+00 to 75+00

SP-SM, SM very loose (0 to 5 ft) to medium dense (>15 ft)

26 544.6

75+00 to 70+00

SP, SP-SM Loose (0 to 15 ft) 35.5 to 46 521.6 to 535.4

70+00 to 65+00

SP, SM Loose (0 to 15 ft) 33 534.8

65+00 to 60+00

SP loose (0 to 10 ft) to medium dense (10 to 15 ft)

33 532.9

60+00 to 55+00

SP-SM, SP loose (0 to 10 ft) to medium dense (>15 ft)

26 546.5

Station Soil Classification Remarks

Estimated Depth to Bedrock (ft, bgs)

Estimated Bedrock

Elevation (ft)

55+00 to 50+00

SP loose (0 to 5 ft) to medium dense (5 to 10 ft)

27 542.4

50+00 to 45+00

SP loose (0 to 15 ft) to medium dense (>25 ft)

35 528.4

45+00 to 40+00

SP-SC, SC, SP,

SP-SM, SM

dense (0 to 20 ft) 43 to 43.5 593 to 600.4

40+00 to 35+00

SP medium dense (0 to 20 ft) 50 514.2

35+00 to 30+00

SP loose (0 to 10 ft) to medium dense (>15 ft)

30+00 to 25+00

SM loose (0 to 15 ft) to medium dense (>20 ft)

25+00 to 20+00

SM, SP, CL loose (0 to 10 ft) 27 527.7

–20+00 ML loose (0 to 5 ft) to medium dense (5 to 15 ft)

Note: Elevations are referenced to the NGVD 29 datum.

4.2 Existing Bluffs

Bluff materials consist primarily of older alluvial fan (Qvoa) fan sediments. Typically, these soils consist of a sandy clay (SC) surface layer underlain by silty sand (SM) and poorly graded sand (SP). Depth to igneous bedrock (Klst) within the bluff varies along the project alignment from surface exposures, from near-surface to upwards of 90 feet deep. An excavator was used to dig the test trench near Station 93+00, with excavation becoming progressively more difficult with depth, indicating a weathered profile at that location.

4.3 Soil Permeability

Estimated groundwater levels along the project alignment are presented in Section 3.2.

Slug tests were performed on the two groundwater monitoring wells at the installation in spring 2019 (see Table 4-3). Hydraulic conductivity (permeability) values from the slug tests ranged from 16 to 46 feet per day (fpd) and tested the upper 35 feet of foundation soils at well locations MW-19-01 and MW-19-02. The installed length of the well screens penetrated mostly uniform soil units and generally reflect the horizontal permeability of the tested soils.

The hydraulic conductivity values presented in Table 4-3 are considered typical for the area;

however, both higher and lower variations should be expected throughout the project.

Horizontal hydraulic conductivities measured over the excavation depths, faster than 0.1 cm/sec or slower than 1x10-4 cm/sec for more than 10% of the project alignment, shall be considered outside of the baseline interpretation.

Table 4-3: Foundation Permeability Summary

Well Approx.

Station

Approx.

Ground Elev. (ft)

Well Screen Depth

(ft)

Computed Effective Aquifer

Thickness (ft)

Geologic Map Units

Slug In K

(ft/day)

Slug Out K

(ft/day)

Average K

(ft/day) MW-19-01 52+00 562.4 10-30 35 Qal 16.3 18.6 17.4 MW-19-02 86+00 570.8 10-30 35 Qal 45.9 43 40.5

5.0 GEOTECHNICAL CONSIDERATIONS AND CONSTRAINTS

5.1 Borrow Materials

In general, the borrow area is comprised of coarse older alluvium, consisting of materials that classify between well-graded sands and clayey sands, and is overlain by about 1 to 4 feet of finer, younger alluvium and/or highly weathered older alluvium. The younger alluvium near the surface, which consists primarily of sandy clay, becomes increasingly thick at lower elevations.

This description of the borrow area stratigraphy is valid from a global standpoint, but it is not to say there are not variations. Isolated lenticular deposits such as silt, while not overwhelming, have been encountered during investigations, especially in the upper 6 to 8 feet. Care should be taken during excavation to ensure the specified gradations are obtained. Suitable materials for embankment fill are available in the borrow area; however, imported materials will be required for bedding and riprap.

All material types are authorized for use in embankment fill. A well-blended uniform fill is necessary for quality control. If the fill is inconsistent, much more testing effort will be required to ensure proper maximum densities are being used to assess if compaction is met. Excavation methods within the borrow area should be selected to maximize blending. All soils from required excavations and borrow areas should be stockpiled and blended as necessary prior to moisture-conditioning and placement on the dike embankment. Stockpiled material should be tested by both QC and QA and verified for conformance with the specification prior to placing on the dike embankment.

5.2 Abutments

Adequate benching and compaction is paramount at tie in locations. To prevent flanking of revetment and subsequently embankment fill, additional compaction effort using portable equipment or compaction wheel will be required to ensure tie in locations have satisfactory foundation conditions prior to fill placement. No geotechnical exploration was conducted at the tie-in locations. However, excavation is anticipated to become progressively difficult with depth at the north abutment indicating a weathered bedrock profile. Estimated removal of approximately 350 cubic yards of loose weathered rock in the vicinity of the north abutment should be anticipated. No blasting or ripping of bedrock will be required for the project.

5.3 Soft Subsurface

With relatively shallow groundwater near the vicinity of the abutments and between Stations 55+00 to 60+00, meeting adequate compaction requirements for subsurface preparation is anticipated to be difficult. To prevent the subsurface soil from pumping, additional work for subsurface stabilization is anticipated.

In the areas where additional subsurface stabilization is provided, meeting subgrade compaction requirements at the foundation excavation elevation will not be required. The fill placed above the stabilized subgrade will be required to meet the specifications. The limit of subsurface stabilization will be within the footprint of embankment fill and will not go beyond the stone protection. Refer to Table 5-1 for anticipated area of subgrade stabilization.

5.4 Old Diversion Channel

A diversion channel was excavated approximately 200 feet from the bluffs, sometime between 1960 and 1962 based on aerial photography, to provide irrigation to agriculture plots within the river channel and for the sewer treatment plant associated with the Norco Naval Surface Warfare Center. The diversion channel was washed out sometime between 1965 and 1967 based on aerial photography. It is likely that the diversion channel was infilled with loose silt deposits, which may account for the stuck vehicle described in the Memorandum dated December 16, 2019 (provided in Appendix A of the GDR). Location of the diversion channel with respect to the Temporary Construction Easement (TCE) and project alignment is provided on Plate B-4, and an overlay of the project control line on the January 1962 aerial photograph is provided on Plate B- 9.

The diversion channel is located within the project TCE between Stations 19+00 to 39+00, 45+00 to 60+00, 69+00 to the project end (beyond Station 90+00). The construction access road alignment crosses the diversion channel alignment multiple times as it approaches the downstream project extent. There may be difficulty for construction vehicle access when driving within the former diversion channel alignment.

The diversion channel is outside the embankment footprint except for between Stations 18+00 to 31+00, 53+00 to 54+00 and 88+00 to 90+00. There may be difficulty operating standard equipment in these areas. Due to the expected loose soils, wide track vehicles and subsurface stabilization may be required in these areas.

5.5 Soft Subgrade Soils

Table 5-1 provides anticipated areas in need of subgrade stabilization within the embankment footprint along the project stationing. However, because of the limited number of explorations and potential additional areas of soft subgrade, estimated area in need of subsurface stabilization is assumed to be approximately 85 percent of the length of the project alignment from toe of the embankment fill to the toe of the existing bluff. Additional stabilization measures and specialized equipment are anticipated to be needed for haul roads located outside of the embankment footprint, especially in the old diversion channel alignment.

Table 5-1: Anticipated Subgrade Stabilization

Station Soil Classification Remarks Subgrade

Stabilization

+90+00 SM, SP loose (0 to 10 ft) to medium dense (<20 ft)

N/A

90+00 to 85+00

SM, SP medium dense (0 to 15 ft) N/A

85+00 to 80+00

SP medium dense (0 to 15 ft) N/A

Station Soil Classification Remarks Subgrade

Stabilization 80+00 to 75+00

SP-SM, SM very loose (0 to 5 ft) to medium dense (>15 ft)

Stabilization Recommended

75+00 to 70+00

SP, SP-SM Loose (0 to 15 ft) Stabilization Recommended

70+00 to 65+00

SP, SM Loose (0 to 15 ft) Stabilization Recommended

65+00 to 60+00

SP loose (0 to 10 ft) to medium dense (10 to 15 ft)

Stabilization Recommended

60+00 to 55+00

SP-SM, SP loose (0 to 10 ft) to medium dense (>15 ft)

Stabilization Recommended

55+00 to 50+00

SP loose (0 to 5 ft) to medium dense (5 to 10 ft)

Stabilization Recommended

50+00 to 45+00

SP loose (0 to 15 ft) to medium dense (>25 ft)

Stabilization Recommended

45+00 to 40+00

SP-SC, SC, SP,

SP-SM, SM

dense (0 to 20 ft) N/A

40+00 to 35+00

SP medium dense (0 to 20 ft) N/A

35+00 to 30+00

SP loose (0 to 10 ft) to medium dense (>15 ft)

Stabilization Recommended

30+00 to 25+00

SM loose (0 to 15 ft) to medium dense (>20 ft)

Stabilization Recommended

25+00 to 20+00

SM, SP, CL loose (0 to 10 ft) Stabilization Recommended

–20+00 ML loose (0 to 5 ft) to medium dense (5 to 15 ft)

Stabilization Recommended

5.6 Bluff Stability

No bluff stabilization is occurring as part of this project. No buttress fills or slope gradient changes are being made to stabilize the current bluff geometry. The bluff as is, is currently near stability equilibrium. A vegetated swath is being included between the toe of the bluff and the maintenance road and swale drain. This area will need to be cleared of debris following surficial failures as a part of ongoing operation and maintenance responsibility.

5.7 Groundwater Control

Based on the proposed excavation limits, it is highly likely that the shallow groundwater will be encountered at Stations 90+00 to 55+00 and Stations 45+00 to 20+00 along the project alignment during the dry seasons. During the wet season, groundwater may be encountered in any project excavation. Anticipate groundwater control using trench drains and sump pumps at the excavation toe with addition of subsurface stabilization described in the previous sections.

5.8 Surfacewater Control

The low-flow channel of the river has and will continue to experience migration. Within the last several years, near project station 31+00, the active channel has meandered to encroach on the project area. The contractor shall anticipate the need for approximately 1,000 feet of sheet pile or other or similar cofferdam in the vicinity, to keep surface water out of the project construction site. In other areas of the project, temporary earth fills are anticipated to be adequate for surface water control. Project specifications provide required flow conditions the contractor shall anticipate for surface water control.

5.9 Launch Stone

To minimize the potential of the formation of voids occurring in the embankment and foundation due to internal erosion, the voids in the launch stone toe must be adequately filled during construction. The launch stone toe must be constructed in lifts or some method that allows for filling of voids between the rock particles, while still allowing for the interlocking of the stone.

Excavated material for the launch stone toe is predominately composed of coarse grain material and is the preferential source for void in fill. The sand from the excavation of the launch stone toe should be washed or jetted into voids for each lift of stone placed.

With potential soft subsurface conditions, some subsidence could occur during the placement of launch stone. In case of subsidence of launch stones during placement, meeting the required height of launch stone given in the plans will be based on the volume of rock placed on the slope.

6.0 REFERENCES

GeoSoils (2007). Update Geotechnical Evaluation and Grading Plan Review (60-Scale), Tract 31643-2 (Park/School Site), Eastvale Area, Riverside County, California, for Standard Pacific Corporation, W.O. 5122.4-A.SC, dated September 6, 2007.

Names Committee of the U.S. Geological Survey, USGS (2010). Divisions of Geologic Time, Major Chronostratigraphic and Geochronologic Units, U.S. Geological Survey Fact Sheet 2010- 3059, July 2010, 2 p.

United States Army Corps of Engineers, Los Angeles District, USACE (1996). Norco Bluffs, Riverside County, California, Feasibility Study, Geotechnical Appendix, dated 8 August 1996.

United States Army Corps of Engineers, Los Angeles District, USACE (1988). Santa Ana River

– Design Memorandum No. 1, Phase II General Design Memorandum on the Santa Ana River Mainstem including Santiago Creek, Volume 2 Prado Dam, dated August 1988.

United States Army Corps of Engineers, Los Angeles District, USACE (1973). Design Memorandum No. 2, General Design For Flood Control and Recreation, Cucamonga Creek, San Bernardino and Riverside Counties, California, dated June 1973.

United States Geological Survey, USGS (2018). Unified Hazard Tool, https://earthquake.usgs.gov/hazards/interactive/.

Yerkes, R.F., McCulloh, T.H., Schoellhamer, J.E., and Vedder, J.G. (1965). Geology of the Eastern Los Angeles Basin, Southern California, in Geology of the Los Angeles Basin California

– an Introduction, Geological Survey Professional Paper 420-A, United States Geological Survey (USGS), 57 p. and 4 plates.

Pl ot

D at e:

, P lo tte d by : l

1e dg jp g, F ile

N am e:

L

N B_

R

EG

IO

N

AL

T

O

PO

G R

AP

H

IC

M

AP

.C

D R

U

SG

S

To po gr ap hi c

M ap

(2

5)

Approximate Scale in Feet

00 4000' 8000'

SANTA ANA RIVER MAINSTEM, CALIFORNIA

LOWER NORCO BLUFFS

NORCO, CALIFORNIA

REGIONAL TOPOGRAPHIC MAP

US Army Corps of Engineers Los Angeles District

CKD BY:

DWN BY: JPG

DATE: 2020

PLATE

Reference: Portions of Prado Dam and Corona North, California USGS Topographic Quadrangles, 2015

North American Datum of 1983 (NAD83) World Geodetic System of 1984 (WSGS84). Projection and 1,000-meter grid: Universal Tranverse Mercator, Zone 11S 10,000-foot tick: California Coordinate System of 1983 (Zones 5 and 6) North American Vertical Datum of 1988 (NAVD88)

ALL LOCATIONS ARE APPROXIMATE

PRADO

DAM

SANTA ANA RIVER

PROJECT AREA

Lower Norco Bluffs

BORROW SITE

Ref: Sheet G-004

LOWER NORCO BLUFFS, NORCO

RIVERSIDE COUNTY, CALIFORNIA

PLAN OF EXPLORATION

JPG

JPG

January 2021 B-2 PLATEUS Army Corps of Engineers Los Angeles District

CKD BY:

DWN BY:

DATE:

BA-19-02

BA-19-01

P-20-01

P-20-02

P-20-03

P-20-04

TT-19-01

TT-19-02

RW-19-02

RW-19-01

CPT-19-02

CPT-19-03

CPT-19-05

Location of rotary wash boring

Location of cone penetrometer (CPT) sounding

Location of test trench

Location of piezometer or monitoring well

BA-19-02 Location of large-diameter bucket-auger boring

SL-45 Location of shear wave velocity profile

Explanation of Symbols

APPROX. SCALE 1:3,600

APPROXIMATE MEAN

DECLINATION, 2019

M A

G N

E

TI

C N

O R

TH

11 / °1 2

TR

U

E N

O R

TH

0 300 ft

0 1 in

Qal

Qal

Qal

Former Diversion Canal from 1962 Aerial Photograph (see Plate B-9)

Qaf

(Klst)

Qaf

Qaf

Qaf

Qaf

Qaf

Qaf Qaf

Qaf

Qvoa

Qvoa

Qvoa

Qvoa

Qvoa

Klst

KlstQa

Qa

Qa

Qa

(outcrops)

BA-19-02

BA-19-01

P-20-01

P-20-02

P-20-03

P-20-04

TT-19-01

TT-19-02

RW-19-02

RW-19-01

CPT-19-02

CPT-19-03

CPT-19-05

A

A’

B

B’

C

C’

Project Control Line and Stationing

APPROX. SCALE 1:3,600

APPROXIMATE MEAN

DECLINATION, 2019

M A

G N

E

TI

C N

O R

TH

11 / °1 2

TR

U

E N

O R

TH

0 300 ft

0 1 in

Description of Map Units

Qal ALLUVIUM (Holocene)- Young surface deposits resulting from alluvial deposition of the Santa Ana River, and generally occurring within the river channel. May include minor earth fill and talus deposits.

Qaf

Qa

Qvoa

Klst

Description of Map Symbols

Lithologic contact, approximately located

ARTIFICIAL FILL (recent): Clayey sand, fine- to medium-grained, generally undocumented. Mapped based on aerial photographic evidence and on occurrence at local explorations.

TALUS (Holocene): Generally poorly-consolodated sand and gravel avalanche deposits generally occurring at, or thickening toward the downslope portion of the bluff, and generally resulting from episodic bluff collapse due to impinging river erosion.

VERY OLD ALLUVIAL DEPOSITS (early Pleistocene): Sand, gravel and silt; reddish-brown, well-indurated. Mapped by Morton and Gray (2002) as early Pleistocene channel deposits, and incorporated herein to include coevial proximal fan deposits and colluvium (Qcol). The surface of these deposits is deeply-weathered and capped with a well-developed pedogenic profile with Bt horizons as much as 10 feet thick. The unit generally yields to a talus slope at the toe of the bluff due to river erosion. Includes minor earth fill associated with residential development and minor Holocene alluvium (Qal) occupying tributary drainages.

LA SIERRA TONALITE (Cretaceous): Massive biotite tonalite. Medium- to coarse-grained;

structureless, locally with high-angle joints. Much of the tonalite is altered to secondary minerals, especially epidote and chlorite; with localized highly-altered zones. Mapped based on observed outcrops and historical subsurface data; and interpreted in cross-sections based on increase in S-Wave velocity contrast. Includes areas interpreted to be covered with up to approximately 10 feet of colluvium (Qcol) where surface outcrops are not apparent, as well as areas interpreted to contain minor earth fill associated with residential development.

Location of rotary wash boring

Location of cone penetrometer (CPT) sounding

Location of test trench

Location of piezometer or monitoring well

BA-19-02 Location of large-diameter bucket-auger boring

C

C’ Cross-section line

Lithologic contact, concealed or inferred

Surface outcrop

75 Strike and dip of joints in La Sierra Tonalite

X

X’ Profile line, offset 50 feet right of Project Control Line

PLATEUS Army Corps of Engineers Los Angeles District

CKD BY:

DWN BY:

DATE:

Lower Norco Bluffs Norco, CA

Geologic Map

January 2021

JPG B-4

Notes: 1) Stationing and control line are based on working plans developed on March 4, 2020.

Klst interpreted as concealed \ beneath shallow undocumented fill

65 75 70 60

X’

X

Approximate location of historical diversion canal (Plates B-4 and B-9)

Note: The color scale for the projected V tomographic profile is presented in the report by Geovision in Appendix A of the GDR, and is independent of lithologic color scheme on the Geologic Map. s

Existing ground surface

Note: The color scale for the projected V tomographic profile is presented in the report by Geovision in Appendix A of the GDR, and is independent of lithologic color scheme on the Geologic Map. s

Approximate location of historical diversion canal (Plates B-4 and B-9)

Note: The color scale for the projected V tomographic profile is presented in the report by Geovision in Appendix A of the GDR, and is independent of lithologic color scheme on the Geologic Map. s

PLATEUS Army Corps of Engineers Los Angeles District

CKD BY:

DWN BY:

DATE:

Lower Norco Bluffs Norco, CA

Geologic Profile X-X’

January 2021

JPG B-8

BA

-0 ft R t

C

PT

-1 9-

R W

-0

7/ C

-0

C

PT

-1 9-

R W

-0

6/ C

-0

C19-09 (cored)

RW19-09 (rotary)

C19-08 (cored)

RW19-08 (rotary)

C

PT

-1 9-

C19-07 (cored)

RW19-07 (rotary)

R W

-0

9/ C

-0

C

PT

-1 9-

C

PT

-1 9-

C

PT

-1 9-

C19-06 (cored)

RW19-06 (rotary)

C

PT

-1 9-

C

PT

-1 9-

R W

-0

5/ C

-0

C

PT

-1 9-

C19-05 (cored)

RW19-05 (rotary)

C ro ss -s ec tio n B-

B’

C

PT

-1 9-

C

PT

-1 9-

R W

-0

4/ M

W

-0

C

PT

-1 9-

RW19-04 (Klst) R

W

-0 8/

C

-0

M W

-0

SL-33

SL-33

SL-32

SL-31

SL-30

SL-29

SL-29

SL-28

SL-27

SL-27

SL-26

SL-25

SL-24

SL-23

SL-22

SL-21

Klst

Qa

Qal

Klst

Qa

QvoaKlst Qvoa

Qvoa

Qa

QvoaKlst

Qa

Klst

Qa Klst

Klst

Klst

Klst

QalQvoa Qa

Qvoa

Klst Klst

Qa

Qa

Qvoa

Klst Klst

Klst

QaQvoa Qa

Qvoa Qa Qal Qvoa

Qvoa

Ground surface at Profile X-X’

Ground surface at Control Line

(~50 ft right of Control Line)

V Tomographic Profiles and Sequence Numbers s

(seismic lines acquired in vicinity of project control line)

CPT (derived) SPT N60 Plots (indicates relative penetration resistance in vicinity of control line)

Test Holes in vicinity of Control Line (indicating rotary wash and cored segments)

Large-Diamater (bucket auger) Boring (drilled at top of bluff)

Lithologic contacts at Profile X-X’ (dashed where approximately located)

Lithologic Units at Profile X-X’ (as described on the accompanying Geologic map)

Notes: 1) Geologic Profile X-X’ is intended to primarily depict the lithology along that profile, located 50 feet right of the Project Control Line. The location is shown in plan-view on the accompanying Geologic Map. Most of the explorations shown on this profile were performed in the vicinity of the project control line, and have been included on this profile to provide a sense of perspective. The large-diameter boring at BA19-02 was drilled at the top of the bluff, 223 feet right of the control line (173 feet right of Section X-X’). Lithology and lithologic contacts shown on this profile are representative of the approximate conditions within a vertical plane along Section X-X’.

2) Profile view is looking toward bluff from Santa Ana River Channel.

3) Lithology colors correspond to the Description of Map Units shown on Plate B-4. The color scale for the projected V tomographic profiles is presented in the report by Geovision in Appendix A of the GDR, ands are independent of lithologic color scheme.

Scale 1:480 (1in = 40 ft)

VS=HS

X

X’

Pr ofi le c on tin ue d be lo w Pr ofi le c on tin ue d be lo w

Pr ofi le c on tin ue d be lo w

Be gi n Pr ofi le

En d of P ro fil e

G

F

E

D

C

B

A

1 2 f.lllE:IIU!l\lBrawings\Models\Geotechn ical\FROM DESIGN\PLA TEaerial.dgn

11 :52:40 PM 4/13/2020 PD: AEC_pdf.pltcfg DS: AEC_Screen.dscript

3 4 5 6 7 8

- - m

ORANGE COUNTY, CALIFORNIA

LOWER NORCO BLUFFS

1962 Aerial Photography Proximity of Historical Diversion Channel

US Army Corps of Engineers ®

Los Angeles District

CHECKED BY: LAU

DRAWN BY:HERNANDEZ

DATE:

PLATE

B-9 rn N rn r m

Note: Aerial photograph reference: Flight C-24244, frame 3-541, dated 30 January 1962, scale 1:24,000; by Fairchild Aerial Surveys. Copyright UC Regents.

January 2021

Los Angeles District®

Geotechnical Branch

GEOTECHNICAL DATA REPORT

Prado Dam Flood Control Basin Norco, Riverside County, California

February 2021

Geotechnical Data Report February 2021 i

Report Prepared By:

U.S. Army Corps of Engineers Engineering Division, Geotechnical Branch 915 Wilshire Blvd, Suite 930 Los Angeles, CA 90017

Michael Lau, P.E.

Embankment Engineer

Jeffery Geraci, P.G., C.E.G.

Engineering Geologist

With the Assistance of:

James Lee, P.E.

Soils Design and Materials Section

Brian Hubel, P.E., G.E.

Geotechnical Engineer, SPK-DSPC

Report Reviewed by:

Douglas Dahncke, G.E., P.E.

Chief, Soils Design and Materials Section ii

(THIS PAGE LEFT INTENTIONALLY BLANK)

iii

TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 Limitations

1.2 Location and Site Description

1.3 Project Description

2.0 FIELD AND LABORATORY INVESTIGATIONS

2.1 Subsurface Investigations

2.1.1 1998 Investigation

2.1.2 2000 Investigation

2.1.3 2019 Investigation

2.1.4 Borrow Area Investigation

2.1.5 Groundwater Monitoring Wells

2.2 In-Situ Geotechnical Testing

2.2.1 Slug Tests

2.2.2 Shear Wave Velocity

2.3 Geotechnical Laboratory Testing

3.0 TOPOGRAPHIC AND SUBSURFACE CONDITIONS

3.1 Topography and Drainage

3.2 Regional Geology

3.3 Regional Faulting and Seismicity

3.4 Local Site Geology

3.4.1 La Sierra Tonalite (Klst)

3.4.2 Quaternary Very Old Alluvium (Qvoa)

3.4.3 Quaternary Alluvium (Qal)

3.4.4 Talus (Qa)

3.4.5 Artificial Fill (af and Caf)

3.5 Groundwater

3.6 Foundation Conditions

4.0 REFERENCES

iv

LIST OF FIGURES

Figure 3-1: Earthquake Faults in Southern California (CDC, 2018)

Figure 3-2: Well Measurements, 30 August 2019 to 14 January 2021

LIST OF TABLES

Table 2-1: 1998 Investigation Boring Summary

Table 2-2: 2000 Investigation Boring Summary

Table 2-3: 2019 CPT Sounding Summary

Table 2-4: 2019 Rotary Wash Boring and Coring Summary

Table 2-5: 2019 Test Pit Summary

Table 2-6: 2019 Bucket Auger Boring Summary

Table 2-7: Monitoring Well Summary

Table 2-8: Rotary Wash Samples Index Property Test Summary

Table 2-9: Test Trench Samples Index Property Test Summary

Table 2-10: Direct Shear Test Summary

APPENDICES

Appendix A – 2019 Subsurface Investigation Logs for Project Site

Appendix B – Previous Investigations Logs

Appendix C – Groundwater Data Test Results

Appendix D – Geotechnical Laboratory Test Results for Foundation Soils

Appendix E – Geotechnical Laboratory Test Results for Borrow Materials v

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1.0 INTRODUCTION

This Geotechnical Data Report (GDR) presents the collected data from current and previous geologic and geotechnical investigations completed for the Lower Norco Bluffs project located within the City of Norco, Riverside County, California. Geotechnical investigations were performed by the United States Army Corps of Engineers (USACE), Geomatrix Consultants, Inc., Tetra Tech, and others that are pertinent to the currently proposed Lower Norco Bluffs project. The geologic and geotechnical investigations for the subject project consisted of exploratory borings, test trenches, groundwater monitoring wells, and cone penetration tests (CPTs), as well as laboratory testing on selected samples.

1.1 Limitations

The information presented in this report is intended to be factual geotechnical and geologic data.

This data is from limited surface and subsurface investigations, limited lab testing, and soil and rock identification and classification that, in part, rely on professional judgement of USACE and consultant engineers and geologists. The data documented in the GDR represents conditions encountered during the time of the exploration. The actual field conditions may differ from the data presented due to limitations of the investigation methods, laboratory testing and other uncertainties. Field conditions may change over time due to seasonal effects, meandering of the Santa Ana River low-flow channel, and changes in site conditions from construction activities.

1.2…