935030-20230413 Addendum 3.pdf

ADDENDUM NO. 3

TO THE CONTRACT DOCUMENTS AND SPECIFICATIONS FOR

DELTA PONDS TRAIL EXTENSION

April 13, 2023 PROJECT #935030 BID NUMBER 7

TO ALL PLANHOLDERS:

The following changes shall amend and supplement the project bidding documents only to the extent specifically shown and noted. All other conditions shall remain the same.

Bidders shall incorporate the effects of these changes in the appropriate bid items included in this addendum and the total of these bid items then add in the appropriate place on the bid form.

(ADD) Geotechnical Report

CHANGES TO CALL FOR BIDS AND PROPOSAL:

BID CLOSING DATE:

(DELETE) Thursday, April 13, 2023 – 2:00 PM

(ADD) Tuesday, April 18, 2023 – 2:30 PM

CHANGES TO SPECIAL PROVISIONS:

(REPLACE) 00150.15 Construction Stakes, Lines, and Grades:

(a) General - The Contractor shall perform no Work until the Engineer establishes field controls. Work performed without field controls will be subject to removal at the Contractor's expense.

(b) Agency Responsibilities - The Engineer will:

• Lay out and set construction stakes and marks to establish the lines, grades for trail work;

• Provide one set of construction stakes for line and grade for each additional phase of the Work as follows:

1. Right of way & Easement lines - Location.

2. Retaining walls – Locations and retaining wall height.

3. Crosswalk Corner – Finish grade at grade breaks.

4. Pipes – Invert elevation at centerline of the pipe.

5. Trail Centerline – Location and finish grade trail centerline.

6. Inlet – Location and one invert elevation.

7. Bridge Substructure – End Bents and wingwall locations.

Addendum #3 – Job #935030 Page 2

• The Agency will replace survey monuments disturbed during construction that have not been noted in the Plans to be protected.

• Calculate and provide finish deck grades; and Deduct from payments due the Contractor all costs incurred to replace stakes and marks negligently or intentionally damaged, removed, or destroyed by the Contractor.

(c) Contractor Responsibilities - The Contractor shall:

• Inform the Engineer of staking requirements at least 5 Calendar Days before the staking needs to begin;

• Coordinate construction to provide sufficient area for the Engineer to perform surveying work efficiently and safely;

• Accurately measure detailed dimensions, elevations, and Slopes from the Engineer's stakes and marks;

• Perform the Work in such a manner as to preserve stakes and marks; and

• Set any reference lines for automatic control from the control stakes provided by the Engineer.

• Inform the Engineer of any property corners monuments and/or survey markers that are not shown on the plans and are found during construction activities prior to disturbing the monuments. Allow the Agency 2 Work Days for referencing all found markers before they are removed. Monuments that are noted on the plans to be protected and are disturbed by the Contractor's activities shall be replaced by the Contractor’s surveyor at the Contractor's expense.

CHANGES TO PLANS:

(REPLACE) Sheet S2.0 8.5 x 14 sheet from Addendum 2 with Sheet S2.0 11 x 17 sheet

(REPLACE) Sheets EC1.0, EC1.1, EC3.0, EC4.0, EC5.0, and EC5.1 with

Sheets EC1.0, EC1.1, EC3.0, EC4.0, EC5.0, and EC5.1 - Addendum #3

If you have questions about this addendum or the project, please contact Rachael Vaicunas at 541-729-2963 or rvaicunas@eugene-or.gov.

All bidders shall acknowledge the receipt of and acceptance of this Addendum No. 3 by signing and submitting the signed Addendum with the bid. Bids submitted without this Addendum, or with the Addendum not signed, may be considered non-responsive according to 00120.70.

Jenifer Willer, P.E.

City Engineer

Receipt acknowledged and conditions agreed this day of , 2023.

Bidder: _____________________________

By: _____________________________

RCV

RCV

Jenifer Willer (Apr 13, 2023 09:22 PDT) https://cityofeugene.na2.documents.adobe.com/verifier?tx=CBJCHBCAABAAmITRJY4nligmOxGZoCvqO0n7CpgCaZMD https://cityofeugene.na2.documents.adobe.com/verifier?tx=CBJCHBCAABAAmITRJY4nligmOxGZoCvqO0n7CpgCaZMD

October 18, 2019 6247 GEOTECHNICAL RPT

KPFF, Inc.

800 Willamette Street, Suite 400 Eugene, OR 97401

Attention: Pete Miller, PE

SUBJECT: Geotechnical Investigation

Delta Ponds Trail Extension Eugene, Oregon

As requested, GRI completed a geotechnical investigation for the proposed Delta Ponds Trail extension in Eugene, Oregon. The general location of the project is shown on the Vicinity Map, Figure 1. The purpose of our investigation was to evaluate subsurface conditions at the site and develop conclusions and recommendations for design and construction of a new pedestrian bridge over Debrick Slough, which will be part of a planned trail extension around Delta Ponds in Eugene, Oregon. The investigation included a review of existing studies and available geologic and geotechnical information for the site, a site reconnaissance, subsurface explorations, laboratory testing, and engineering analyses. This report describes the work accomplished and provides our conclusions and recommendations for use in design and construction of the project.

The improvements are anticipated to be designed in accordance with these current American Association of State Highway and Transportation Officials (AASHTO) design guidelines:

2017 AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications

(AASHTO BDS)

2011 AASHTO Guide Specifications for LRFD Seismic Bridge Design (AASHTO SBD)

2009 AASHTO LRFD Guide Specifications for the Design of Pedestrian Bridges

2019 Oregon Department of Transportation Bridge Design Manual

All elevations in this report are based on the North American Vertical Datum of 1988 (NAVD 88).

PROJECT DESCRIPTION

Delta Ponds is a City of Eugene-owned property comprising approximately 150 acres of wetlands, riparian areas, ponds, sloughs, and channels. The enhancement of Delta Ponds has been an ongoing project over the last decade and includes existing improvements such as a gravel-surfaced trail around the majority of the perimeter of Delta Ponds and Debrick Slough. The project will complete the pedestrian loop around Delta Ponds with a new trail segment at the northeast corner of the current trail system.

The new improvements will include approximately 1,250 ft of new gravel-surfaced trail, several hundred feet of wooden boardwalk, and a pedestrian bridge over Debrick Slough. Based on our review of the preliminary plans for the project, we understand construction of the new trail segment will require cuts and fills of less than about 4 ft and supported by gravity block retaining walls where required.

Based on preliminary information provided by you, we understand the planned single-span, pre-engineered bridge will be approximately 100 ft long and 8 ft wide. The total unfactored load at each abutment is estimated at 50 kips. Existing pedestrian bridges on the trail are supported on spread footings and we anticipate spread footings will be appropriate for use at this location as well. Based on our review of the bridge alternatives analysis completed by KPFF, Inc., dated January 2013 and titled “City of Eugene, Delta Ponds Trail Extension, Pedestrian Bridge Alternatives Analysis,” we understand scour and/or debris damage at this location is considered unlikely.

SITE DESCRIPTION

Site Conditions Our observations at the site and topographic information provided on the preliminary plans indicate the ground surface along the alignment varies from a high of about elevation 400 ft (NAVD 88) at the west end of the project area where the new trail meets the existing trail to a low of about elevation 386 ft near the east abutment of the proposed new bridge. The thalweg elevation at the bridge location is about elevation 381

ft. Existing slopes on the west side of the project area between where the new trail will connect with the existing trail and near the west abutment of the new bridge range from about 3H:1V to 2H:1V (Horizontal to Vertical). At the location of the planned pedestrian bridge abutments for the Debrick Slough crossing, the ground surface slopes downward toward the slough at approximately 5H:1V on the west side and is relatively flat on the east side. The proposed trail and boardwalk alignment are currently vegetated with grass, shrubs, and mature trees.

Geology Based on our review of the available geologic literature, our experience with other nearby projects, and the explorations made for this investigation, the trail alignment and pedestrian bridge site is mantled by Holocene-age alluvial deposits that typically consist of silt and sand near the surface and quickly grade to gravel with scattered cobbles. The relative density of the gravel is dense to very dense. The silt, sand, gravel, and cobbles were deposited in the active meander belt of the Willamette and McKenzie rivers and are referred to as Meander-Belt Alluvium (Madin and Murray, 2006). The existing pond structures were largely formed by past gravel mining.

SUBSURFACE CONDITIONS

General Subsurface materials and conditions along the trail alignment were investigated between June 10 and 19, 2019, with two machine-drilled borings, designated B-1 and B-2, and five hand-augured borings, designated HA-1 through HA-5. The machine-drilled borings were drilled to evaluate subsurface conditions at the proposed bridge bent locations, and were advanced to depths of about 40.5 to 60.8 ft. Due to limited drill rig access on the west side of the proposed bridge, boring B-1 was advanced south of the proposed bridge location at the western terminus of the existing trail. The hand-augered explorations were made along the trail alignment west of the slough and in the vicinity of the proposed boardwalk east of the slough and were advanced to depths of about 1 to 6.3 ft. The locations of the explorations are shown on Figure 2. The field and laboratory-testing programs completed for this project are described in Appendix A. Logs of the machine-drilled borings are shown on Figures 1A and 2A. Logs of the hand-augered borings are shown on Figures 3A through 5A. The terms used to describe the soils encountered in the explorations are defined in Table 1A and on the attached legend.

Machine-Drilled Borings For the purpose of discussion, the materials disclosed by the machine-drilled borings have been grouped into the following units based on their physical characteristics and engineering properties:

1. SILT

2. SAND, GRAVEL, and GRAVEL and COBBLES (Alluvium)

The following paragraphs provide a detailed description of these units and a discussion of the groundwater conditions at the site.

1. SILT. Boring B-1 encountered sandy silt at the ground surface extending to a depth of about 3.5 ft. The silt is brown and contains a trace of gravel and fine- to medium-grained sand. A Standard Penetration Test (SPT) N-value of 2 blows/ft indicates the relative consistency of the silt is soft.

2. SAND, GRAVEL, and GRAVEL and COBBLES (Alluvium). Alluvium consisting of sand, gravel, and gravel and cobbles was encountered interbedded beneath the silt in boring B-1 and alluvial gravel was encountered at the ground surface in boring B-2. The alluvium extends to the maximum depths explored of about 60.8 and 40.5 in borings B-1 and B-2, respectively. The sand alluvium is generally fine to coarse grained and contains varying percentages of silt and gravel ranging from some silt to silty and a trace of subrounded to rounded gravel to gravelly. The gravel and gravel and cobbles alluvium are generally subangular to rounded and contain a variable amount of fine- to coarse-grained sand and silt, ranging from some sand to sandy and some silt to silty. In boring B-1, scattered cobbles were encountered below a depth of about 20 ft and a layer of gravel and cobbles was encountered between a depth of about 35 and 39 ft. Although not encountered in the borings, boulders may be present in the alluvium. The relative density of the sand, gravel, and gravel and cobbles alluvium is medium dense to very dense based on SPT N-values of 19 blows/ft to 50 blows for less than 6 in. of sampler penetration (defined as practical refusal) and California-modified split-spoon sampler (CMS) SPT N*-values of 50 blows for less than 6 in. of sampler penetration and is typically dense to very dense. However, SPT N-values can overestimate the relative density in gravel, particularly when coarse gravel, cobbles, and/or boulders are present. The natural moisture content of the sand alluvium ranges from 22 to 25%.

Hand-Augered Borings Alluvial silt and/or sand were encountered mantling the ground surface in the hand-augered borings. Silt was encountered at the ground surface in hand-augered borings HA-1 through HA-3 and HA-5. The silt is brown and contains a variable sand content, ranging from a trace of fine-grained sand to sandy, and up to a trace of rounded gravel. Scattered cobbles are present in the silt and hand-augered borings HA-3 through HA-5 were terminated in the silt at depths of about 1 to 2 ft due to refusal on cobbles. The relative consistency of the silt is soft to medium stiff. The natural moisture content of the silt alluvium ranges from 13 to 22%.

Sand was encountered beneath the silt in hand-augered borings HA-1 and HA-2 and at the ground surface in HA-4. The sand is fine to medium grained and contains varying percentages of silt, ranging from some silt to silty, and a trace of rounded gravel. The relative density of the sand is loose. The natural moisture content of the sand alluvium ranges from 6 to 21%. Hand-augered borings HA-1, HA-2, and HA-4 were terminated in the sand at depths of 1 to 6.3 ft.

Groundwater Borings B-1 and B-2 were completed using mud-rotary drilling techniques, which do not permit the direct measurement of groundwater depths. Groundwater was not encountered in hand-augered borings. Based on our observations on site, we estimate the groundwater level at the site will approximate the water level in Debrick Slough. Groundwater levels are typically lowest between late summer and early fall.

CONCLUSIONS AND RECOMMENDATIONS

General The borings indicate the trail alignment is typically mantled with several feet of silt and sand alluvium underlain by relatively dense to very dense gravel with scattered cobbles to the maximum depth explored.

Groundwater at the site is anticipated to be at or near the level of the water in Debrick Slough. Scour is considered unlikely at the site. We anticipate foundation support for the bridge can be provided by spread footings established in structural fill or the relatively dense to very dense gravel underlying the site. The following sections of this report provide our conclusions and recommendations for design and construction of the project.

Seismic Considerations General. Based on the 2011 AASHTO SBD, bridges must be designed for a “low probability of collapse but may suffer significant damage and disruption to service” in response to a 1,000-year return interval earthquake (7% probability of exceedance in 75 years). The 1,000-year return interval “Life-Safety” criteria require bridge foundations to withstand the forces and soil displacements caused by the earthquake without collapse of any portion of the bridge structure.

Current Oregon Department of Transportation (ODOT) seismic design utilizing the AASHTO SBD evaluates earthquake-induced spectral accelerations for the 1,000-year return level “Life-Safety” earthquake using the 2014 U.S. Geological Survey (USGS) seismic hazard maps. The ground-motion parameters for the 1,000-year interval hazard level were obtained for the site’s coordinates of 44.0826° N latitude and -123.1055° W longitude using ODOT’s Excel spreadsheet application ODOT_ARS.v.2014.16. The AASHTO SBD methodology develops the design-level spectra for seismic analysis using two points at spectral periods of

0.2 and 1.0 second (SS and S1). The peak ground acceleration (PGA) and SS and S1 spectral values corresponding to the 1,000-year hazard level for the site are tabulated below. Based on site-class definitions provided in the AASHTO SBD, the bridge structure can be designed using Site Class C. Site factors FPGA, Fa, and Fv are then used with a site-class designation to adjust the bedrock spectral accelerations to ground-surface spectral accelerations. The following table includes the Site Class C seismic parameters recommended for the bridge site.

SPECTRAL VALUES AND SITE COEFFICIENTS

Hazard Level

Bedrock Spectral Values

Site Class C Site Coefficients

PGA, g Ss, g S1, g FPGA Fa Fv 1,000-year 0.23 0.48 0.22 1.20 1.30 1.50

Other Seismic Design Considerations. Based on the relatively dense to very dense gravel underlying the site, the potential for liquefaction at the site is very low. Based on the site topography, it is our opinion the risk of slope instability or lateral spreading resulting from seismic conditions is low. Based on the location of known and mapped faults in the area, we anticipate the potential for fault rupture or displacement at the site is low unless occurring on a previously unknown or unmapped fault. The risk of tsunami inundation and seiche at the site is absent.

Site Preparation and Grading The near-surface soils along the trail alignment consist primarily of silt and sand containing varying percentages of silt. The near-surface silt soils are sensitive to moisture content and are easily disturbed and softened by construction activities during wet-ground conditions and the contractor should use care to avoid disturbing the fine-grained subgrade. If possible, site preparation and earthwork should be accomplished during the normally dry summer months.

The ground surface should be stripped of the rooted zone within the limits of the improvements. Stripping to a depth of 4 to 6 in. will be necessary in vegetated areas, with deeper stripping and grubbing necessary where large shrubs or trees are present. The stripped materials are unsuitable for use as compacted structural fill. Following stripping or excavation to subgrade level, the resulting subgrade within the area of the improvements should be evaluated by a qualified geotechnical engineer and soft soils or areas of unsuitable material should be overexcavated and replaced with granular structural fill.

Final grading along the trail alignment should provide for positive drainage of surface water away from exposed slopes to minimize erosion. Temporary excavation slopes should be made no steeper than about 1H:1V and permanent cut and structural fill slopes should be no steeper than 2H:1V. In general, structural fills should extend a minimum horizontal distance of 3 ft beyond the limits of the new improvements.

Recommended setbacks for retaining walls are discussed in the Retaining Walls section of this report.

Off-road access will be required to construct the bridge foundations and will likely require access roads and work pads. We anticipate access roads and work pads constructed with crushed rock, such as 3- or 4-in.-minus rock and having a thickness between 12 and 24 in., will be required to support construction equipment and minimize subgrade disturbance depending on the type and weight of the equipment and subgrade conditions. If the subgrade is particularly soft, it may be prudent to place a geotextile fabric (Mirafi 500X or equivalent) on the subgrade as a separation membrane prior to placing and compacting the granular work pad.

Structural Fill We anticipate cut and fill heights/thicknesses will be typically less than about 4 ft. All fill installed along the trail alignment should be placed as structural fill and, in our opinion, the silt, sand, and gravel that mantle the site are suitable for use in constructing structural fills. In this regard, cut portions of the alignment may represent a potential source of fill material. However, fine-grained soils are sensitive to moisture content and can only be placed and adequately compacted during the dry summer months. During the wet winter and spring months, all fills should be constructed using imported, relatively clean, crushed rock. Any fill placed on slopes steeper than 6H:1V should be placed on minimum-4-ft-wide flat benches excavated into firm ground. New fill should be overbuilt laterally 1 to 2 ft and trimmed back to finished grades with a smooth-edged excavator bucket to form a firm surface.

Approved organic-free, fine-grained soils used to construct structural fills should be placed in 9-in.-thick lifts (loose) and compacted using a segmented-pad roller to a density not less than 95% of the maximum dry density determined by ASTM International (ASTM) D698. The moisture content of fine-grained soils at the time of compaction should be controlled to within 3% of optimum. Some aeration and drying of the on-site fine-grained soils may be required to meet the recommended compaction criteria. Fill placed in landscaped areas should be compacted to at least 90% of the maximum dry density determined by ASTM D698.

Imported granular material used to construct general structural fills should consist of well-graded crushed rock with a maximum size up to about 3 in. and containing less than about 8% passing the No. 200 sieve (washed analysis). Granular structural fill should be placed in horizontal lifts and compacted to at least 95% of the maximum dry density determined by ASTM D698. Compaction of granular soil should be completed with adequately sized, vibratory compaction equipment. Loose-lift thicknesses should not exceed 12 in. for heavy-weight compaction equipment and thinner lifts may be required for lighter equipment. Actual lift thicknesses to achieve the required compaction should be evaluated based on field moisture-density testing completed at the time of fill placement. Field density testing is not practical for materials with particle sizes greater than about 1½ in. and should be evaluated by visual methods.

Bridge Foundation Support General. The ground surface in the vicinity of proposed bridge has slopes of about 5H:1V on the west side and is relatively flat on the east side. The bridge site is mantled with up to about 2 ft of silt near the west end of the bridge. Beneath the silt on the west side and at the ground surface on the east side, the site is underlain by relatively dense to very dense alluvial gravel and cobbles. The unfactored design load at each abutment is estimated at 50 kips.

In our opinion, for the subsurface conditions and loads anticipated, conventional spread foundations established in medium-dense to dense granular soils or structural fill will be the most appropriate alternative to support the new bridge. The presence of cobbles and possible boulders may make installation of deep foundations challenging. The following sections provide our recommendations for bridge-foundation support utilizing spread footings.

Spread Footings. We understand bridge abutment foundations will be designed in accordance with the AASHTO BDS. The following soil parameters may be used for bridge foundations established on medium-dense to dense alluvial gravel and cobbles or imported granular structural fill.

FOUNDATION DESIGN PARAMETERS

Effective Friction Angle 35°

Effective Cohesion, psf 0

Total Unit Weight, pcf 130

Buoyant Unit Weight, pcf 68

In accordance with the AASHTO BDS, resistance factors must be applied to the nominal bearing resistance, nominal sliding resistance, and nominal passive resistance for spread footing design. The recommended resistance factors for footing design are summarized in the following table.

RESISTANCE FACTORS FOR SPREAD-FOOTING DESIGN

Spread Footing Resistance Factors

Strength

Limit State Service

Limit State Extreme

Limit State Bearing Resistance 0.45 1.00 1.00

Sliding Resistance (Cast-in-Place Concrete) 0.80 1.00 1.00

Passive Component of Sliding Resistance 0.50 1.00 1.00

In our opinion, spread footings established in the alluvial gravel and cobbles soil or granular structural fill can be designed for nominal bearing resistances of 15, 15, and 5 ksf for the strength, extreme, and service limit states, respectively. The footing width should be at least 4 ft and the bases of the footings should be established at a minimum depth of 2 ft below the lowest adjacent finished grade and provide for a minimum horizontal setback of at least 10 ft from the finished slope. This is appropriate for slopes at 5H:1V or flatter.

We recommend the bridge footings be underlain by a minimum-6-in.-thick layer of compacted crushed rock with a maximum size up to about 1 in. and containing less than about 8% passing the No. 200 sieve (washed analysis). Areas with loose, disturbed native granular subgrade should be compacted prior to placement of the 6-in.-thick crushed-rock section. The crushed rock should extend at least 12 in. beyond the edges of the footing. Depending somewhat on the time of year construction takes place, dewatering of the footing excavations may be required. Groundwater can typically be controlled by pumping from sumps in the excavation bottom. To facilitate dewatering, it may be appropriate to overexcavate the footing and install a drainage layer of clean, crushed rock of up to 2-in. maximum size with not more than 2% passing the No.

200 sieve (washed analysis). We anticipate the thickness of the drainage layer would be at least 1 ft thick.

Horizontal shear forces can be resisted partially or completely by frictional forces developed between the bases of the footing and the underlying soil. The total frictional sliding resistance between the footing and the soil is the normal force times the coefficient of friction between the soil and the base of the footing. We recommend a nominal value of 0.45 for the coefficient of friction for concrete footings constructed on compacted crushed rock.

Additional resistance to sliding may be available from soil passive pressure against the embedded portions of foundations. Due to the potential for bank erosion along the slough, we recommend the foundation design for bridge foundations not rely on the passive pressure of the embedded portion of the abutment/footing in front of the slough to resist sliding. If the passive earth pressure against the embedded portion of the bridge abutment/footing is used to resist sliding, we recommend computing this resistance on the basis of an equivalent fluid having unit weights of 250, 500, and 500 pcf (nominal passive resistance) for the service, strength, and extreme limit states, respectively, where the ground surface is flat in front of the footing. For foundations constructed on slopes up to 3H:1V, the passive pressure against embedded portion of the footing should be reduced to 150, 300, and 300 pcf (nominal passive resistance) for the service, strength, and extreme limit states, respectively. This design passive earth pressure would be applicable only if the abutment footing is cast neat against undisturbed soil and/or if backfill for the footings and the abutment is placed as granular structural fill.

All spread footing excavations should be observed by a qualified geotechnical engineer. Areas of soft or otherwise unsuitable material encountered at subgrade elevation should be removed and replaced with compacted crushed rock in accordance with the Structural Fill section of this report. If groundwater is encountered in the footing excavation, it should be removed prior to placing concrete.

Retaining Walls General. As previously discussed, gravity block retaining walls less than 4 ft in height will be used for support of the trail alignment along the west side of the slough. In our analyses, we assumed the minor retaining walls on the west side of the slough will not be designed for seismic loading; however, abutments and wing walls of the bridge will be designed for seismic loading.

Wall Construction. Based on a review of trail cross sections shown on the preliminary plans, we anticipate the majority of the retaining walls will be constructed in areas where the angle of the slope is on the order of 3H:1V to 2H:1V. For areas where the ground line in front of the wall will be nearly horizontal, we recommend the toe of the wall be setback a horizontal distance of at least 5 ft from the face of the adjacent finished slope and have a minimum embedment of at least 1.5 ft below finished grades. For walls founded on slopes of 3H:1V to 2H:1V, we recommend the base of the wall foundation be provided with a minimum of 2 and 2.5 ft of embedment, respectively, to provide a distance of 5 ft from the face of the adjacent finished slope. In general, temporary excavations to complete construction of the walls should be sloped at no steeper than 1H:1V.

The explorations made along the proposed alignment on the west side of the slough indicate the alignment is generally underlain with soft to medium-stiff silt. Due to the potential of encountering soft soil, it should be anticipated that some amount of overexcavation of unsuitable soil and replacement with granular structural fill at the wall subgrade will be necessary. Overexcavation, if necessary, should extend horizontally beyond the edge of the foundation at least one-half of the depth of overexcavation. Granular backfill should consist of imported granular material as discussed above in the Structural Fill section. The backfill should be compacted as structural fill to at least 95% of the maximum dry density determined by ASTM D698 (standard Proctor). Ponded water in excavations, if present, should be removed prior to placement and compaction of backfill.

Retaining Wall Foundation Design Parameters. Based on the materials encountered in the explorations, we anticipate the walls will be founded in alluvial silt and sand. Soft or organic soils encountered at the base of the wall should be overexcavated and backfilled with granular structural fill. Design parameters used in design of the gravity block walls are included in the following table.

DESIGN PARAMETERS

Foundation Backfill Effective Friction Angle 30° 35°

Effective Cohesion, psf 0 0

Unit Weight, pcf 110 125

In accordance with AASHTO BDS, resistance factors must be applied to the nominal bearing resistance and nominal sliding resistance for gravity block wall design. The recommended resistance factors for the strength and service limits strengths are provided in the table below. Based on our review of Section 11.5.4.2 of AASHTO BDS, we anticipate the gravity block walls will not be designed for the extreme limit state.

RESISTANCE FACTORS FOR PERMANENT GRAVITY WALLS

Spread Footing Resistance Factors

Strength

Limit State Service

Limit State Bearing Resistance 0.55 1.00

Sliding Resistance 1.00 1.00

Foundation loads for the retaining walls are not available at this time, though we anticipate they will be relatively small. In our opinion, gravity block walls established in silt or sand can be designed for a nominal bearing resistance of 4 and 1.5 ksf for the strength and service limit states, respectively. We recommend wall foundations have a width of at least 2 ft. We estimate static settlements of foundations designed and constructed as recommended above will be less than 1 in.

Horizontal shear forces can be resisted partially or completely by frictional forces developed between the bases of the footings and the underlying soil and by soil passive resistance. The total frictional resistance between the footing and the soil is the normal force times the coefficient of friction between the soil and the base of the footing. We recommend ultimate values of 0.30 and 0.45 for the coefficient of friction for concrete footings constructed on silt and sand or crushed rock, respectively. The normal force is the sum of the vertical forces (dead load plus real live load). If additional lateral resistance is required, passive earth pressures against embedded footings can be computed as described above for spread footings.

Lateral Earth Pressures. Design lateral earth pressures for retaining walls depend on the type of construction, i.e., the ability of the wall to yield. Possible conditions are: 1) a wall that is laterally supported at its base and/or top and therefore is unable to yield to the active state, and 2) a retaining wall, such as a typical cantilever or gravity wall that yields to the active state by tilting about its base.

We anticipate the retaining walls for the trail can be considered yielding walls. Yielding walls may be designed using a lateral earth pressure from the backfill computed based on equivalent fluid unit weights of 35, 45, and 55 pcf for flat backslopes, backslopes sloped at 3H:1V, and backslopes sloped at 2H:1V, respectively. Non-yielding walls, such as the abutments for the pedestrian bridge, may be designed using a lateral earth pressure from the backfill computed based on an equivalent fluid unit weight of 50 pcf for approximate flat-backfill conditions. These values assume completely drained wall backfill.

Wall drainage can be provided by a minimum-12-in.-wide vertical drainage blanket consisting of clean, crushed rock of up to 1½-in. maximum size with not more than 2% passing the No. 200 sieve (washed analysis). Open-graded crushed rock, such as ¾- to 1½-in., crushed rock (drain rock), is commonly used for this purpose. A non-woven geotextile, such as Mirafi 140N or similar, should be placed between the open-graded crushed rock and the surrounding silt soil and/or common backfill to reduce migration of fines into the drainage blanket. A perforated drainpipe without a geotextile sock should be placed at the base of the drainage blanket. The drainpipes should collect into a non-perforated pipe extending to the base of the slope. To avoid inducing excessive lateral pressure against the wall, the backfill behind the walls should be compacted to between 93 to 95% of the maximum density determined by ASTM D698 using hand-operated equipment.

Any additional lateral pressures due to surcharge loads, such as construction traffic loads or stockpiles of material, behind the walls may be estimated using the guidelines shown on Figure 3. If seismic design of a structure is required, additional lateral loads due to seismic forces can be evaluated by increasing the equivalent fluid pressures given for the static conditions by 20%. The temporary live-load surcharges do not need to be included in the seismic-load case.

Boardwalk Diamond Pier® Foundations. A portion of the trail segment east of the pedestrian bridge will consist of several hundred feet wooden boardwalk. Diamond Pier® foundations have been used in the past throughout the site and, in our opinion, can be used at this location as well. Diamond Pier® foundations are a proprietary system in which galvanized steel pipes are installed through a pre-cast, concrete pier pad placed on the ground surface. The pipes are then driven to a maximum depth of about 5 ft.

Diamond Pier® foundations are typically designed and installed by specialty contractors. It should be assumed that the groundwater will reach the ground surface. Hand-augered borings HA-4 and HA-5 completed in the vicinity of the proposed boardwalk encountered relatively soft and/or loose silt and sand to a depth of about 1 ft, underlain by relatively dense gravel and cobbles. In this regard, we recommend neglecting the capacity in the upper approximately 1 ft of the soil profile to account for this soft material and potential disturbance during construction. We understand the soil parameters required for design of the of Diamond Pier® foundations include the effective angle of internal friction, φ’; soil cohesion, c; and soil total unit weight, γT. For the soils below the unsuitable soils, the following parameters can be assumed for design:

φ’ = 35°, c = 0 psf, and γT = 130 pcf. Settlement estimates for the Diamond Pier® foundations should be developed by the designer of the proprietary foundation based on anticipated loads for each foundation element.

DESIGN REVIEW AND CONSTRUCTION SERVICES

We welcome the opportunity to review and discuss construction plans and specifications for this project as they are being developed. In addition, GRI should be retained to review all geotechnical-related portions of the plans and specifications to evaluate whether they are in conformance with the recommendations provided in this report. In addition, to observe compliance with the intent of our recommendations, the design concepts, and the plans and specifications, we are of the opinion all construction operations dealing with earthwork and foundations should be observed by a GRI representative. Our construction-phase services will allow for timely design changes if site conditions are encountered that are different from those described in our report. If we do not have the opportunity to confirm our interpretations, assumptions, and analyses during construction, GRI cannot be responsible for the application of our recommendations to subsurface conditions different from those described in this report.

LIMITATIONS

This report summarizes the results of our subsurface explorations and laboratory-testing programs and provides our conclusions and recommendations regarding the design and construction of the proposed project. The scope is limited to the specific project and location described herein, and our description of the

Renews 12/2020 project represents our understanding of the significant aspects of the project relevant to earthwork and the design and construction of the proposed trail extension, pedestrian-bridge foundations, and boardwalk. In the event any changes in the design and location of the improvements as outlined in this report are planned, we should be given the opportunity to review the changes and modify or reaffirm the conclusions and recommendations of this report in writing.

The conclusions and recommendations submitted in this report are based on the data obtained from the explorations made at the locations indicated on Figure 2 and other sources of information discussed in this report. In the performance of subsurface investigations, specific information is obtained at specific locations at specific times. However, it is acknowledged variations in soil conditions may exist between exploration locations, and this report does not necessarily reflect these variations. The nature and extent of variation may not become evident until construction. If, during construction, subsurface conditions differ from those encountered in the explorations, we should be advised at once so we can observe and review these conditions and reconsider our recommendations where necessary.

Submitted for GRI, Michael W. Reed, PE, GE Tamara G. Kimball, PE, GE Principal Senior Engineer

References

American Association of State Highway Transportation Officials (AASHTO), 2011, Guide specifications for LRFD seismic bridge design, 2nd edition.

AASHTO, 2017, LRFD bridge design specifications, 8th edition.

AASHTO, 2009, LRFD guide specifications for the design of pedestrian bridges, 2nd edition.

Oregon Department of Transportation, 2019, Bridge design manual.

Oregon Department of Transportation, 2018, Standard specifications for construction.

Madin, I. P., and Murray, R. B., 2006, Preliminary geologic gap of the Eugene east and Eugene west quadrangles, Lane County, Oregon, Oregon Department of Geology and Mineral Industries, Open File Report OFR 0-06-17.

This document has been submitted electronically.

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OCT. 2019 JOB NO. 6247 FIG. 1

0 1/2 1 MILE

North

USGS TOPOGRAPHIC MAP

EUGENE-EAST, OREG. (2017)

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SITE PLAN

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0 120 FT

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APPENDIX A

Field Explorations and Laboratory Testing

A-1

APPENDIX A

FIELD EXPLORATIONS AND LABORATORY TESTING

FIELD EXPLORATIONS

General Subsurface materials and conditions near the planned improvements were investigated by GRI between June 10 and 19, 2019, with two machine-drilled borings, designated B-1 and B-2, and five hand-augured borings, designated HA-1 through HA-5. The machine-drilled borings were advanced to depths of about 40.5 to 60.8

ft. The hand-augered borings were advanced to depths of about 1 to 6.3 ft. The locations of the explorations are shown on Figure 2.

Machine-Drilled Borings Borings B-1 and B-2 were advanced to depths of about 40.5 to 60.8 ft with mud-rotary drilling techniques using a truck-mounted drill rig provided and operated by Western States Soil Conservation, Inc., of Hubbard, Oregon. Disturbed soil samples were typically obtained at 2.5-ft intervals of depth in the upper 15 ft and at 5-ft intervals below this depth. Disturbed samples were obtained using a standard split-spoon sampler. The soil samples obtained in the split-spoon sampler were carefully examined in the field and representative portions were saved in airtight jars for further examination and physical testing in our laboratory. At the time of sampling, the Standard Penetration Test (SPT) was conducted. This test consists of driving a standard split-spoon sampler into the soil or rock a distance of 18 in. using a 140-lb hammer dropped 30 in. The number of blows required to drive the sampler the last 12 in. is known as the Standard Penetration Resistance, or SPT N-value. SPT N-values provide a measure of the relative density of granular soils and the relative consistency of cohesive soils. Additionally, a larger-diameter California-modified split-spoon sampler (CMS) having an outside diameter of 3 in. was used to collect samples of the coarse-grained deposits. The number of blows required to drive the CMS the last 12 of 18 in. is denoted as the SPT N*-value.

The drilling was directed and observed by a member of GRI’s geotechnical engineering staff, who maintained a detailed log of the conditions and materials encountered during the work. Logs of the drilled borings are provided on Figures 1A and 2A. The logs present a descriptive summary of the various types of materials encountered in the boring and note the depths at which the materials and/or characteristics of the materials change. To the right of the descriptive summary, the numbers and types of samples are indicated. Farther to the right, SPT N-values are shown graphically, along with the natural moisture content. The terms used to describe the materials encountered in the borings are defined in Table 1A.

Hand-Augered Borings Five hand-augered borings were advanced by GRI to depths between about 1 and 6.3 ft. Grab samples from the hand-augered borings were obtained from the cuttings, placed in airtight jars, and returned to GRI’s laboratory for further classification and testing. The borings were backfilled with the excavated materials.

Logs of the hand-augered borings are provided on Figures 3A through 5A.

LABORATORY TESTING

The samples obtained from the borings were examined in our laboratory, where the physical characteristics of the samples were noted and field classifications modified where necessary. At the time of classification, A-2 the natural moisture content of each non-gravel sample was determined. Laboratory-test results are summarized in Table 2A and on Figures 1A and 3A through 5A.

Table 1A: GUIDELINES FOR CLASSIFICATION OF SOIL

Relative Density for Granular Soil

Standard Penetration Resistance Relative Density (N-values), blows per ft very loose 0 - 4 loose 4 - 10 medium dense 10 - 30 dense 30 - 50 very dense over 50

Consistency for Fine-Grained (Cohesive) Soil

Standard Penetration Torvane or Resistance (N-value), Undrained Shear

Consistency blows per ft Strength, tsf very soft 0 - 2 less than 0.125 soft 2 - 4 0.125 - 0.25 medium stiff 4 - 8 0.25 - 0.50 stiff 8 - 15 0.50 - 1.0 very stiff 15 - 30 1.0 - 2.0 hard over 30 over 2.0

Grain-Size Classification Modifier for Subclassification

Boulders Percentage of >12 in. Other Material Adjective In Total Sample Cobbles 3 - 12 in. clean 0 - 2

Gravel trace 2 - 10 1/4 - 3/4 in. (fine) 3/4 - 3 in. (coarse) some 10 - 30

Sand sandy, silty, 30 - 50 No. 200 - No. 40 sieve (fine) clayey, etc.

No. 40 - No. 10 sieve (medium) No. 10 - No. 4 sieve (coarse)

Silt/Clay - pass No. 200 sieve

B-1 S-6 25.0 376.0 25 -- -- -- -- SAND

S-9 40.0 361.0 22 -- -- -- -- SAND

HA-1 S-1 2.0 396.0 18 -- -- -- -- SILT

S-2 4.0 394.0 11 -- -- -- -- SAND

S-3 5.0 393.0 6 -- -- -- -- SAND

S-4 5.8 392.3 13 -- -- -- -- SAND

HA-2 S-1 2.0 395.0 22 -- -- -- -- SILT

S-2 3.0 394.0 11 -- -- -- -- SAND

HA-3 S-1 1.5 387.5 14 -- -- -- -- SILT

HA-4 S-1 0.5 386.5 21 -- -- -- -- SAND

HA-5 S-1 0.5 388.5 13 -- -- -- -- SILT

SUMMARY OF LABORATORY RESULTS

Elevation, ftDepth, ftSampleLocation

Table 2A

Sample Information Dry Unit

Weight, pcf Liquid

Limit, % Plasticity Index, %

Moisture Content, %

Fines Content, %

Atterberg Limits

Soil Type

Groundwater level after drilling and date measured

Groundwater level during drilling and date measured

Flush-mount monument set in concrete

Symbol

Concrete, well casing shown where applicable

Symbol Description

Symbol

FIELD MEASUREMENTS

Sandy GRAVEL; clean to some silt and clay

GRAVEL; clean to some silt, clay, and sand

Silty SAND; up to some clay and gravel

CLAY; up to some silt, sand, and gravel

Gravelly CLAY; up to some silt and sand

Sandy CLAY; up to some silt and gravel

Silty CLAY; up to some sand and gravel

Vibrating-wire pressure transducer

BEDROCK SYMBOLS

Symbol

FILL

Typical Description

BASALT

MUDSTONE

Rock quality designation (RQD, %)

3.0-in. O.D. split-spoon sampler with recovery

(ASTM D3550)

Grab Sample

Rock core sample interval

SOIL SYMBOLS

Geoprobe sample interval

INSTALLATION SYMBOLS

Grout, inclinometer casing shown where applicable

Bentonite seal, well casing shown where applicable

Grout, vibrating-wire transducer cable shown where applicable

LANDSCAPE MATERIALS

PEAT

Silty GRAVEL; up to some clay and sand

Clayey GRAVEL; up to some silt and sand

Clayey SAND; up to some silt and gravel

SILT; up to some clay, sand, and gravel

Gravelly SILT; up to some clay and sand

Sandy SILT; up to some clay and gravel

Clayey SILT; up to some sand and gravel

Gravelly SAND; clean to some silt and clay

SAND; clean to some silt, clay, and gravel

1-in.-diameter solid PVC

Symbol

BORING AND TEST PIT LOG LEGEND

Typical Description

Shelby tube sampler with recovery

(ASTM D1587)

SAMPLER SYMBOLS

Symbol

2.0-in. O.D. split-spoon sampler and Standard Penetration Test with recovery (ASTM D1586)

Sampler Description

Sonic core sample interval

Filter pack, machine-slotted well casing shown where applicable

1-in.-diameter hand-slotted PVC

Typical Description

SILTSTONE

SANDSTONE

SURFACE MATERIAL SYMBOLS

Symbol Typical Description

Portland cement concrete PAVEMENT

Crushed rock BASE COURSE

Asphalt concrete PAVEMENT

Rock core recovery (%)

B O

R

IN

G A

N D

T E

S T

P

IT

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G L

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D G

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Sandy SILT, trace gravel, brown, soft, fine- to medium-grained sand

GRAVEL, some fine- to coarse-grained sand to sandy, some silt to silty, brown, medium dense, subrounded to rounded

---very dense below 10 ft

---gray, scattered cobbles below 20 ft

SAND, some silt, trace subrounded to rounded gravel, brown, dense, fine to coarse grained ---some gravel to gravelly, some silty to silty below

25.5 ft

---silty, gravelly below 30 ft

GRAVEL and COBBLES, some fine- to coarse-grained sand to sandy, some silt to silty, brown, very dense, rounded

Driller notes sandy materials and smooth drilling in upper 3 ft Driller notes material change at 3.5 ft

Driller notes material change at 39 ft

PLASTIC LIMIT, %

LIQUID LIMIT, %

FINES CONTENT, %

BLOWS PER FOOT

MOISTURE CONTENT, %

Mud Rotary

Drilled by:

140 lb Drop:

Not AvailableSee Legend for Explanation of Symbols

D

EP

TH

, F

T

BL

O

W C

O U

N T

Date Started:

Note:

N. Utevsky Western States Soil Conservation, Inc.

Equipment:

EL

EV

AT

IO

N , F

T D

EP

TH

, F T

Auto Hammer

Hole Diameter:

CLASSIFICATION OF MATERIAL

Energy Ratio:

SA

M

PL

E

N O

CME 55 HT Track-Mounted Drill Rig

Surface Elevation:

(CONTINUED NEXT PAGE)

Hammer Type:

1.0

Weight:

401.0 ft [±] (NAVD 88) IN

ST

AL

LA

TI

O

N

0.5

Logged By:

Drilling Method:

6/10/19

IN

ST

AL

LA

TI

O

N

BORING B-14 in. 30 in.

FIG. 1A

TORVANE SHEAR STRENGTH, TSF

UNDRAINED SHEAR STRENGTH, TSF

SA

M

PL

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PE

G R

AP

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IC

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O G

COMMENTS AND

ADDITIONAL TESTS

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