008-GeotechnicalReport.pdf

Phone: (503) 656-0156 / fax: (503) 656-0186 / www.PacificGeotechnicalLLC.com

1419 Washington Street / Suite 101 / Oregon City, Oregon 97045

Geotechnical Engineering and Engineering Geology with a Focus on Sustainability

February 11, 2010

Cascade Design Professionals, Inc.

2780 SE Harrison Street, Suite 104 Milwaukie, Oregon 97222

Attention: Herb Fricke, PE

Subject: Report of Geotechnical Engineering Services Cape Perpetua Water & Wastewater Systems Lincoln County, Oregon

Project No: 1358-001-00

1. INTRODUCTION AND PROJECT UNDERSTANDING

Pacific Geotechnical, LLC (Pacific Geotechnical) is pleased to submit our report of geotechnical engineering services for the Cape Perpetua Water and Wastewater Systems project in Lincoln County, Oregon. Our work was completed in general accordance with our proposal dated January 27, 2010, which you authorized. The project is located south of Yachats as shown on Figure 1.

The project includes demolition of the existing wastewater system, construction of a new wastewater treatment plant, replacement of the potable water distribution system and improvements to the wellhead.

The existing wastewater system consists of a collection system, aeration lagoon and associated piping and systems. Portions of the system may remain with a new settling tank, recirculation tank, and associated filters, pumps and piping constructed. The new tanks are expected to be up to approximately 12,000 gallon buried tanks.

The new 2-inch diameter water supply line is expected to generally follow the existing water distribution system as shown on Figure 2. The water supply line will cross Highway 101 to access the Devil’s Churn Wayside. It is our understanding that the preferred option for this crossing is just south of the Cape Perpetua Campground entrance as shown on Figure 2.

Cape Perpetua Water & Wastewater Systems February 11, 2010

2. SCOPE OF SERVICES

The purpose of our services is to evaluate soil and groundwater conditions at the proposed crossing location and the water treatment plant location and provide our evaluation as to the suitability of the proposed work from a geotechnical standpoint. In addition, we completed surface observations of the remainder of the proposed alignment to provide our opinion of potential geotechnical issues noted at the surface. Our specific scope is provided in our proposal to you.

3. SITE CONDITIONS

3.1. GEOLOGIC AND SOIL MAPPING

The geology of the site is mapped in the Oregon Department of Geology and Mineral Industries (DOGAMI) Bulletin 81, Environmental Geology of Lincoln County, Oregon (Schlicker and others, 1973) and other references as noted below.

The subject site is located along the Oregon Coast south of the westernmost promontory of Cape Perpetua between that headland and the drainage of Cape Creek. The entire area is mapped as underlain by the Eocene-age Basalt of Yachats that forms the Cape Perpetua highland and underlies this section of the coast.

The soils at the site are mapped by the U.S. Department of Agriculture in the Soil Survey of Lincoln County Area (Shipman, 1997) as Neskowin-Salander silt loam, 35 to 65 percent slopes. These soils are reported as well drained, with moderate permeability, rapid runoff and high erosion hazard. Rapid erosion and soil loss are reported to be the principal hazard where vegetation is removed and the soil is not protected from runoff.

3.2. SURFACE CONDITIONS

The project site extends from the Devil’s Churn Wayside on the west side of Highway 101 south to the Cape Perpetua Visitor’s Center and east to the Cape Perpetua Campground. The primary focus for our work is the intersection of Highway 101 and the Cape Perpetua Campground entrance road, where the water line crossing is proposed, and the wastewater treatment plant, just southeast of the intersection.

Surface conditions at the proposed water line crossing location consist of a relatively flat grassy area on the east side of the highway just south of the campground entrance road, the two lane highway with a partial paved shoulder on the west side, and a relatively steep wooded slope descending to the ocean.

Basalt bedrock is exposed at the surface on the north side of the campground entrance road and extends along the east side of the highway. Based on a utility locate completed for our exploration work, power, telecommunication and the existing water supply line are located within the grassy area and extend under the highway near the intersection.

The existing waste water treatment plant is located east of Highway 101 and down a relatively steep slope south of the Cape Perpetua Campground entrance road. The treatment plant is located in a relatively flat fenced area surrounded by trees and brush. This area is accessible by a gravel road. A map of the existing site layout along with the location of the proposed improvements is provided as Figure 2.

File No. 1358-001-00

3.3. SUBSURFACE CONDITIONS

We explored subsurface soil and groundwater conditions at the site by digging two test pits to depths of between 6 and 10 feet below the ground surface (bgs) on January 29, 2010. We also used hand equipment to assess the shallow subsurface conditions to depths of approximately 3 feet bgs on the west side of Highway 101, in areas inaccessible to the backhoe. The exploration locations are shown on Figure 2.

Appendix A summarizes our exploration methods and presents our exploration logs. Laboratory test results are provided on the exploration logs or in Appendix B. The following paragraphs summarize the geologic units encountered in our explorations.

3.3.1. Fill (Unit Qaf)

Soils that we interpret as fill probably derived from nearby roadcuts in the native basalt and colluvial soil slopes were encountered from the ground surface to approximately 6 feet bgs in TP-2. This fill generally consisted of loose to medium dense silty sand and gravel, including large angular basalt fragments.

Measured moisture contents ranged between 11 and 26 percent, based on three tests. A fines content (passing #200 sieve) test measured 14 percent silt and clay particles at a depth of 4 feet bgs in this material.

In addition to the 6 feet of fill encountered in TP-2 we penetrated between 2½ to 3 feet of gravelly fill at several locations on the west side of Highway 101 at the locations shown on Figure 2.

Soils exposed at the ground surface suggest that much of the alignment along Highway 101 from Devil’s Churn to the intersection with the campground road, and along the campground road to the eastern terminus of the project is mantled with this fill, or colluvial soils similar in composition.

3.3.2. Alluvium (Unit Qal)

Soils encountered from the ground surface to the maximum depth explored in TP-1 generally consisted of silty sand/sandy silt with gravel to silty and clayey gravel soils we interpret as the native Cape Creek alluvium. This unit is not mapped by Schlicker and others (1973) but is mentioned in the bulletin text as commonly encountered mantling the older materials to shallow depths. This soil is generally medium stiff/dense below the topsoil zone, becoming dense at 8 feet bgs. Measured moisture contents ranged between 21 and 49 percent based on five tests. A single fines content test measured 21 percent silt and clay.

Our visual reconnaissance suggests that this soil is limited to the lowermost portions of the Cape Creek drainage.

3.3.3. Basalt of Yachats (Unit Teyb)

Dense basalt was encountered below 6 feet bgs in TP-2. It consists of basalt boulders or basalt blocks weathered from the top of the bedrock surface, and the backhoe was unable to excavate this basalt using maximum effort. The basalt is also exposed in several roadcuts, including directly east of the Devil’s Churn pullout, from about 40 feet north of the intersection of Highway 101 and the campground access road south to that intersection, and from Highway 101 almost 100 feet east along the north side of Cummins Peak Road. The basalt ranges from dark red-brown to gray where fresh and from highly fractured to massive (fracture spacing greater than several feet). Mapping suggests that this material underlies the entire region to hundreds of feet.

3.3.4. Groundwater

Groundwater was not encountered in any of our explorations at the time of our field investigation.

Observation and soil coloration suggest that the portions of the pipeline alignment from Devil’s Churn to the intersection of the campground road and the treatment plant road are above the water table in all but the wettest portions of the year. Within the campground the groundwater level is likely tied to the level of Cape Creek, suggesting that creek highstands may result in saturation of the low-lying areas around the treatment plant during part of the year. The groundwater conditions can change, however, due to changes in use, grading, seasonal precipitation and other factors.

3.4. GEOLOGIC HAZARDS

Schlicker and others (1973) maps geologic hazards for this portion of the coast. This mapping shows that the slopes around the Cape Creek drainage range from 25 to 50 percent, which corresponds with our observations. However, the hazards map does not show any landslides or topographic features indicative of landsliding and we did not observe indications of recent or active landsliding.

This portion of the coast is mapped as an area of “non-critical” coastline retreat, indicating that the risk to features nearby the active strandline such as Highway 101 are not immediately threatened by coastal bluff undermining and failure.

We did not observe other significant geologic hazards or active soil erosion on the site during our field investigation.

4. CONCLUSIONS

The following provide general conclusions related to the proposed project. These are discussed in more detail later in the text.

• The proposed pipeline crossing can likely be completed utilizing trenchless methods. Occasional cobbles, shallow bedrock, existing utilities, variable roadway embankment fill and limited access to the exit pit location should be considered during design and construction.

• Based on the observed subsurface and site conditions, horizontal directional drilling (HDD) will likely be the most economical trenchless technology method. Alternative methods including a jack and bore casing or pipe ramming may also be suitable.

• The existing wastewater treatment area is suitable for the proposed new facility although wet weather construction techniques will likely be required during most of the year.

While our scope did not include a detailed investigation of the remainder of the pipeline alignment, based on our visual observations, the following should be considered during construction:

• We observed occasional exposed boulders along the pipeline alignment through the campground.

Occasional boulders should be expected during trenching.

• The site slopes on the west side of Highway 101 are steep and wooded and will provide for difficult construction conditions if the waterline is constructed outside the guardrail. Ditches excavated in this slope should be properly shored and backfilled with structural fill.

• Bedrock is exposed at several locations near the pipeline alignment and may be encountered within the expected depth of excavation.

5. RECOMMENDATIONS

5.1. HIGHWAY 101 CROSSING

Due to the cost and inconvenience associated with an open trench excavation across Highway 101, trenchless methods are preferred. Based on our evaluation, a horizontal directional drill (HDD) across the road is the most suitable option. Other methods including pipe jacking or pipe ramming would also likely work, but would result in more set-up time, higher costs, and potentially higher risk from variable subsurface conditions.

5.1.1. General

HDD uses a drill rig that advances a piloted drill string from a boring pit or pad along a planned drill path to a receiving pit or pad. Drilling fluid, commonly called drilling mud, is circulated through the drill string to help convey drill cuttings away from the cutting bit as the drill head is advanced. The density and surface coating characteristics of the mud help maintain drill hole stability and keep the drill hole walls from collapsing. The drilling mud also reduces the movement of groundwater into the drilled hole. Once the drill string has reached the receiving pit, the bit is detached and the hole is reamed (if necessary) and the product pipe is pulled back through while drilling fluid is pumped down the hole.

5.1.2. Subsurface Constraints

Based on our limited explorations, constraints for the proposed HDD across Highway 101 include the following:

• potential cobbles and/or boulders,

• shallow bedrock,

• variable roadway embankment fill,

• existing utilities,

• difficult access to the HDD receiving pit, and

• the potential for mud loss including the potential to undermine the highway.

With the exception of the last two bullets, the above constraints can likely be dealt with by properly locating the HDD crossing and adjusting the drill string trajectory in the event that difficult drilling or impenetrable objects are encountered.

We recommend that the HDD receiving pit be excavated into the shoulder on the west side of the highway, rather than exiting directly onto the embankment slope. This will allow better equipment access and provide a pit to contain any drilling fluids. We recommend that the pit be kept to the minimum size practical and that the excavation be shored to prevent undermining of the adjacent roadway. Wood lagging, or similar material, may be used where the HDD bit is expected to exit, to allow penetration of the HDD bit while containing the surrounding soil.

All trench excavations should be made in accordance with applicable Occupational Safety and Health Administration (OSHA) and state regulations. Shoring at the receiving pit and near the highway should be properly designed by a registered professional engineer to ensure stability of the embankment and road prism. Elsewhere, shoring deeper than 6 feet should also be designed by a registered engineer. The shoring design engineer should be provided with a copy of this report. While this report describes certain approaches to excavation and shoring, the contractor is responsible for selecting and designing the specific methods, monitoring the excavations for safety, and providing shoring required to protect personnel, adjacent structural elements, and the roadway.

We recommend that Pacific Geotechnical be retained to observe the excavation for the receiving pit and provide additional recommendations if necessary. The HDD contractor should be provided with a copy of our report and complete additional potholing if they deem necessary.

5.1.3. Mud Loss

Drill mud is delivered to the cutting bit of the drill string under pressure. The mud leaves the cutting bit and flushes drill cuttings back along the drill path to the location of the drill rig, where it is circulated through a pit or mud tank and then reused in the drill hole. Soil formations around the drill path experience maximum mud pressures in the immediate proximity of the cutting bit.

Drilling mud can be lost in a directional drill hole by two processes:

• Formational mud loss: mud flows into surrounding permeable soil units within the pore spaces of the soil.

• Hydrofracturing: overburden soil can be over-pressurized, leading to physical displacement of the surrounding soil mass and mud loss along the resultant failure surfaces.

Both of these processes can result in loss of mud recirculation pressure and mud emergence at the ground surface. However, hydrofracturing is typically the process that is of greatest concern and has the potential for releasing relatively large volumes of drilling mud in a short time. The potential for hydrofracturing increases if the mud pressure is significantly greater than the overburden pressure of the soil above the drill path or the internal shear strength of the soil. Greater depths of soil cover above the drill path and lower mud pressure decrease the potential for mud loss by hydrofracturing.

Normal Best Management Practices (BMPs) should be implemented to minimize the potential for off-site transport of sediments during construction and drilling. This will minimize potential adverse impacts to the surface water collection system and adjacent areas in the vicinity of the bore. Generalized BMPs that may be utilized during drilling activities are discussed below.

Drilling fluids could potentially leak to the ground surface from soils near the drill entry and exit points.

Therefore, drilling fluid pressures should be limited to only that necessary to flush cuttings from the boring and maintain proper operation of the drilling equipment. The contractor should be prepared to monitor, respond and address fluid loss and containment should a leak occur. A contingency plan should be in place prior to commencing drilling operations that includes: 1) monitoring for drilling fluid pressure or volume loss; 2) visual monitoring for possible escape of drilling fluid; and 3) containment and mitigation in the event of fluid escape. Common BMPs used to decrease the potential for escape of drilling fluid via hydrofracture include:

• Reduce downhole drilling fluid pressures to the extent possible while maintaining adequate pressure for equipment operation.

• Continuously monitor drilling fluid pressures. Continuously monitor drilling fluid return volume.

• Visually monitor the ground surface during drilling. This will provide quick response in the event of fluid escape to the ground surface.

• Provide adequate containment of drilling fluids by properly sizing the return pond, employing containment structures (berms, etc.) and employing standard erosion control measures such as silt fencing and catch basin filters.

A careful evaluation should be completed to determine the location of all active and abandoned utilities in the vicinity of the bore path. If encountered, both active and abandoned utilities could provide a conduit for fluid loss.

We recommend that drilling operations be immediately halted if drilling fluid escapes to the surface. The drilling fluid should be contained using appropriate spill response equipment. Once contained, the drilling fluid should be reclaimed with a vacuum truck or other appropriate methods and disposed of appropriately.

5.1.4. Excavation Backfill

The receiving pit should be backfilled with structural fill per Section 5.3.4.

5.2. WATER TREATMENT PLANT

5.2.1. Site Preparation

Initial site preparation and earthwork operations will include removing any existing structural elements within the footprint for proposed new structures and excavation for utilities, shallow foundations and tanks.

All existing utilities in the construction area should be identified prior to excavation. Live utility lines identified beneath proposed structures should be relocated. Abandoned utility lines beneath structural components should be completely removed or grouted full in order to minimize potential settlement of new structures. Soft or loose soil encountered in utility line excavations should be removed and replaced with structural fill where it is located within structural areas.

If site preparation activities cause excessive subgrade disturbance, replacement with structural fill might be necessary. Disturbance to a greater depth should be expected if site preparation and earthwork are conducted during periods of excessive wet weather when the moisture content of the surficial soil could exceed optimum. All excavations required to remove underground materials should be backfilled with structural fill as described later in this report.

5.2.2. Subgrade Preparation and Evaluation

After subgrade preparation activities are complete, the prepared subgrade should be evaluated to identify remaining soft, loose or unsuitable areas. This can be accomplished by proofrolling with a fully loaded dump truck or similar heavy rubber tired equipment or by observing excavation activity and probing with a steel foundation probe. The proofroll/probing should be conducted prior to placing any other fill. The proofroll/probing should be observed by a representative of Pacific Geotechnical who should evaluate the suitability of the subgrade and identify any areas of yielding that are indicative of soft or loose soil. If soft or loose zones are identified during proofroll/probing, these areas should be excavated to the extent indicated by the engineer and replaced with structural fill.

5.2.3. Wet Weather Construction

The silty soils at the site can be expected to become disturbed during periods of wet weather or when the moisture content of the material is more than a few percentage points above optimum. This will likely be the case in all but mid-summer through early fall. When wet, the on-site silty soils are susceptible to disturbance and generally will provide inadequate support for construction equipment. If construction activities will occur during wet weather conditions, it may be necessary to use track-mounted equipment, loading removed material into trucks supported on granular haul roads or other methods to limit subgrade disturbance. The contractor should be responsible to protect the subgrade during construction.

5.2.4. Excavation

Site soils are generally expected to be medium dense to dense within expected excavation depths. It is our opinion that conventional earthmoving equipment in proper working condition should be capable of making necessary general excavations for the proposed structures in such soils. Rock may be encountered locally which is expected to be very hard. The rock may not be easily excavated with conventional equipment and hydraulic picks or other measures may be warranted. The earthwork contractor should be responsible to provide equipment and follow procedures as needed to excavate the site soils as described in this report.

5.2.5. Dewatering

Groundwater is not anticipated within the depths of expected excavation, except possibly at low points of the project site during highstands of Cape Creek. However, surface water inflow to the excavations during the wet season could be problematic. Provisions for temporary surface water control should be included in the project plans and should be installed prior to commencing work.

5.2.6. Shoring

Excavation sidewalls should stand near-vertical to a depth of at least 4 feet, provided perched or near-surface groundwater seepage does not affect the sidewalls. Excavations for the tanks or other structural elements should be laid back at the surface as necessary to prevent soil from falling into excavations. Excavations deeper than 4 feet should be shored or laid back at an inclination of 1.5 Horizontal to 1 Vertical (1.5H:1V) or flatter if workers are required to enter. All trench excavations should be made in accordance with applicable Occupational Safety and Health Administration (OSHA) and state regulations. Site soils are generally OSHA Type C.

If necessary, shoring should be completed as described in Section 5.1.2.

5.2.7. Excavation Backfill

The tank excavations should be backfilled with structural fill per Section 5.3.3 and 5.3.4.

5.2.8. Shallow Foundation Support Recommendations

5.2.8.1. General

When full, the settling tank and recirculation tank are expected to weigh less than or equal to the weight of the soil that will be excavated for these structures. Therefore, the underlying soils will not experience an increased load over existing conditions and settlement is not considered to be a significant design issue provided the subgrade is not disturbed from construction. The subgrade soils are not expected to rebound more than 1/2 inch as a result of decreased overburden pressure.

The proposed tanks and lightly loaded appurtenant structures can be supported on continuous wall or individual spread footings bearing on medium stiff/dense or better silt to silty sand and gravel or compacted structural fill. We recommend that continuous wall footings have a minimum width of 18 inches and individual spread footings have a minimum width of 24 inches.

5.2.8.2. Foundation Subgrade Preparation

We recommend that loose or disturbed soils be removed before placing reinforcing steel and concrete.

Compaction should be performed as described in Section 5.3.6 - Fill Placement and Compaction.

Foundation bearing surfaces should not be exposed to standing water. If water infiltrates and pools in the excavation, the water, along with any disturbed soil should be removed before placing reinforcing steel. A thin layer of crushed rock can be used to provide protection to the subgrade from weather and light foot traffic.

We recommend that Pacific Geotechnical observe all foundation excavations before placing concrete forms and reinforcing steel in order to determine that bearing surfaces have been adequately prepared and that the soil conditions are consistent with those observed during our explorations.

5.2.8.3. Bearing Capacity

We recommend that conventional wall and column foundations be proportioned using a maximum allowable bearing pressure of 2,500 pounds per square foot (psf). This bearing pressure applies to the total of dead and long-term live loads and may be increased by one-third when considering earthquake or wind loads. This is a net bearing pressure. The weight of the footing can be ignored in calculating footing sizes.

5.2.8.4. Foundation Settlement

Tank foundations are not expected to settle, as described above. Lightly loaded appurtenant structures designed and constructed as recommended are expected to experience settlements of less than 1 inch.

Differential settlements of up to one-half of the total settlement magnitude can be expected between adjacent footings supporting comparable loads.

5.2.8.5. Lateral Resistance

Lateral loads on footings can be resisted by passive earth pressures on the sides of footings and by friction on the bearing surface. We recommend that passive earth pressures be calculated using an equivalent unit weight of 250 pounds per cubic foot (pcf) for foundations confined by native medium stiff/dense or better silt to silty sand and gravel and 350 pcf if confined by a minimum of 2 feet of imported granular fill. We recommend using a friction coefficient of 0.35 for foundations placed on native medium stiff/dense or better silt to silty sand and gravel and 0.50 for foundations placed on a minimum 2-foot thickness of compacted crushed rock. The passive earth pressure and friction components may be combined provided that the passive component does not exceed two-thirds of the total.

The passive earth pressure value is based on the assumptions that the adjacent grade is level and that static groundwater remains below the base of the footing throughout the year. The top 1 foot of soil should be neglected when calculating passive lateral earth pressures unless the adjacent area is covered with pavement or is inside a building. The lateral resistance values do not include safety factors.

5.2.8.6. Pressure Relief Valves

Groundwater levels may rise above the floor level of the tanks during some portions of the year. Uplift forces due to buoyancy may not be fully resisted through the dead weight of the structure and frictional resistance between the soil and structure walls, especially if the tanks are empty. If this is the case, we recommend, concrete dead-men anchors structurally connected to the tanks, one-way pressure relief valves, or other measures be used to prevent floating of the structures due to buoyant forces.

5.3. WATER LINE CONSTRUCTION

With the exception of the proposed highway crossing, our scope did not include subsurface investigations along the proposed water line. However, we completed a visual reconnaissance of the existing pipeline alignment and did not observe any significant damage due to slope failure, settlement or other related issues. The following sections provide general recommendations for pipeline construction.

5.3.1. Dewatering

See Section 5.2.5.

5.3.2. Shoring

If necessary, shoring should be completed as described in Section 5.1.2 above and to protect the Highway 101 road prism.

5.3.3. Trench/Tank Backfill

Backfill for pipe bedding and in the pipe zone and tank bedding should consist of well-graded granular material with a maximum particle size of ¾-inch and less than 5 percent passing the U.S. No. 200 Sieve.

The material should be free of organic matter and other deleterious materials. Further, the backfill should meet the pipe or tank manufacturer’s recommendations. Above the pipe zone and for tank backfill imported granular fill or crushed rock may be used as described below and that is compatible with the overlying use. The pipe backfill should be placed and compacted in lifts with maximum uncompacted thicknesses and relative densities as recommended in the tables that follow.

5.3.4. Imported Select Structural Fill

Select imported granular material may be used as structural fill. The imported material should consist of pit or quarry run rock, crushed rock or crushed gravel and sand that is fairly well graded between coarse and fine sizes. It should be free of debris, clay balls, roots, organic matter, frozen soil, man-made contaminants, and other deleterious materials. It should have a maximum particle size of 4 inches and less than 5 percent passing the U.S. No. 200 Sieve. During dry weather, the fines content can be increased to a maximum of 12 percent.

The material should be placed and compacted in lifts with maximum uncompacted thicknesses and relative densities as recommended in the tables that follow.

5.3.5. Aggregate Bases

Aggregate base rock located under pavements or crushed rock used in footing over excavations should consist of imported, clean, durable, crushed angular rock. Such rock should be well-graded, have a maximum particle size of 1-1/2 inch, and less than 5 percent passing the U.S. No. 200 Sieve. The material should be placed and compacted in lifts with maximum uncompacted thicknesses and relative densities as recommended in the tables that follow.

In addition, aggregate base located under pavements should conform to Section 02630 of the most current edition of the Standard Specifications for Highway Construction, Oregon Department of Transportation (ODOT) with the addition that the material meet the recommendations above and have at least two mechanically fractured faces.

5.3.6. Fill Placement and Compaction

Structural fill should be placed and compacted in accordance with the following:

• Place all fill and backfill on a prepared subgrade that consists of firm, inorganic native soils or approved structural fill.

• Place all fill or backfill in uniform horizontal lifts with a thickness appropriate for the material type and compaction equipment. The following table provides general guidance for lift thicknesses.

• Use appropriate operating procedures to attain uniform coverage of the area being compacted.

• Place fill at a moisture content within about 3 percent of optimum as determined in accordance with ASTM Test Method D1557. Moisture condition fill soil to achieve uniform moisture content within the specified range before compacting.

• Do not place, spread or compact fill soils during freezing or unfavorable weather conditions.

Frozen or disturbed lifts should be removed or properly recompacted prior to placement of subsequent lifts of fill soils.

Table 1. Guidelines for Uncompacted Lift Thickness

Guidelines for Uncompacted Lift Thickness (inches)

Compaction Equipment

Granular and Crushed Rock Maximum

Particle Size ≤ 1 1/2 inch

Crushed Rock Maximum Particle Size > 1 1/2 inch

Plate Compactors and Jumping Jacks 4 – 8 Not Recommended

Rubber-tire Equipment 10 – 12 6 – 8

Light Roller 10 – 12 8 – 10

Hoe Pack Equipment 18 – 24 12 – 16

Note:

The above table is based on our experience and is intended to serve as a guideline. The information provided in this table should not be included in the project specifications.

• Do not place fill and backfill until tests and evaluation of the underlying materials have been made and the appropriate approvals have been obtained.

• Do not damage or displace underground utilities or adjacent structures during backfilling and compaction.

• Grade the surface of the fill at the end of each working shift so that surface water can drain readily.

• Compact fill soils to the percentages of maximum dry density as shown in Table 2.

Table 2. Fill Compaction Criteria

Percent of Maximum Dry Density Determined in Accordance with ASTM D1557

Fill Type

0 – 2 Feet Below Subgrade

>2 Feet Below Subgrade

Pipe Bedding and Pipe Zone

Aggregate Bases1 95 95 ------

Trench Backfill 95 92 90 2

Nonstructural Trench Backfill 88 88 ------

Nonstructural Zones 88 88 90 2

Notes:

1 Structural fill with more than 30 percent retained on the ¾ inch sieve should be compacted to a well keyed dense state within 3 percent of optimum moisture content. Compaction should be verified by performance testing such as a proofroll.

2 Or per pipe manufacturers recommendations within pipe zone.

During structural fill placement and compaction, a sufficient number of in-place density tests should be completed by Pacific Geotechnical to verify that the specified degree of compaction is being achieved.

For structural fill with more than 30 percent retained on the ¾-inch sieve, Pacific Geotechnical should visually verify proper compaction with a proofroll or other methods.

6. CONSTRUCTION OBSERVATIONS

Satisfactory foundation and earthwork performance depends to a large degree on quality of construction.

Sufficient monitoring of the contractor’s activities is a key part of determining that the work is completed in accordance with the construction drawings and specifications. Subsurface conditions observed during construction should be compared with those encountered during the subsurface exploration. Recognition of changed conditions often requires experience; therefore, Pacific Geotechnical or their representative should visit the site with sufficient frequency to detect whether subsurface conditions change significantly from those anticipated.

We recommend that Pacific Geotechnical be retained to monitor construction at the site to confirm that subsurface conditions are consistent with the site explorations and to confirm that the intent of project plans and specifications relating to earthwork and foundation construction are being met. In particular, we recommend that foundation subgrades and compaction of structural backfill be observed and/or tested by Pacific Geotechnical. Further, we recommend that we be retained to monitor excavation of the receiving pit to confirm conditions are as anticipated.

7. LIMITATIONS

We have prepared this report for the exclusive use of Cascade Design Professionals, Inc. and their authorized agents for the Cape Perpetua Water and Wastewater System Improvements project in Lincoln County, Oregon in accordance with our Agreement for Professional Services. Our report is intended to provide our opinion of geotechnical parameters for design and construction of the proposed project based on exploration locations that are believed to be representative of site conditions. However, conditions can vary significantly between exploration locations and our conclusions should not be construed as a warranty or guarantee of subsurface conditions or future site performance.

Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in the field of geotechnical engineering in this area at the time this report was prepared. No warranty, express or implied, should be understood.

Any electronic form, facsimile or hard copy of the original document (email, text, table, and/or figure), if provided, and any attachments are only a copy of the original document. The original document is stored by Pacific Geotechnical and will serve as the official document of record.

8. REFERENCES

Occupational Safety and Health Administration (OSHA) Technical Manual Section V: Chapter 2, Excavations: Hazard Recognition in Trenching and Shoring, accessed December, 2008:

http://www.osha.gov/dts/osta/otm/otm_v/otm_v_2.html.

Oregon Department of Transporation (ODOT), 2008 Standard Specifications for Construction, 2008.

Schlicker, H.G., Deacon, R.J., Olcott, G.W., and Beaulieu, J.D, 1973. Environmental Geology of Lincoln County, Oregon. Oregon Department of Geology and Mineral Industries, Bulletin 81, 171 p, 6 plates, 1:63,600 scale.

Shipman, J.A., 1997, Soil Survey of Lincoln County Area, Oregon, U.S. Department of Agriculture Natural Resources Conservation Service, 158 p., accessed Fabruary, 2010 from USDA/NRCS website http://soildatamart.nrcs.usda.gov/manuscripts/OR638/0/or638_text.pdf

9. CLOSING

We appreciate the opportunity to submit this report to you. Please contact us if you have any questions or need additional information.

Sincerely, Greg A. Landau, PE Vice President

Attachments Document ID: 1358-001-00R.doc http://soildatamart.nrcs.usda.gov/manuscripts/OR638/0/or638_text.pdf Greg Oregon PE

APPENDIX A

FIELD EXPLORATIONS

APPENDIX A

FIELD EXPLORATIONS

We evaluated subsurface soil and groundwater conditions at the site by completing 2 test pit explorations, 3 hand auger/probe explorations, and performing a visual reconnaissance. The subsurface exploration locations were approximately located by pacing from existing site features and are shown in report Figure

2. Exploration locations should be considered accurate only to the degree implied by the methods used.

The test pits were excavated by Dan Fischer Excavating using a rubber-tired JD 310C backhoe. Grab samples were obtained from the explorations at the locations indicated on the test pit logs.

We used a 2.75 inch soil auger and a ¼-inch diameter steel rod probe to investigate shallow soil conditions in areas that were inaccessible to the backhoe.

Materials encountered in the explorations were classified in the field in general accordance with ASTM D2488, “Standard Practice for the Classification of Soils (Visual-Manual Procedure)”. Soil classifications and sampling intervals are shown on the exploration logs in this appendix.

The field explorations were coordinated by an engineering geologist from our staff, who located the test pits and employed the hand equipment, classified the various soil units encountered, obtained representative soil samples for geotechnical testing, observed and recorded groundwater conditions, and maintained a detailed log of each test pit and auger boring.

Results of the laboratory testing are indicated on the exploration logs and are included in Appendix B.

MATERIAL

TYPES MAJOR DIVISIONS

PT

GW

GP

GM

GC

SW

SP

SM

SC

CL

ML

OL

CH

MH

OH

GRAVELS

ORGANIC

INORGANIC

ORGANIC

F

IN

E -G

R A

IN

E

D S

O

IL

S

P A

S S

E S

N O

. 2

S

IE

V E

C O

A R

S E

-G R

A

IN

E D

S O

IL

S

R

E T

A

IN

E D

O N

N O

. 2

S

IE

V E

HIGHLY ORGANIC SOILS

SILTS AND CLAYS

LIQUID LIMIT<50

SILTS AND CLAYS

LIQUID LIMIT>50

PEAT

SANDS

INORGANIC

SANDS AND FINES

>12% FINES

CLEAN SANDS

<5% FINES

SOIL GROUP NAMES & LEGENDGROUP

SYMBOL

GRAVELS WITH

FINES, >12% FINES

ATT

CP

CA

CN

DD

DS

HA

OC

PP

P200

SA

SW

TV

UC

Atterberg Limits

Laboratory Compaction Test

Chemical Analysis (Corrosivity)

Consolidation

Dry Density

Direct Shear

Hydrometer Analysis

Organic Content

Pocket Penetrometer (TSF)

Percent Passing No. 200 Sieve

Sieve Analysis

Swell Test

Torvane Shear

Unconfined Compression

CLEAN GRAVELS

<5% FINES

WELL-GRADED GRAVEL

POORLY-GRADED GRAVEL

SILTY GRAVEL

CLAYEY GRAVEL

WELL-GRADED SAND

POORLY-GRADED SAND

SILTY SAND

CLAYEY SAND

LEAN CLAY

SILT

ORGANIC CLAY OR SILT

FAT CLAY

ELASTIC SILT

ORGANIC CLAY OR SILT

>50% OF COARSE

FRACTION PASSES

ON NO 4. SIEVE

>50% OF COARSE

FRACTION RETAINED

ON NO 4. SIEVE

Notes:

Blowcount (N) is recorded for driven samplers as the number of blows required to advance sampler 12 inches (or distance noted) per ASTM D-1586. See exploration log for hammer weight and drop.

(2.4-inch) sampler N approximately correlated to equivalent SPT N by 50% reduction in N - modified California.

Refer to the report text and exploration logs for a proper understanding of subsurface conditions. Descriptions on the logs apply only at the exploration locations at the time the explorations were made. The logs are not warranted to be representative of the subsurface conditoins at other locations or times.

Note: Multiple symbols are used to indicate borderline or dual classifications

SOIL CLASSIFICATION CHART

SEEPAGE MODIFIERS

GROUNDWATER SYMBOLSLABORATORY/ FIELD TESTS

KEY TO EXPLORATION LOGS

Pacific Geotechnical, LLC 1419 Washington Street, Suite 101 Oregon City, Oregon 97045

Concrete

OTHER MATERIAL

SYMBOLS

Asphalt

CAVING MODIFIERS MINOR CONSTITUENTSMOISTURE MODIFIERS

SAMPLE TYPES

Water Level (at time of drilling)

Water Level (at end of drilling)

Water Level (after drilling)

Topsoil

Dry

Moist

Wet

None

Slow

Moderate

Heavy isolated frequent general

Trace

Occasional

With

Absence of moisture, dusty, dry to the touch

Damp, but no visible water

Visible free water or saturated, usually soil is obtained from below the water table

< 1 gpm

1-3 gpm

> 3 gpm

None

Minor

Moderate

Severe

< 5% (silt/clay)

< 15% (sand/gravel)

5-15% (silt/clay) in sand or gravel

15-30% (sand/gravel) in silt or clay

Standard Penetration Test (SPT)

Shelby Tube

Bulk or Grab

Dames & Moore

STRATIGRAPHIC CONTACT

Distinct contact between soil strata or geologic units

Gradual or approximate change between soil strata or geologic units

K E

Y T

O E

X P

LO

R

A T

IO

N

L O

G S

G

IN

T

S T

D U

S L

A B

.G D

T

0/

6/

1:

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S \P

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4-

-F R

E D

M E

Y E

R

S A

N D

Y \G

IN

T

\S A

N D

Y L

O G

S .G

P J

GB

GB

GB

GB

GB

MC = 49%

MC = 44%

Fines = 21%

MC = 36%

MC = 21%

MC = 27%

ML-

SM

GM

5.5

10.0

(ML-SM) Dark brown SILT with sand and gravel to SILTY SAND with gravel, trace cobbles, some organic matter and duff (moist, medium stiff to stiff and medium dense) [Alluvium]

Grades to brown trace yellow decomposed sandstone gravels

(GM) grades to brown SILTY GRAVEL with medium to coarse SAND, trace cobbles (moist to wet, medium dense) grades to yellow-brown SILTY to CLAYEY GRAVEL with medium to coarse SAND, trace cobbles and red-brown mottling (wet, dense)

Test pit completed at 10 ft.

No groundwater encountered.

GROUND ELEVATION

LOGGED BY J. Lawes

EXCAVATION METHOD John Deere 310 C backhoe

EXCAVATION CONTRACTOR Dan Fischer Excavating GROUND WATER LEVELS:

CHECKED BY G. Landau

DATE STARTED 1/29/10 COMPLETED 1/29/10

AT TIME OF EXCAVATION ---

AT END OF EXCAVATION ---

AFTER EXCAVATION ---NOTE:

TEST PIT SIZE N/A

S A

M P

LE

T

Y P

E N

U M

B E

R

D E

P T

H (f t)

0.0

2.5

5.0

7.5

10.0

TEST PIT NUMBER TP-1

CLIENT Cascade Design Professionals, Inc.

PROJECT NUMBER 1358-001-00

PROJECT NAME Cape Perpetua Water & Wastewater Systems

PROJECT LOCATION Yachats, Oregon

G E

N E

R A

L B

H

T P

W

E

LL

G

IN

T

S T

D U

S L

A B

.G D

T

/1

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T

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8-

C A

P E

P E

R P

E T

U A

\G

IN

T \1

T

E S

T P

IT

L

O G

S .G

P J

Pacific Geotechnical 1419 Washington Street Oregon City, Oregon 97045 Telephone: 503-656-0156 Fax: 503-656-0186

R E

C O

V E

R Y

TESTS

U .S

.C .S

G R

A P

H

IC

LO

G

MATERIAL DESCRIPTION

GB

GB

GB

MC = 26%

MC = 16%

Fines = 14%

MC = 11%

SM

GM

1.0

6.0

(SM) Brown SILTY fine SAND, trace to some rounded and subangular basalt gravel, roots to 4" (moist, loose) [Fill]

6-inch thick layer of yellow SILTY coarse SAND (moist, loose)

(GM) Brown SILTY GRAVEL with medium SAND, angular basalt gravels, trace to some cobbles (moist, medium dense) grades to medium dense to dense, occasional increasing to frequent basalt boulders or bedrock

Practical refusal on basalt at 6 ft.

No groundwater encountered.

GROUND ELEVATION

LOGGED BY J. Lawes

EXCAVATION METHOD John Deere 310 C backhoe

EXCAVATION CONTRACTOR Dan Fischer Excavating GROUND WATER LEVELS:

CHECKED BY G. Landau

DATE STARTED 1/29/10 COMPLETED 1/29/10

AT TIME OF EXCAVATION ---

AT END OF EXCAVATION ---

AFTER EXCAVATION ---NOTE:

TEST PIT SIZE N/A

S A

M P

LE

T

Y P

E N

U M

B E

R

D E

P T

H (f t)

0.0

2.5

5.0

TEST PIT NUMBER TP-2

CLIENT Cascade Design Professionals, Inc.

PROJECT NUMBER 1358-001-00

PROJECT NAME Cape Perpetua Water & Wastewater Systems

PROJECT LOCATION Yachats, Oregon

G E

N E

R A

L B

H

T P

W

E

LL

G

IN

T

S T

D U

S L

A B

.G D

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C A

P E

P E

R P

E T

U A

\G

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T \1

T

E S

T P

IT

L

O G

S .G

P J

Pacific Geotechnical 1419 Washington Street Oregon City, Oregon 97045 Telephone: 503-656-0156 Fax: 503-656-0186

R E

C O

V E

R Y

TESTS

U .S

.C .S

G R

A P

H

IC

LO

GM

0.5

(GM) Brown SILTY GRAVEL with medium SAND, angular basalt gravel (moist, medium dense) [Fill]

Practical Refusal of Hand Auger at 0.5 ft.

No groundwater encountered

Foundation probe driven to maximum depth with moderate effort

GROUND ELEVATION

LOGGED BY J. Lawes

DRILLING METHOD Hand auger/steel probe

DRILLING CONTRACTOR N/A GROUND WATER LEVELS:

CHECKED BY G. Landau

DATE STARTED 1/29/10 COMPLETED 1/29/10

AT TIME OF DRILLING ---

AT END OF DRILLING ---

AFTER DRILLING ---NOTE:

HOLE SIZE N/A

S A

M P

LE

T

Y P

E N

U M

B E

R

D E

P T

H (f t)

0.0

2.5

BORING NUMBER HA/P-1

CLIENT Cascade Design Professionals, Inc.

PROJECT NUMBER 1358-001-00

PROJECT NAME Cape Perpetua Water & Wastewater Systems

PROJECT LOCATION Yachats, Oregon

G E

N E

R A

L B

H

T P

W

E

LL

G

IN

T

S T

D U

S L

A B

.G D

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P E

R P

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E S

T P

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O G

S .G

P J

Pacific Geotechnical 1419 Washington Street Oregon City, Oregon 97045 Telephone: 503-656-0156 Fax: 503-656-0186

U .S

.C .S

G R

A P

H

IC

LO

1.0

(GM) Dark brown SILTY GRAVEL with medium to coarse SAND, traces of asphalt (moist, medium dense) [Fill]

Practical Refusal of hand auger at 1 ft.

No groundwater encountered.

Foundation probe driven to 2.5 ft. with moderate to extreme effort

GROUND ELEVATION

LOGGED BY J. Lawes

DRILLING METHOD Hand auger/steel probe

DRILLING CONTRACTOR N/A GROUND WATER LEVELS:

CHECKED BY G. Landau

DATE STARTED 1/29/10 COMPLETED 1/29/10

AT TIME OF DRILLING ---

AT END OF DRILLING ---

AFTER DRILLING ---NOTE:

HOLE SIZE N/A

S A

M P

LE

T

Y P

E N

U M

B E

R

D E

P T

H (f t)

0.0

2.5

BORING NUMBER HA/P-2

CLIENT Cascade Design Professionals, Inc.

PROJECT NUMBER 1358-001-00

PROJECT NAME Cape Perpetua Water & Wastewater Systems

PROJECT LOCATION Yachats, Oregon

G E

N E

R A

L B

H

T P

W

E

LL

G

IN

T

S T

D U

S L

A B

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T

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0:

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R P

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\G

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E S

T P

IT

L

O G

S .G

P J

Pacific Geotechnical 1419 Washington Street Oregon City, Oregon 97045 Telephone: 503-656-0156 Fax: 503-656-0186

U .S

.C .S

G R

A P

H

IC

LO

0.5

(GM) Brown SILTY GRAVEL with medium to coarse SAND, angular basalt gravel (moist, medium dense) [Fill]

Practical Refusal of Hand Auger at 0.5 ft.

No groundwater encountered

Foundation probe driven to maximum depth with moderate effort

GROUND ELEVATION

LOGGED BY J. Lawes

DRILLING METHOD Hand auger/steel probe

DRILLING CONTRACTOR N/A GROUND WATER LEVELS:

CHECKED BY G. Landau

DATE STARTED 1/29/10 COMPLETED 1/29/10

AT TIME OF DRILLING ---

AT END OF DRILLING ---

AFTER DRILLING ---NOTE:

HOLE SIZE N/A

S A

M P

LE

T

Y P

E N

U M

B E

R

D E

P T

H (f t)

0.0

2.5

BORING NUMBER HA/P-3

CLIENT Cascade Design Professionals, Inc.

PROJECT NUMBER 1358-001-00

PROJECT NAME Cape Perpetua Water & Wastewater Systems

PROJECT LOCATION Yachats, Oregon

G E

N E

R A

L B

H

T P

W

E

LL

G

IN

T

S T

D U

S L

A B

.G D

T

/1

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0:

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R P

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T P

IT

L

O G

S .G

P J

Pacific Geotechnical 1419 Washington Street Oregon City, Oregon 97045 Telephone: 503-656-0156 Fax: 503-656-0186

U .S

.C .S

G R

A P

H

IC

LO

APPENDIX B

LABORATORY TESTING

APPENDIX B

LABORATORY TESTING

GENERAL

Soil samples obtained from the explorations were transported to our laboratory and evaluated to confirm or modify field classifications, as well as to evaluate engineering properties of the soils encountered.

Representative samples were selected for laboratory testing. The tests were performed in general accordance with the test methods of the American Society for Testing and Materials (ASTM) or other applicable procedures.

VISUAL CLASSIFICATIONS

Soil samples obtained from the explorations were visually classified in the field and in our geotechnical laboratory based on the Unified Soil Classification System (USCS) and ASTM classification methods.

ASTM Test Method D2488 was used to classify soils using visual and manual methods. ASTM Test Method D2487 was used to classify soils based on laboratory test results.

Moisture Content

Moisture contents of samples were obtained in general accordance with ASTM Test Method D2216. The results of the moisture content tests completed on samples from the explorations are presented on the exploration logs included in Appendix A.

Fines Content

Two fines content tests were completed in general accordance with ASTM Test Method D-1140. The results of the fines content tests are presented on the boring logs in Appendix A.