Saddle_Road_East_Side.Geotech_Design_Tech_Memo.pdf

TECHNICAL MEMORANDUM

HI SR 200(3)

SADDLE ROAD – EAST SIDE

MILEPOST 11 to MILEPOST 5.6

HAWAII COUNTY

W.O. 4984‐40 AUGUST 31, 2015

Prepared for

OKAHARA & ASSOCIATES, INC.

and

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

CENTRAL FEDERAL LANDS HIGHWAY DIVISION

GEOLABS, INC.

Geotechnical Engineering and Drilling Services

TECHNICAL MEMORANDUM

HI SR 200(3)

SADDLE ROAD – EAST SIDE

MILEPOST 11 TO MILEPOST 5.6

HAWAII COUNTY

W.O. 4984‐40 AUGUST 31, 2015

Prepared for

OKAHARA & ASSOCIATES, INC.

and

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

CENTRAL FEDERAL LANDS HIGHWAY DIVISION

THIS WORK WAS PREPARED BY

ME OR UNDER MY SUPERVISION.

4‐30‐16

SIGNATURE EXPIRATION DATE

OF THE LICENSE

Geotechnical Engineering and Drilling Services 2006 Kalihi Street • Honolulu, HI 96819

Hawaii • California

GEOLABS, INC. TECHNICAL

Geotechnical Engineering and Drilling Services MEMORANDUM

2006 Kalihi Street • Honolulu, Hawaii 96819

Phone: (808) 841-5064 • Facsimile: (808) 847-1749 • E-mail: hawaii@geolabs.net Hawaii • California

DATE: August 31, 2015 @ 4:59 PM W.O. No.: 4984-40 TO: Okahara & Associates, Inc. FROM: Robin M. Lim / Timothy T. Roy ATTN: Mr. Bruce Meyers NO. OF PAGES: 17 (text) + 4 (plates) SUBJECT: Technical Memorandum Saddle Road – East Side, HI SR 200(3) E-MAIL: bmeyers@okahara.com COPY TO: File / Original

This technical memorandum presents our geotechnical recommendations for the design of the Saddle Road – East Side project on the Island of Hawaii.

A report of our findings from the geotechnical exploration of the project site is contained in the report entitled “Geotechnical Data Report, Hawaii State Route 200 (Saddle Road), Milepost 11 to Milepost 5.6, Saddle Road East Side, Island of Hawaii” dated July 2, 2015. The geotechnical data report contained detailed descriptions of the materials encountered in the borings and the results of the laboratory tests performed on selected samples for this project.

Project Considerations

The Saddle Road East Side project site is located on the coalesced easterly facing slopes of the Mauna Kea and Mauna Loa Volcanoes. The new roadway is proposed to extend between about Milepost 11 of the existing Saddle Road alignment (several miles westerly from the residential area of Kaumana) and about Milepost 5.6 (near the top of the Puainako Street Extension). The proposed road alignment traverses basaltic rock terrain that slopes and rolls variably down toward the east from the western end of the project site. Ground surface elevations range from about +2,850 feet Mean Sea Level (MSL) at the western end of the roadway alignment (Milepost 11) to approximately +1,340 feet MSL at the eastern end of the alignment near the existing Milepost 5.6.

The length of the new Saddle Road East Side Alignment between Milepost 11 and Milepost 5.6 is approximately 5.4 miles and generally follows the existing roadway corridor with the exception of some lateral offsets from the existing roadway and realignment (straightening) of some of the existing roadway curves. In addition to the roadway, several new box and pipe culverts will be constructed to aid with drainage along the realigned portion of the roadway.

Existing Site Conditions

The existing Saddle Road within the project limits consists of two-lanes with a paved asphaltic concrete roadway surface. The existing paved roadway surface appears to be in generally fair to good condition. The existing travel lanes are approximately 10 feet wide with additional paved shoulder extending about 3 to 4 feet

Technical Memorandum Page 2 Saddle Road – East Side HI SR 200(3) W.O. 4984-40 August 31, 2015 @ 4:59 PM beyond the white stripe. The unpaved grassed shoulder typically is on the order of about 6 to 8 feet wide on each side of the roadway. The existing roadway contains numerous horizontal and vertical curves that generally follow the natural rolling hill slope topography. Based on our observations, earth cuts and fills located along the existing Saddle Road alignment are limited and generally are less than approximately 1 to 5 feet in height.

Based on our observations, the surface topographic relief of the native pahoehoe lava flows generally is low with some scattered rock formation irregularities consisting of partially collapsed lava flow channels, lava flow pressure ridges, localized shallow open pits, and open cracks and crevices. Ripping of the near-surface pahoehoe lavas using a Komatsu D275 bulldozer (work associated with installing access trails for drill rig access) encountered hard to occasionally very hard rock zones producing rock fragments typically on the order of about 1 to 2 feet in dimension with little fines.

Most of the roadside terrain along the existing Saddle Road alignment exists as undeveloped forested rock land. There is an overhead power transmission line alignment with associated utility poles, which approximately parallels the existing Saddle Road alignment. Multiple roadside vehicle trails exist in the vicinity of the utility easement to provide access to the utility poles from the roadway. The access trails appear to have been rough-graded by a bulldozer (by others).

Based on our site reconnaissance, existing structures such as retaining walls, bridges, and culverts were not observed within the project limits. The earthwork construction performed for this portion of the existing Saddle Road appears to have consisted of very limited cut and fill grading, essentially following the natural land surface contour where possible. Therefore, existing cut slopes and large fill embankments generally were not observed along the existing Saddle Road alignment.

Established stream channel and natural drainage gully features could not be identified on the relatively young, porous basalt rock surfaces that cover the project site.

Anticipated Subsurface Conditions

The following discussion provides a general description of the anticipated subsurface conditions at the project site. A more detailed description of the subsurface conditions encountered is presented in the aforementioned data report for this project.

Based on our site reconnaissance, fill materials are believed to exist throughout the length of the existing Saddle Road alignment. The recent fills are associated with the original construction of the Saddle Road. The fills generally consist of various basaltic cobbles and boulders with some sands and gravel. The location of the recent fill is assumed to exist along the entire length of the existing Saddle Road East Side Alignment within the existing roadway prism. Based on our observations, the existing Saddle Road alignment was constructed with limited cut and fill earthwork and generally followed the pre-existing grades of the natural terrain. The typical depth of recent fills

Technical Memorandum Page 3 observed along the existing Saddle Road alignment appears to be on the order of about 1 to 3 feet with some localized deeper fills.

Pahoehoe type lava is encountered most commonly throughout the project site.

The observed surface exposures of pahoehoe basalt rock are typified by relatively smooth, low relief hummocks separated by open fractures that penetrate several feet into the surface of the lava flow. Some scattered pockets of loose, rocky rubble mounds are interspersed across the flow surface.

Based on our evaluation, the individual pahoehoe lava flows may range from about 3 to 15 feet thick. The pahoehoe lava flows may be separated from the adjacent pahoehoe flows by generally very thin clinker seams of about 1 to 3 feet thick. The pahoehoe lava flows typically are composed of medium hard to very hard basalt rock ranging from closely fractured to slightly fractured in character. Pahoehoe lavas typically contain buried cavities and/or voids associated with the movement of magma and cooling of the more fluid lavas. The voids may consist of large, continuous lava tube features or isolated blister pockets.

Excavation of pahoehoe generally involves hard rock excavation methods, which may include blasting, and the materials produced typically consist of boulders and larger blocks of rock. In general, the hardness of pahoehoe basalt may be estimated by the degree of inter connecting vesicularity (small, shallow, textural pits derived from exsolving gases during the cooling of magma) with the softer rock usually being less dense (more porous), as a result of the higher degree of vesicle density. A highly vesicular pahoehoe rock is usually less hard than slightly vesicular rock. The term “scoriaceous” is defined as highly-vesicular texture to the point of almost being pumice-like in character. Scoriaceous rock is often representative of clinker materials that may be associated with the upper and lower boundaries of individual pahoehoe lava flows.

A’a basalt typically consists of thicker individual lava flow units composed of a substantial surface layer of clinker rubble overlying a dense core of massive basalt material. The clinker rubble generally consists of a loose to moderately consolidated accumulation of basalt rock fragments ranging from gravel and cobble size materials to some large blocks and plates of rubble on the order of about 5 to 10 feet in diameter.

The clinker typically is very porous and may be consolidated to a lower volume by traversing the clinker surface with heavy construction equipment, such as a heavy bulldozer. The clinker materials generally may break down readily to cobble and small boulder size fragments with limited processing by heavy construction equipment making the material a good source of suitable fill material. The in-situ clinker materials are very porous because of the large amount of void space that occurs between the individual clinker rock fragment components.

Beneath the clinker surface, which may extend between 5 feet to over 15 feet in thickness, generally hard to very hard basalt rock may be encountered with massive rock seams on the order of about 10 feet to over 20 feet in thickness. The hard, massive

Technical Memorandum Page 4 rock seam represents the interior lava flow core covered beneath a blanket of clinker and sometimes a lower and typically thinner bounding clinker layer representing the bottom of the individual a’a lava flow unit. The hardened basalt rock contained below the clinker layer may be massive to moderately fractured and difficult to excavate.

Excavations encountering the a’a flow core material typically produce large blocks of intact hard rock that typically require additional processing (crushing) for use as suitable fill material. Substantially thick buried layers of massive rock may require the use of blasting to excavate the materials.

Surface volcanic ash soils were encountered along the portion of alignment between about Station 1742+00 through about Station 1864+00. The volcanic ash, generally consisting of clayey silt material with some fine sand, may be soft to medium stiff and very moist to wet in the native depositional environment. The soils are believed to range in thickness between about 10 and 15 feet and may be encountered exposed at the ground surface or buried beneath a veneer of basalt rock that may range from several feet to greater than about 20 feet thick. It should be noted that volcanic ash deposits are typically soft and susceptible to appreciable settlements when loaded. A summary of the surface ash deposits is presented on Plate 1 for ease of reference.

Based on the subsurface conditions anticipated at the project site, detailed discussions and geotechnical recommendations for the new roadway design and construction are presented in the following sections herein.

Earthwork Requirements

Based on the existing topography at the project site and the grading plan, earthwork for the project will involve excavations up to about 24 feet deep and embankments up to about 32 feet thick to construct the new roadway. Due to the presence of relatively compressible surface volcanic ash along portions of the project alignment, the site preparation work for cut subgrades and areas designated to receive fills will be designed using two different scenarios – areas with 3 feet or less of surface volcanic ash (about Station 1545+00 to Station 1795+00) and areas with greater than 3 feet of surface volcanic ash (about Station 1795+00 to Station 1864+00). It should be noted that localized pockets of ash thicker than 3 feet may be encountered between Station 1730+00 and Station 1795+00. The above stationing is approximate and may need to be modified in the field based on the exposed conditions.

In general, grading work should conform to the Standard Specifications for the Construction of Roads and Bridges on Federal Highway Projects (FP-03) and the site-specific recommendations contained in this technical memorandum. Items of site grading that are addressed in the subsequent subsections include the following:

1. Site Preparation

2. Fill Slope Design

3. Cut Slope Design

Technical Memorandum Page 5

4. Fill Placement and Compaction Requirements

5. Ground Settlement

Site Preparation

At the on-set of earthwork, the area within the contract grading limits plus a minimum of 5 feet beyond the limits of grading should be cleared and grubbed thoroughly. Vegetation, debris, deleterious and other unsuitable materials should be removed and disposed of properly off-site.

Areas With 3 Feet or Less of Surface Volcanic Ash

In areas where 3 feet or less of surface volcanic ash is present below the pavement subgrades in cut areas or in areas designated to receive fills, the volcanic ash (or other soft, loose, weak, yielding areas, or cavities) should be over-excavated to expose basaltic rock, and the resulting excavation should be backfilled with well-compacted fills. Excavated volcanic ash, soft soils, and/or organic soils, if encountered, should be properly disposed of off-site, along fill slopes as discussed below, and/or used in landscape areas, where appropriate.

After removal of the surface volcanic ash, the over-excavated areas should be scarified to a depth of about 8 inches, where possible, moisture-conditioned to above the optimum moisture content, and recompacted to a minimum of 95 percent relative compaction prior to the backfilling operation. In the event that the natural basaltic rock formation is exposed at the subgrade elevation, the subgrade should be proof rolled with a minimum 20-ton vibratory drum roller (or a Caterpillar D-10 bulldozer) or similar heavy equipment for a minimum of eight passes. The vibratory drum roller should be operated at a speed of about 200 to 300 feet per minute. If the proof rolling operations detect near-surface cavities or loose zones in the subsurface, the area should be ripped open, cleaned of debris, and then backfilled with compacted fill materials. The proof-rolling operation also should be performed at the finished subgrades in cut areas.

Due to the potential for presence of cavities (lava tubes, blisters, pockets, etc.)

and soft and/or wet soils, we recommend including contingencies in the cost estimates for the project for over-excavation and structural fill placement to account for variations in the over-excavation and backfill quantities.

Areas With Greater Than 3 Feet of Surface Volcanic Ash

Because of the presence of relatively thick surface volcanic ash deposits (in excess of 15 feet), it is not economically practical to remove the ash deposits to expose the underlying firm material. Therefore, in areas with greater than 3 feet of surface volcanic ash below the pavement subgrades in cut areas or in areas designated to receive fills, a working platform as prescribed below should be

Technical Memorandum Page 6 established prior to filling or constructing the pavement section in these areas.

Due to the soft and weak nature of the volcanic ash, it is likely smaller sized construction equipment will be needed to install the working platform.

Fills greater than 42 inches

The working platform should consist of 42 inches of granular fill (6-inch minus granular fill). A layer of non-woven geotextile fabric such as Mirafi 180N or equal should overlay the volcanic ash deposits prior to placing the granular fill. The granular fill material should be placed in 12 to 18–inch maximum loose lifts and proof-rolled with a vibratory drum roller a minimum of four passes. The working platform should extend at least 5 feet beyond the toe of the fill slope or pavement section as shown on Plate 2.

Fills less than 42 inches and cuts

The working platform should consist of 30 inches of granular fill (6-inch minus granular fill) with two layers of geogrids to reinforce the working platform. A layer of woven geotextile fabric such as Mirafi 180N or equal and a layer of Tensar TX190L (or equivalent) geogrid should overlay the volcanic ash deposits, followed by 18 inches of granular fill (6-inch minus granular fill) reinforced with a second layer of Tensar TX190L (or equivalent) geogrid followed by 12 inches of granular fill (6-inch minus granular fill) for a total of 30 inches of working platform thickness. The granular fill material should be proof-rolled with a vibratory drum roller a minimum of four passes. The working platform should extend at least 5 feet beyond the toe of the fill slope as shown on Plate 2. A detail of the working platform in a cut condition is shown on Plate 3.

Fill Slope Design

Based on the subsurface conditions anticipated along the proposed alignment, we believe that the excavated materials, consisting mainly of basalt rocks and existing granular fill materials, may be re-used as a source of fill materials for embankment construction. However, volcanic ash soils generated from the cut areas should not be re-used as a source of general fill materials due to difficulties associated with obtaining proper compaction under the anticipated wet field conditions at the far eastern end of the alignment and the high natural moisture contents of the soils (in excess of 100 percent in many instances).

In general, we recommend that the fill areas of the project be capped with a minimum 2-foot thick layer of structural fill material to serve as a choking layer over the larger-sized general fill materials. Fill and backfill materials below the minimum 2-foot thick structural fill layer may consist of general fill materials. General fill and backfill

Technical Memorandum Page 7 materials should consist of well-graded granular materials, the majority of which are less than 12 inches in size with an absolute maximum dimension of 24 inches. The excavated on site materials, if less than 24 inches in maximum dimension, may be used as a source of general fill or backfill materials (other than for trench backfill), provided that they are processed to meet the above gradation requirements. If the excavated materials do not contain sufficient fines to produce a well-graded material, off-site borrow or on-site rock crushing of larger rock fragments or boulders should be considered to provide the required gradation and particle sizes to develop a well graded material.

Over-sized rock fragments may be disposed of off-site, used in deeper fills, or broken down to smaller-sized materials and incorporated into the fill material. The excavated on-site materials consisting of boulders less than 4 feet in diameter (but larger than 24 inches in largest dimension) may be used as rock fill provided that the top of the rock fill layer is placed at least 4 feet below the finished subgrades. In general, placement of boulders in fills should be in accordance with the procedures recommended in the "Boulder Disposal" subsection.

Due to the large extent of earthwork for this project, consideration should be given to mobilizing a crusher to the site to aid in reducing the size of large size boulders and excavated rock fragments. It is possible that portions of the dense basalt rock could yield material with characteristics suitable to allow its use as aggregate for construction purposes, such as aggregate subbase materials, if properly crushed and processed. A typical sketch of the recommended grading detail is shown on Plate 4 for reference.

If imported material to be used as select granular fill is needed, it should be non-expansive granular material, such as crushed coral, mudrock, or basalt. The select granular fill should be well graded from coarse to fine with particles no larger than 3 inches in largest dimension. The material should also contain less than 15 percent particles passing the No. 200 sieve. The material should have a laboratory CBR value of 25 or more and should have a maximum swell value of one percent or less. Imported fill materials should be tested for conformance with these recommendations prior to delivery to the project site for the intended use.

Permanent embankments constructed of the compacted on-site soils or imported fill material placed over competent ground such as basaltic rock should be designed with a slope inclination of 2H:1V or flatter. Permanent embankments constructed on working platforms overlying volcanic ash should be designed with a slope inclination of 2H:1V or flatter. Due to the soft and yielding nature of the volcanic ash, new fills should be placed in relatively thin level lifts at slow filling rates to reduce the potential for shear failure in the soft materials. The controlled rate of filling should be maintained to allow the consolidating soils to gain sufficient strength to support the next lift. The actual filling rate in the soft areas should be established in the field based on settlement gauge readings and adjusted to meet field conditions. Additionally, a settlement waiting period on the order of about 2 to 4 months will be required after completion of the fill

Technical Memorandum Page 8 embankment to the finished subgrade elevation before construction of other improvements, such as underground utilities and pavement structural sections, as described in the “Ground Settlement” section below.

Fills that are to be placed on slopes with inclinations steeper than 5H:1V should be keyed and benched into the existing slope to provide stability of the new fill against sliding. The filling operations should start at the lowest point and continue up in level horizontal compacted layers in accordance with the above fill placement recommendations. Fill slopes should be constructed by overfilling and cutting back to the design slope ratio to obtain a well-compacted slope face.

For fill slopes with a vertical height greater than 15 feet, we recommend that a key be provided at the toe of the fill slope to provide additional stability of the new fill embankment against sliding. The key should be embedded at least 2 feet below the lowest adjacent grade and should have a minimum base width of 10 feet.

Water should be diverted away from the tops of fill slopes, and slope planting should be provided as soon as the final slope is completed to reduce the potential for significant erosion of the finished slopes. Construction of earth berms, V-ditches, and the use of geotextile fabrics over the fill slope face should be considered to reduce the potential for significant erosion, thus enhancing the long-term stability of the planned fill slopes.

Additionally, we understand that surplus excavated volcanic ash material may be placed on fill slopes to dispose of the material on the project site. This type of fill slope with volcanic ash disposal should be designed with a slope inclination of 5H:1V or flatter.

Boulder Disposal

Over-sized materials, such as boulders, i.e., rock fragments larger than 24 inches in maximum size but less than 4 feet in largest dimension, encountered during site grading, may be used in rock fills provided that the following recommendations are followed:

1. Boulders less than 4 feet in largest dimension (but greater than 24 inches in largest dimension) may be utilized as rock fills, provided that the top of the boulder is placed at least 4 feet below the finished subgrades.

Boulders or portions of boulders should not encroach within 4 feet of the finished subgrade elevation. Boulders larger than 4 feet in maximum dimension should not be used as rock fill unless reduced in size.

2. Boulders greater than 24 inches in largest dimension should not be exposed at the face of the fill slope. Boulder placement should be setback

Technical Memorandum Page 9 a lateral distance of at least 6 feet measured from the edge of the fill slope face.

3. If underground utilities are planned (and known), care should be exercised to avoid placement of boulders in the proposed utility line alignment and within the depths of the proposed utility lines to reduce the potential for encountering the boulders during excavation for the utility line trenches.

Cut Slope Design

Based on the subsurface conditions anticipated along the proposed alignment, we believe the planned cut slopes may consist of materials ranging from volcanic ash to a'a and pahoehoe lava flows. In general, the a'a lava would consist of clinker materials with occasional layers of dense basalt; therefore, cut slopes exposing a’a lava should be designed in general accordance with the recommendations presented for “clinker” materials. On the other hand, pahoehoe lava flows generally consist of dense basalt with occasional clinker layers and, therefore, should be designed in general accordance with the recommendations presented for "dense basalt" materials. The following cut slope inclinations may be used for the design of the planned cut slopes along the proposed alignment.

GENERAL CUT SLOPE DESIGN RATIO

Type of Material Cut Slope Ratio

Volcanic Ash 3H:1V or Flatter

Clinker 1.5H:1V or Flatter

Dense Basalt 0.5H:1V or Flatter

Large cavities that may be exposed on the cut slope face should be backfilled and/or grouted, if necessary. In the event that over-cutting occurs (especially in basalt formation), consideration should be given to leaving the slope as-is rather than attempting to backfill the slope to the design grade with sliver fills. If backfilling of an over-cut slope is necessary, keying and benching requirements should be implemented.

Alternatively, cut slopes may be buttressed with fill slopes constructed of well compacted fills. However, the slope will need to be designed as a fill slope.

Water should be diverted away from the tops of cut slopes. Excessive surface water runoff over the slope face may cause erosion of the exposed soils, thus jeopardizing the long-term stability and performance of the cut slopes. Therefore, we believe cut slopes should be protected by appropriate slope planting or by other means, such as placement of geotextile fabrics on the slope face, as soon as practical after the slope is excavated to reduce the potential for significant erosion of the exposed soils. In

Technical Memorandum Page 10 addition, V-ditches may be considered at the top and bottom of the cut slopes to provide proper drainage of surface water runoff.

Excavation

Our field reconnaissance and exploration program disclosed that the majority of the proposed alignment generally is underlain by basalt rock formation consisting of a’a and pahoehoe type lava flows. It is anticipated that the basalt rock formation may be excavated with normal heavy excavation equipment, such as ripping with large bulldozers, where the rock is near the existing ground surface. However, excavations into the deeper formations may require the use of hoerams, chipping, or blasting. The method and equipment to be used for excavation should be determined by the contractor, subject to practical limits and safety considerations.

The above discussions regarding the rippability of the surface materials are based on our experience on the Island of Hawaii and the field exploration program performed at the project site. We recommend contractors proposing to bid on this project be encouraged to examine the site conditions and the boring data to make their own reasonable and prudent interpretation.

Fill Placement and Compaction Requirements

In general, fills and backfills should be moisture-conditioned to above the optimum moisture content, placed in level lifts not exceeding 8 inches in loose thickness, and compacted to at least 90 percent relative compaction. Fills and backfills within 3 feet of the pavement grade elevation should be compacted to a minimum of 95 percent relative compaction. Relative compaction refers to the in place dry density of soil expressed as a percentage of the maximum dry density of the same soil determined in accordance with AASHTO T-180. Optimum moisture is the water content (percentage by dry weight) corresponding to the maximum dry density. Compaction should be accomplished by sheepsfoot rollers, vibratory rollers, or other types of acceptable compaction equipment. Water tamping, jetting, or ponding should not be allowed to compact the fills.

Structural fill materials, consisting of granular fill materials with a maximum particle size of 6 inches, should be placed in level lifts not exceeding 12 inches in loose thickness, moisture-conditioned to above the optimum moisture, and compacted to at least 95 percent relative compaction. General fills and backfills should be placed in level lifts not exceeding 12 inches in loose thickness or the largest dimension of the majority of the materials, moisture conditioned to above the optimum moisture content, and compacted to a minimum of 90 percent relative compaction. Relative compaction refers to the in place dry density of soil expressed as a percentage of the maximum dry density of the same soil determined in accordance with AASHTO T-180. Optimum moisture is the water content (percentage by dry weight) corresponding to the maximum

Technical Memorandum Page 11 dry density. Compaction of fill materials should be accomplished using sheepsfoot rollers, vibratory rollers, or other types of acceptable compaction equipment.

"Rock" fills should be placed in lifts not exceeding the maximum dimension of the majority of the rocks or 5 feet, whichever is less. Placement should be by haul trucks traversing previously placed lifts and placing at the edge of the currently placed lift.

Spreading of the "rock" fill should be performed using a large bulldozer to facilitate "seating" of the rocks. The rock fill should be watered heavily during placement by water trucks traversing the front of the current rock lift face and spraying water continuously during placement.

Compaction equipment (such as a Caterpillar D-9 bulldozer or similar heavy compaction equipment) providing suitable energy to achieve the required compaction should be utilized to place rock fills. The number of passes (usually six to eight passes) to be made to achieve proper compaction should be determined at the on-set of site grading by the performance of a trial compaction test and/or by plate bearing tests.

Subsequent layers of rock fill above the previously placed rock fill should provide a choking layer of smaller sized boulder materials to fill in the voids between the boulders of the preceding rock fill layer.

Conventional compaction testing (field density testing) generally is not practicable in fills composed of rocks, boulders, and/or cobbles. Instead, a testing program to evaluate the number of passes by a compactor needed to achieve the desired level of compaction should be conducted at the start of the grading phase of the project under the observation of a Geolabs representative. Based on this testing program, the number of passes may then be used as the field criterion for adequate compaction. For preliminary estimating purposes, compaction may be accomplished by using a large vibratory drum roller having a static weight of at least 20 tons traveling at a speed of about 200 to 300 feet per minute. The roller should pass over the fill surface at least eight times for structural fill and six times for general fill. For general fill (with larger particle sizes), a Caterpillar D 9 bulldozer or similar size equipment may be used in-lieu of the vibratory drum roller.

It should be noted that it may not be possible to reduce the natural moisture content of the on-site volcanic ash soils to achieve the minimum 90 percent compaction criteria. In this case, we recommend compacting the volcanic ash to 100 percent of the dry density at the field moisture content. The wet method of sample preparation (HDOT TM 5-00) shall be used in determining the maximum dry unit weight. Increases in moisture due to rain or other external conditions or causes will not be acceptable reasons for using this method in determining relative compaction. Methods to compact the volcanic ash may include track rolling.

Technical Memorandum Page 12

Ground Settlement

Ground settlements are anticipated when new fills are placed over the existing ground to raise the site to the proposed finished elevations. Significant ground settlement likely will occur when new fills are placed over soft ground conditions.

In order to reduce the effects of the anticipated settlements on the pavements, structures, and other improvements constructed on the fills, implementation of a settlement waiting period will be necessary after placement of the fills and prior to construction of improvements on the fills.

Our preliminary analyses indicate that the settlement waiting period may range from a minimum of 2 months to about 4 months depending on the fill thickness, foundation soils, and implementation of soft soil stabilization measures. Because it is difficult to accurately predict the exact time required for the filled ground to settle, a settlement monitoring program using settlement gauges and settlement markers will be necessary. Therefore, provisions should be made for potential delays in the construction schedule where a settlement waiting period is required.

In order to reduce the waiting period, a temporary surcharge program may be considered for embankment fill over soft ground areas to accelerate the settlement process. Surcharge programs can aid in accelerating ground settlement, thus reducing the waiting period. It should be noted that some of the estimated ground settlements would occur as the fill loads are applied during the earthwork operations.

To monitor the actual settlement rate, we recommend installing settlement gauges and settlement markers in areas where fills are placed over soft soils.

Settlement gauges should be installed along soft soil areas prior to the fill placement operations. Settlement markers should be installed near the finished grades after completion of embankment construction.

In general, the gauges or markers should be read optically by a qualified professional surveyor, and the readings should be transmitted for review in a timely manner. We recommend taking two readings (minimum 24 hours apart) for each settlement gauge 10 days prior to any site filling to establish a baseline. Subsequent readings of the settlement gauges and settlement markers should be taken on a weekly basis for the entire filling and settlement waiting period.

Box Culverts & Pipe Culverts

Based on the current design concepts, we understand that eleven culverts will be constructed along the project alignment. These eleven culverts include six concrete box culverts and five pipe culverts. The following table summarizes the various culvert information.

Technical Memorandum Page 13

SUMMARY OF CULVERTS

Culvert No. Station Type Size (Total No.)

1 1743+35 Box 7' × 5' (5)

2 1771+25 Box 7' × 6' (5)

3 1776+43 Box 6' × 4' (2)

4 1794+69 Box 6' × 4' (2)

5 1811+28 Box 8' × 7' (1)

6 1819+00 Pipe 48" Dia. (1)

7 1829+00 Pipe 54" Dia. (1)

8 1841+62 Pipe 48" Dia. (1)

9 1847+25 Box 8' × 6' (2)

10 1849+98 Pipe 60" Dia. (1)

Relief 1 1734+70 Pipe 24" Dia. (1)

Based on the subsurface conditions encountered in our field exploration, we anticipate most of the new culverts will be situated over soft volcanic ash materials based on the locations provided. As noted above, the volcanic ash materials are soft and are susceptible to appreciable settlements when loaded by the weight of the backfill on the sides and above the box and pipe culverts. Therefore, the soft volcanic ash soils below the culvert structures should be over-excavated as discussed in further detail below.

The concrete box culvert structures and the associated headwall and wingwall structures and the pipe culvert headwall and wing wall structures should be designed to resist lateral and vertical earth pressures acting on them. Items that are addressed in the following subsections include:

Foundations Lateral Earth Pressures Backfill Drainage

Foundations

Soft volcanic ash materials are anticipated at the bottom of the new culvert structures. In order to provide adequate support to the new culverts and subsequent embankment fill over the culverts, over-excavation to remove the volcanic ash materials and expose the underlying dense materials followed by backfilling with select granular materials to the design invert elevations will be required for uniform bearing support.

Technical Memorandum Page 14

Based on the field exploration results adjacent to the new culvert structures, we expect the over-excavation will range up to about 14 feet beneath the existing ground surface at various locations. The following table summarizes the anticipated over-excavation depth at each culvert location.

SUMMARY OF OVER-EXCAVATION DEPTH ESTIMATIONS

Culvert No.

Station Reference Boring No.

Depth Beneath Culvert

Depth Beneath Existing Ground

(feet) (feet)

1 1743+35 B-232 3 8

2 1771+25 B-235 10 12

3 1776+43 B-236 10 11

4 1794+69 B-239 None None

5 1811+28 B-242 11 13

6 1819+00 B-242 14 13

7 1829+00 B-244 16 14

8 1841+62 B-246 8 8

9 1847+25 B-247 17 7

10 1849+98 B-247 11 7

Relief 1 1734+70 B-231 4 1

The over-excavation depths were estimated based on the borings drilled nearby the structures. The actual over-excavation limits should be evaluated in the field during construction. Therefore, contract documents should include additive and deductive unit prices for over excavating the soft soils and backfilling with compacted fill to account for variations in the over-excavation and backfill quantities.

In general, the over-excavation should be backfilled with select granular fill. An allowable bearing pressure of up to 5,000 pounds per square foot (psf) may be used to design the culvert and wall foundations (strength limit state) bearing on the properly compacted select granular fill. This bearing value provided is for supporting dead-plus-live loads and may be increased by 50 percent for transient loads, such as those caused by seismic forces (extreme event limit state).

Fills and backfills should be moisture-conditioned to above the optimum moisture, placed in level lifts not exceeding 12 inches in loose thickness, and compacted to at least 90 percent relative compaction. Fills and backfills within 3 feet of the pavement grade elevation should be compacted to a minimum of 95 percent relative compaction. Compaction should be accomplished by using sheepsfoot rollers, vibratory

Technical Memorandum Page 15 rollers, multiple-wheel pneumatic-tired rollers, or other types of acceptable compaction equipment.

We estimate that foundation settlements bearing on the select granular fill materials as recommended herein to be on the order of 1 to 1.5 inches.

Lateral loads acting on the structures may be resisted by friction developed between the bottom of the foundation and the bearing soil and by passive earth pressure acting against the near-vertical faces of the foundation system. A coefficient of friction of 0.78 and 0.62 may be used for the foundations bearing on the properly compacted select granular soils for the extreme event and strength limit states, respectively. Resistance due to passive earth pressure may be estimated using an equivalent fluid pressure of 350 and 175 pounds per square foot per foot of depth (pcf) for the extreme event and strength limit states, respectively.

Static Lateral Earth Pressures

The concrete box culvert and pipe culverts should be designed to resist the lateral earth pressure due to adjacent soil and surcharge effects. In general, an at-rest condition should be used for the box culvert because the walls are not free to deflect or are restrained. An active condition may be used for the wing walls that are free to deflect (cantilever) by as much as 0.5 percent of the wall height. The recommended lateral earth pressures for design of retaining structures, expressed in equivalent fluid pressures of pounds per square foot per foot of depth (pcf), are presented in the following table.

The values provided below assume that granular soils will be used to backfill behind the retaining structures. It is assumed that the backfill behind retaining structures will be compacted to between 90 and 95 percent relative compaction. However, over-compaction of the retaining structure backfill should be avoided. Compaction should be accomplished by suitable compaction equipment.

LATERAL EARTH PRESSURES

FOR DESIGN CULVERT STRUCTURES

Backfill Condition

Active (pcf)

At-Rest (pcf)

Level Backfill Above Water

34 54

Level Backfill Below Water

80 92

Surcharge stresses due to areal surcharges, line loads, and point loads within a horizontal distance equal to the depth of the retaining structures should be considered in the design. For uniform surcharge stresses imposed on the loaded side of the

Technical Memorandum Page 16 structure, a rectangular distribution with uniform pressure equal to 24 percent of the vertical surcharge pressure acting on the entire height of the wall, which is free to deflect (cantilever), may be used in design. For retaining structures that are restrained, a rectangular distribution equal to 39 percent of the vertical surcharge pressure acting over the entire height of the structures may be used for design. Additional analyses during design may be needed to evaluate the surcharge effects of point loads and line loads.

Dynamic Lateral Earth Pressures

Dynamic lateral earth forces due to seismic loading will need to be considered in the design of the box culvert, headwall, and wing wall retaining structures based on LRFD design methods. An appropriately reduced factor of safety (or resistance factor) may be used when dynamic lateral earth forces are accounted for in the design of retaining structures. Seismic loading (PGA or amax= 0.67g) is used to estimate the dynamic lateral earth pressures based on a peak bedrock acceleration (PBA) of 0.67g.

The table below summarizes the dynamic lateral earth forces acting on the retaining structure in the event of an earthquake versus the estimated wall displacements.

DYNAMIC LATERAL EARTH FORCES

FOR RETAINING STRUCTURES

Lateral Movement (inches)

Dynamic Lateral Earth Forces (H2 pounds per linear foot)

2.5 120

3.0 84

4.0 52

5.0 34

6.0 23

Please note that the above table only applies to level backfill conditions, where H is the height of the wall in feet. The resultant force should be assumed to act through the mid-height of the wall. The above dynamic lateral earth forces are in addition to the static lateral earth pressures provided above.

Backfill

The backfill around the culvert structures (within a minimum of 3 feet beyond the box culvert and wing wall structures) should consist of select granular fill (3-inch minus granular fill). Select granular fill should consist of non-expansive granular material, such as crushed coral, basalt or cinder sand. The material should be well-graded from coarse to fine with no particles larger than 3 inches in largest dimension and should contain less than 15 percent particles passing the No. 200 sieve. The material should have a

Technical Memorandum Page 17 laboratory CBR value of 20 or more and should have a maximum swell of less than 1 percent when tested in accordance with AASHTO T-193 (ASTM D1883).

Drainage

The headwall structures should be well drained to reduce the build-up of hydrostatic pressures. A typical drainage system should consist of open-graded gravel, such as AASHTO M 43, No. 67 gradation material, placed near the bottom and along the length of the wall discharging to an appropriate outlet or weep holes. As an alternative, the drainage system may consist of about 1 cubic foot of permeable material, such as AASHTO M 43, No. 67 gradation material, wrapped with non-woven, filter fabric at each of the weep hole locations. The weep holes should be spaced not more than 8 feet apart.

Closure

If you have questions or need additional information, please contact our office.

Attachments: Summary of Volcanic Ash Deposits, Plate 1 Working Platform - Fill Condition, Plate 2 Working Platform – Cut Condition, Plate 3 Typical Grading Detail, Plate 4

PLATES

B-201 1560+25 0 HP-14 1757+00 2.3

B-202 1566+77 0 HP-15 1758+00 >3

B-203 1569+72 0 HP-16 1759+00 2.8

B-204 1573+23 0 HP-17 1760+00 2

B-205 1581+76 0 B-234 1761+24 2

B-206 1586+22 0 HP-18 1762+00 0.5

B-207 1590+17 0 HP-19 1763+00 1.5

B-208 1596+32 0 HP-20 1764+00 1

B-209 1598+24 0 HP-21 1765+00 2.5

B-210 1603+15 0 HP-22 1766+00 1

B-211 1608+72 0 HP-23 1767+00 0.5

B-212 1614+17 0 HP-24 1768+00 0.25

B-213 1619+78 0 HP-25 1770+00 1

B-214 1627+75 0 HP-26 1771+00 0.5

B-215 1630+24 0 B-235 1771+50 2

B-216 1638+72 0 HP-27 1772+00 >3

B-217 1646+29 0 B-236 1776+24 11 B-218 1653+73 0 B-237 1778+22 0 B-219 1656+71 0 B-238 1787+22 0

B-220 1667+24 0 HP-28 1794+00 >3

B-221 1673+00 0 B-239 1794+76 2

B-222 1678+00 0 HP-29 1795+00 >3

B-223 1683+14 0 HP-30 1797+00 >3

B-224 1688+20 0 B-240 1799+37 12

B-225 1694+26 0 HP-31 1801+00 >3

B-226 1705+24 0 HP-32 1803+00 >3

B-227 1712+77 0 B-241 1804+35 13.5

B-228 1718+78 0 HP-33 1806+00 >3

B-229 1723+72 0 HP-34 1807+00 >3

B-230 1727+18 0 HP-35 1808+00 >3

B-231 1731+38 0 HP-36 1811+00 >3

B-232 1742+22 2 HP-37 1813+00 >3

HP-1 1743+00 3 B-242 1816+07 11.5

HP-2 1744+00 1.5 B-243 1821+04 9.5

HP-3 1745+00 2.5 B-244 1827+91 14

HP-4 1746+00 1 B-245 1837+82 9.5

HP-5 1747+00 2.8 B-246 1841+28 8.25

HP-6 1748+00 2.8 B-247 1847+26 7

HP-7 1749+00 2 HP-38 1848+50 >3

HP-8 1750+00 >3 HP-39 1850+00 2

HP-9 1751+00 2 HP-40 1850+50 >3

HP-10 1752+00 2.5 HP-41 1851+00 0.2

B-233 1753+26 2 HP-42 1851+50 >3

HP-11 1754+00 2.5 HP-43 1852+00 >3

HP-12 1755+00 >3 HP-44 1852+50 >3

HP-13 1756+00 1.5 HP-45 1854+00 0.5

APPROX.

STATION NO.

SURFACE ASH

THICKNESS

(feet)

SUMMARY OF SURFACE ASH DEPOSITS

HAWAII STATE ROUTE 200 (SADDLE ROAD)

MILEPOST 11 TO MILEPOST 5.6

(SADDLE ROAD EAST SIDE)

ISLAND OF HAWAII

APPROX.

STATION NO.

BORING /

PROBE NO.

SURFACE ASH

THICKNESS

(feet)

BORING /

PROBE NO.

W.O. 4984-40 GEOLABS, INC.

PLATE 1

JULY 2015

NOT TO SCALE

SADDLE ROAD EAST SIDE

HILO, HAWAII

MILE POST 5.6 TO MILE POST 11

DATE

SCALE

4984-40

DRAWN BY

JRP/ASP

W.O.

PLATE

EMBANKMENT FILL

SOFT SOIL/VOLCANIC ASH

NON-WOVEN GEOTEXTILE FABRIC

SOFT SOIL

30" MIN.

5' MIN.

SELECT TOPPING (6-INCH MINUS)

5' MIN.

GEOGRID

AUGUST 2015

NOT TO SCALE

SADDLE ROAD EAST SIDE

HILO, HAWAII

MILE POST 5.6 TO MILE POST 11

DATE

SCALE

4984-40

DRAWN BY

ASP

W.O.

PLATE

CAD User: ASPASIONJR File Last Updated: August 31, 2015 4:38:07pm Plot Date: August 31, 2015 - 4:42:42pm

File: T:\Drafting\Working\4984-40SaddleRoad\4984-40WorkingPlatform-CutCondition.dwg\CUT AREA

Plotter: DWG To PDF.pc3 Plotstyle: GEO-No-Dithering.ctb

LEGEND:

STRUCTURAL FILL

GENERAL FILL

2' MIN.

STRUCTURAL FILL

(6-INCH MINUS)

GENERAL FILL

PROOF-ROLLED SURFACE

UNYIELDING SURFACE

FINISHED

GRADEGREATER THAN 24"

WITHIN THIS ZONE)

4' MIN. (NO BOULDERS

6' SETBACK

JULY 2015

NOT TO SCALE

DATE

SCALE

4984-40

DRAWN BY

ASP

W.O.

PLATE

FACE AND WITHIN 4 FEET OF THE FINISHED SUBGRADE.

INTO A ZONE OF 6 FEET FROM THE FINISHED GRADE AT THE SLOPE

SEATED. BOULDERS (GREATER THAN 24") SHOULD NOT ENCROACH

FILLS PROVIDED THAT THEY ARE SPREAD OUT AND PROPERLY

BOULDERS (GREATER THAN 24") MAY BE DISPOSED OF IN GENERAL

NOTES:

File: 4984-40GradingDetail.dwg Jul 27, 2015 - 1:59pm

SADDLE ROAD EAST SIDE

HILO, HAWAII

MILE POST 5.6 TO MILE POST 11

TYPICAL GRADING DETAIL