14May2012Geotechnical_ _Foundation_Report_-_Final.pdf

Kitchen Creek Helibase - CNF December 2011

Cleveland National Forest

Proposed Kitchen Creek Helibase Geotechnical Site Evaluation

Prepared by Michelle L. H. Bearmar, PE

SoCal Province Geotechnical Engineer For Tammie Mather, Project Engineer Cleveland National Forest, Region 5

1.0 BACKGROUND AND SCOPE

2.0 PROJECT DESCRIPTION

3.0 GEOTECHNICAL INVESTIGATION

3.1 FIELD EXPLORATIONS

3.2 PHYSICAL TESTING

4.0 SITE CHARACTERISTICS

4.1 GEOLOGY AND TOPOGRAPHY

4.1.1 Regional Geology

4.1.2 Local Geology & Topography

4.2 SOILS AND WATER

4.3 WIND, SNOW AND FROST

4.4 FAULTING

5.0 DISCUSSION OF FINDINGS

5.1 SUBSURFACE CONDITIONS

5.2 GROUNDWATER

5.3 SOIL PROPERTIES AND STRENGTH CHARACTERISTICS

5.4 PERCOLATION TEST

6.0 ENGINEERING SEISMOLOGY

6.1 IBC / NEHRP SEISMIC PARAMETERS FOR NEW BUILDINGS

6.2 LIQUEFACTION POTENTIAL

7.0 DESIGN RECOMMENDATIONS

7.1 SITE PREPARATION, EXCAVATION AND BACKFILL

7.2 FOUNDATION RECOMMENDATIONS

7.3 CONCRETE SLABS

7.4 PAVEMENT RECOMMENDATIONS

7.4.1 Design Parameters

7.4.2 Asphalt Pavement Sections

7.4.3 Portland Cement Concrete Pavement Sections

7.5 MISCELLANEOUS DESIGN PARAMETERS

8.0 POST INVESTIGATION/DESIGN REVIEW

9.0 CLOSURE

10.0 REFERENCES

11.0 APPENDICES

APPENDIX A - MAPS

A.1 LOCATION MAP

A.2 VICINITY MAP

A.3 PROJECT AREA MAP

A.4 AERIAL VIEWS

A.4.1 Project Vicinity A.4.2 Project Area A.4.3 Project Boundary

A.5 LOCAL GEOLOGY MAP

A.6 SITE PLAN

APPENDIX B – CONE PENETRATION TESTING

B.1 CPT LOCATIONS

B.2 CPT RESULTS

B.2.1 CPT-1

B.2.2 CPT-2

APPENDIX C – SEISMIC TESTING

C.1 SHEAR WAVE VELOCITY PROFILE

APPENDIX D – SOIL TESTING

D.1 SOIL TEST LOCATIONS

D.2 PLASTICITY AND CLASSIFICATION OF SURFICIAL SOILS

D.3 GRADATION

D.3.1 Building Pads Location D.3.2 Helipads Location

D.4 EXPANSION INDEX

D.4.1 Building Pads Location D.4.2 Helipads Location

D.5 EXPANSION INDEX

D.5.1 Building Pads Location D.5.2 Helipads Location

D.6 CALIFORNIA BEARING RATIO

D.6.1 Building Pads Location D.6.2 Helipads Location

D.7 R-VALUE

D.7.1 Building Pads Location D.7.2 Helipads Location

D.8 SUMMARY

APPENDIX E – FAULTING/SEISMIC

E.1 CGS FAULT MAP

E.2 USGS PROBABILISTIC SEISMIC HAZARD MAP

E.3 SITE SPECIFIC NEHRP SEISMIC PARAMETERS

APPENDIX F – BEARING CAPACITY GRAPHS

F.1 BUILDING PADS LOCATION

F.1.1 Continuous F.1.2 Rectangular Footings

F.2 HELIPADS LOCATION

F.2.1 Continuous F.2.2 Rectangular Footings

APPENDIX G – SETTLEMENT GRAPHS

G.1 BUILDING PADS LOCATION

G.1.1 Continuous G.1.2 Rectangular Footings

G.2 HELIPADS LOCATION

G.2.1 Continuous G.2.2 Rectangular Footings

APPENDIX H – CONCRETE DESIGN

H.1 CONSTRUCTION JOINT DETAILS – UNREINFORCED CONCRETE

H.2 REINFORCEMENT & JOINT DETAILS – REINFORCED CONCRETE

H.3 THICKENED EDGE DETAILS

H.4 PORTLAND CEMENT CONCRETE PAVEMENT DESIGN DEPTH

APPENDIX I – GROUNDWATER REPORT

1.0 Background and Scope

This geotechnical investigation is provided to Tammie Mather and the Cleveland National

Forest for the purposes of obtaining surface and sub-surface design criteria for a new helibase located on Kitchen Creek Road in the eastern county of San Diego, California.

The design criteria and recommendations include: 1.) site evaluation with respect to engineering properties of the soils; 2.) evaluate the potential and make recommendations for groundwater development at the site; 3.)develop earthwork recommendations including compaction criteria for site fill materials; 4.) develop foundation recommendations for proposed structures including bearing capacities and estimation of foundation settlements; 5.) provide design recommendations for Portland concrete pavements including landing surfaces, driving surfaces and parking areas; 6.) provide site specific seismic design parameters for buildings including identification of potential hazards due to ground shaking; 7.) provide information as requested with regard to wind load, snow load and frost depth.

The scope of this investigation includes field explorations, sampling and testing of site materials (performed by others), engineering analysis and limited design, and report preparation.

2.0 Project Description

This new center will be designed to house the model S-E64 Erickson Air-Crane helicopter and consist of an office building, a vehicle garage, a hanger for aircraft, two helipads and associated connecting roads, a small parking area, and underground utilities. Water will be provided by development of groundwater on site and sanitary will be disposed of through a constructed septic system. Power will be brought in and any geotechnical required will be provided by others.

It is anticipated that the helicopter will only land unloaded, but for purposes of design it will be assumed that the full maximum gross weight of 42,000 pounds could be encountered on the landing pads. The helipad design will be accomplished using Unified Facilities Criteria, Pavement Design for Airfields (UFC 3-260-02) as a reference. Army & Air Force rigid pavement design is utilized. The travel ways will consist of portland cement concrete and will accommodate a 5-axle fuel truck with a maximum gross vehicle weight of 75,000 pounds and a maximum speed of 10 miles per hour. Parking areas will consist of portland cement concrete and will accommodate passenger vehicles only.

The office building will consist of a 1-story 2480 square foot structure designed to house the personnel and accommodate a 100 pounds per square foot floor load. The 1680 square foot garage will house vehicles while the 12,000 square foot hangar will lodge the Air-Crane helicopter.

Groundwater will be developed at the south end of the site and pumped to underground storage tank in the southwestern corner of the site. The anticipated water use ranges from a maximum normal day-to-day use of 330 gpd to a high use fire season maximum of 3300 gpd. Septic will be on the north side of the office building and hangar. No percolation test results have been provided for this report.

3.0 Geotechnical Investigation

This report is compiled using several common techniques. Field explorations along with sampling and testing of on-site materials provided data which was analyzed using explicit and empirical relationships in accordance with generally accepted procedures. The general procedures are described below. The results are presented in Appendix B, Appendix C, and Appendix D at the back of this report.

3.1 Field Explorations

A number of site visits were made and geotechnical investigations were performed which included use of field observations, cone penetration testing (CPT), shearwave velocity profiling and in-situ sample collection using bulk samples.

An initial site visit occurred on 3 December 2010. The main objective was to determine potential locations for a new well that would supply water to the helibase facility at the feasibility level. Field observations were made in conjunction with map reconnaissance (aerial, geology and topographic), local well history assemblage, and hydrogeological research. The subsequent report is located in the appendices (Appendix I).

Cone penetration testing was performed on 20 June 2011 by Kehoe Testing, Incorporated out of Huntington Beach. Two areas (see map Appendix B.1,CPT Locations) were tested to a depth of 20 feet with a 30-ton, 4-axle direct push rig. Continuous readings of tip stress, sleeve stress, and pore pressure measurements along with soil profiling were provided. Additionally shear wave velocity measurements were obtained at 5-foot intervals.

The following week on 27 June 2011 the seismic testing was performed in the vicinity of CPT-2, where it was anticipated the building would be located. The work was done by Spectrum Geophysics out of Burbank, CA using a technique known as refraction microtremor (ReMi). The result of this testing is a shear wave velocity profile to a depth of 30 meters and an average profile for that depth (Vs30) which can be used in earthquake design. The profile is included in Appendix C.

3.2 Physical Testing

During the week of 7 November 2011, samples were retained by Cleveland National Forest personnel and delivered to Southern California Soil and Testing, Inc. in San Diego for laboratory testing. A map is included in Appendix D.1 Soil Test Locations which shows the sample locations.

Tests included Grain Size Distribution; R-Value (Cal-Test 301); CBR (ASTM 1883); Expansion Index (ASTM D4829); and Maximum Density Testing (ASTM D1557). Laboratory testing of soil samples is performed in order to obtain values that give a better understanding of the site and its subsurface conditions, acquire parameters for design, and make appropriate correlations.

4.0 Site Characteristics

4.1 Geology and Topography

4.1.1 Regional Geology

The proposed helibase site is located in the southeastern part of San Diego County and within Peninsular Ranges Geomorphic Province (Appendix A.1 – Location Map). This province is bounded on the west by the Continental Borderland (including the channel islands and the continental shelf which is cut by deep submarine fault troughs) , the east by the Salton Trough and the north by the Transverse Ranges and the Basin and Range Provinces. The geologic structures within this province are elongated in a northwest-southeast orientation extending from the Santa Monica Mountains more than 900 kilometers down to the tip of Baja.

The Laguna, Cuyamaca, In-Ko-Pah and Jacumba Mountains contained locally within the Peninsular Ranges Batholith (PRB) are remnants of a much larger magmatic arc which formed successively along the west coast of the Pacific Ocean as subduction of the oceanic plate beneath the continental plate started several hundred million years ago (mya). During this time San Diego County existed below sea-level in what is known as a forearc basin, a depression between the trench created by the subducting oceanic crust and the uplifted continental crust. Sediments from the eroding continental margin filled the forearc basin and remnants can be seen today overlaying the PRB in areas as metasedimentary units like the Julian Schist.

As subduction continued, partial melting of the oceanic crust and incorporation of the associated seawater into a hydrothermal solution carried the magma upward to create a volcanic arc, the remnants of which can be seen in a narrow band of highly deformed rocks within the Cuyamaca-Laguna Mountain fault zone (CLM). Dating of the rocks within the CLM puts their formation between 234-160 mya. This band, which is thought to have reached impressive heights in its day perhaps even rivaling the Andes, has long since eroded leaving only a remnant plateau that now demarcates the boundary between the older batholitic rocks (125-100 mya) to the west and the younger, eastern PRB which was emplaced 100-90 mya. Formation of the volcanic arc exposed and metamorphosed sediments in the forearc basin extending westward continental margins above sea-level. Rock units within the CLM typically consist of granodiorite and tonalite plutons which were probably derived from partial melting of the gabbroic crust and mixing with the more siliceous continental crust.

Later two sequential orogenic events emplaced the batholitic rocks to the west and then to the east which comprise the PRB today. The older PRB units were a result of renewed subduction along the western continental margins with the Fallaron Plate (pre-cursor to the Pacific Plate) plunging beneath what is now the North American Plate at a rate of about 2 inches per year. The result was the creation of a new volcanic arc and its underlying magma chamber which may have reached heights of over 5 vertical miles. This process occurred within a span of about 25 million years. Then about 100 mya igneous processes halted for a short time, restarting about 95 mya when a piece of the Fallaron Plate broke off of the main and resumed a more rapid plunge beneath the North American Continent. The increased subduction rate decreased the plunge angle shifting volcanic activity further east. The result was a large mountain range which filled the expanse to the east and reached heights of almost two vertical miles taller than its predecessor to the west.

During the next 20 million years erosion took place at a devastating rate exposing the batholitic roots and resulting in the relief only a few kilometers higher than what we see today.

With the final disappearance of the Fallaron Plate beneath the North American Plate 30 mya, the California coast came in direct contact with the Pacific Plate and subduction, which by this time had moved igneous activity far east into Arizona, ceased. This movement was replaced by the northwest advance of the Pacific Plate which, approximately 10 million years later, caught a piece of the continental crust shearing it from the North American Plate and consequently separating Baja and Southern California from mainland Mexico. This margin which now separates the two plates, known as the San Andreas Fault, has been moving western Southern California along with Baja Mexico at the rate of about 2 inches per year.

4.1.2 Local Geology & Topography

The proposed heliport site lies close to the northeastern margin of a small valley filled with Holocene alluvium. To the east a fan rises gradually about 200 feet and then abruptly to some low lying hills of granitic outcrops. This abrupt change in grade is demarcated on the geology map (El Cajon Quadrangle) by a contact (a change in lithology or rock unit) and potentially the continuation of a northeast-southwest trending fault lineament. To the west the land slopes consistently upward at a grade of less than 5% until it is broken by the slope that forms the southeastern terminus of the Laguna Mountains as they dive into Cameron Valley. This hill slope rises rapidly about 700 feet and is dotted with outcrops of Granite Mountain Tonalite. The approximate elevation of the proposed helibase site is 3360 feet above mean sea level.

The site is located northeast of Cameron Fire Station about 0.5 miles up Kitchen Creek Road in a small broad valley approximately 500 ft. northeast of a confluence with a south draining canyon and southeast of an old shooting area. This confluence also appears to be the intersection of two geologic features, potentially fault traces of undetermined age (Appendix A.5 – Local Geology Map). The general slope of the valley floor is southerly from the mouth of the side canyon and from the northeast toward Cameron Station (~ 3%).

4.2 Soils and Water

The area is composed of Quaternary alluvial sand and sandy silts potentially underlain by the same granitic material which comprise the outcrops on the hills to the west. Annual grasses dominate the valley floor with chaparral lining the hills to east and west sides. The valley was ravaged by fire in the fall of 2007 and few oaks remain in the valley. The drainage north of the site appears to have healthy vegetation growth although the type of vegetation has not been determined (for purposes of predicting persistence of flow). There are no known or observed springs in the area.

CPT Testing was performed at two locations to a depth of 20 ft. No groundwater was encountered in these borings.

4.3 Wind, Snow and Frost

The potential site for the helibase lies at an elevation of 3360 feet in east San Diego County. An anticipated frost depth is approximately 5 inches. A snow load for this elevation has been obtained using the San Bernardino loading of 5 psf from 2000 feet to 3600 feet elevation. The area is quite open except for a scattering of trees more than 100 yards away. As such it conforms to the 2006 IBC Exposure Category C for wind loads. Basic wind speed for a 3-second gust, exposure C is 85 mph.

4.4 Faulting

Most of Southern California is in a seismically active area. The closest fault that is considered an active fault is the Elsinore Fault Zone (Coyote Mountain Branch) located approximately 20 miles to the north east of the site. This fault has documented Holocene activity (within the last 11,000 years) along its entire length with a slip rate of approximately 4-5 mm/yr and a recurrence interval of 600 to 1000 years. However the distance to the fault puts the new helibase well outside the Alquist-Priolo Earthquake zone and negates any potential effect from surface rupture.

Of closer proximity are several “unidentified” Quaternary faults in the immediate vicinity.

These faults have had movement within the last 1.6 million years and are considered by the State Mining and Geology Board to be Potentially Active however are not explicitly identified as Sufficiently Active or Well-defined for the purposes of hazard zoning.

5.0 Discussion of Findings

The following is a discussion of field and laboratory testing results and their relationships to the engineering properties of the site.

5.1 Subsurface Conditions

As previously discussed, the site is located on Holocene alluvial material surrounded on three sides by mountains of granitic rock. An alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads typically at the exit of a canyon onto a flatter plain.

Alluvial fans are often found in desert areas subject to periodic flash floods from nearby thunderstorms in local hills and are common around the margins of the sedimentary basins. The layering resulting from soil deposition is often random and varied with densities similar to those achieved in hydraulic fills – loose and unconsolidated – making them susceptible to liquefaction.

The soil column for CPT-1 generally depicts the typical layering found in alluvial deposits.

Sandy materials are inter-mixed with silty and occasionally clay materials. Much of the material appears to have moderate to high relative densities. However a bed of loose to very loose silty sand appears to exist between 5.5 and 7.5 feet below ground surface (bgs). This could present a problem with long-term settlement and settlement due to liquefaction. Additionally at a depth ranging between 9 and 10.5 feet bgs a layer of clay and silty clay appears in the strata. Based on the cone penetrometer testing and correlated undrained shear strengths, this is a fairly stiff clay, however no in-situ sampling has been done to this depth, so the shrink or swell potential of this material remains unknown.

The CPT-2 location appears to be less variable. The initial 5 feet of soil would be described as dense or very dense. During the initial site investigation it was noted to potentially be a fill material placed in what remains of an old roadbed. Below this layer lies approximately 1.5 feet of loose silt with potentially the same issues as the CPT-1 strata.

At a depth of 10 feet or more in both CPT profiles the soil becomes quite dense and should not pose a problem for bearing, for settlement or for liquefaction.

5.2 Groundwater

No groundwater was observed to the depth of cone penetration testing or 20 feet. Testing was done in late June after a fairly good rain year. Groundwater levels would be anticipated to be high at this time. It can be assumed based on CPT results that groundwater levels are typically below 20 feet in this area. Additional information on groundwater potential for extraction purposes in included in the supplemental report located in Appendix I.

5.3 Soil Properties and Strength Characteristics

The cone penetrometer test results along with gradations, soil classifications, and moisture density relationships have been used to determine strength parameters through accepted methods of correlations. For the purpose of bearing capacity and settlement potential, each soil column has been divided into 2 layers. The upper layer represents the stronger material of silty sand and mixed sand and has an approximate effective friction angle of 34 and 33 degrees respectively for the building area and helipad area. The lower layer appears to be a sandy silt to silt and is a thinner lens ranging in thickness from 1 to 2 feet. It is located between 5 and 8 feet (depending on the site).

The effective friction angles for this material approximate 30 and 28 degrees (building location and helipad location) and are based on average relative densities correlated from CPT values.

The CPT-2 site associates with the building locations. The lens is closer to the surface, but does not appear to be as loose as the layer located at CPT-1. This is favorable as the structures are located here and are more susceptible to movements due to settlement.

The expansion index is very low, showing the upper soil to be non-expansive at both sites.

No remediation will be required.

5.4 Percolation Test

No percolation tests were conducted for this investigation.

6.0 Engineering Seismology

The Coyote Mountain branch of the Elsinore Fault Zone is currently the closest known potential fault hazard. It is a 110-mile long right-lateral transverse (strike-slip) fault located approximately 20 miles north east of the helibase site. The Maximum Probable Earthquake is 6.5 to 7.5 with a return period of approximately 250 years between major ruptures and a slip rate of 4 mm/yr. as determined from Southern California Earthquake Center fault index. Peak Ground Acceleration is approximately

0.23 g’s with a 10% probably of exceedence in 50 years (475 year return period), obtained from the United States Geological Survey’s (USGS) National Seismic Hazards Maps - 2008.

6.1 IBC / NEHRP Seismic Parameters for New Buildings

A seismic survey was used to obtain a shearwave velocity profile (Appendix C.1, Shear

Wave Velocity Profile), in the vicinity of CPT-2, to a depth of 30 meters. The profile was averaged over that depth to obtain an average shearwave velocity of 1,485 ft/s which correlates to Site Class C, Very dense soil and soft rock. Based on a site specific analysis tool and using site coordinates the short period (0.2s) and long period (1.0s) spectral response accelerations for Site Class B have been determined as 1.157g and 0.392g, respectively. Using site class modifiers the 5% damped maximum considered earthquake spectral response acceleration for short and long periods are as follows:

• SMS = 1.157g (Site Class C, short period)

• SM1 = 0.552g (Site Class C, long period)

The Design Spectral Response Accelerations for short and long periods are:

• SDS = 0.771 (Site Class C, short period)

• SD1 = 0.368 (Site Class C, long period)

The full site modified response spectrum is shown in Appendix E.3, Site_Specific_NEHRP_Seismic_Parameters .

6.2 Liquefaction Potential

Soil liquefaction refers to the deformations caused by the generation of excess pore pressures equal to or in excess of the overburden stresses in saturated cohesionless soils. This excess pore pressure is related to cyclic shear stresses in the soil and is dependent on a variety of factors including the density of the soil, the depth to the water table, and the intensity and duration of the anticipated seismic activity. Whether a site will undergo liquefaction, or its resistance to liquefaction is governed by features such as soil type, presence of fines, and void ratio. Sites of cohesionless granular soils with high water tables located in areas of high seismic hazard are particularly susceptible to deformations related to soil liquefaction. The four principle types of liquefaction hazards include:

1. Flow slides

2. Lateral spreading

3. Ground Settlement

4. Surface manifestations (sand boils, ground fissures, etc.)

In the case of the proposed building locations the water table was not located within the upper 20 feet of soil. Additionally the soil below the upper 10 feet is potentially over consolidated or cemented soil. In any case it meets one of the screening criteria in the DMG Special Publication 117, Guidelines for analyzing and mitigating liquefaction hazards in California which states that CPT values over 160 are not considered liquefiable. In the case of CPT-2 the values exceed 160 below 8.5 feet. It is not anticipated at this time that the water table would rise above this level, but there is no historical information which would substantiate this assumption. If this were to be a critical facility which must operate in the event of a major seismic event, then the conservative approach would be to perform a special liquefaction analysis utilizing a 50-foot boring. Based on the added expense and time involve in performing the task in conjunction with the purpose of the facility, additional study is not recommended at this time.

7.0 Design Recommendations

The following sections provide recommendations based on the results of the investigation and subsequent analysis. The proposed site development is geotechnically feasible provided the recommendations are incorporated in the design process. Any deviation of the proposed structure, either in location or concept requires new or supplementary analyses.

Additionally it is important that appropriate recommendations are incorporated into the construction phase of the project.

7.1 Site Preparation, Excavation and Backfill

All earthwork which underlies structural improvements (i.e. buildings, helipads and taxiways, fuel truck travel ways, parking, etc.), including excavation, backfill, and preparation of subgrade, will be performed in accordance with the geotechnical recommendations presented in this report and applicable portions of the grading code of local regulatory agencies. All structural earthwork should be performed under the observation and testing of a qualified geotechnical engineer.

Prior to the start of earthwork, the areas of the proposed improvements will be cleared of all vegetation and debris. The near surface soils in the building areas will be excavated to a minimum depth of 1- foot below the existing ground surface or 6-inches below the bottom of the foundations -whichever is greater. Material containing animal excavations shall be removed and replaced with acceptable fill. Deleterious materials generated from the site clearing should be removed from the construction area and disposed off-site.

Based upon testing some of the material in this area appears suitable as foundation material in its in-situ form. It is granular non-plastic material and non-expansive. However, only material having less than 15% fines (particle size less than 0.02mm) should be placed under and adjacent to foundations which lie within the frost depth (upper 5 inches). Once undesirable material is removed from all improvement locations, the remaining 12 inches underneath the bottom of the foundation and within 5 feet of the proposed structure for buildings and 3 feet for non-building structures should be scarified and re-compacted to 95 percent relative compaction of ASTM D1557 at optimum moisture plus or minus 2 percent. All other areas should be scarified and re-compacted to 90 percent relative compaction of ASTM D1557 at optimum moisture plus or minus 2 percent.

Moisture/Density curves are included in the appendix to this report for design & estimate purposes (Appendix D), but new curves shall be generated for on-site material prior to compaction.

Should the final grade be less than 3 feet below the original grade, scarification and recompaction shall occur to a depth of 3 feet or to the bottom of unsuitable material, whichever is greater.

All unsuitable fill material within the excavation limits shall be removed from the construction area and disposed of off-site.

If additional fill material is required, foundation fill under structures will have the following requirements or as approved by the Forest Service geotechnical engineer:

Foundation Fill. Furnish granular material free of excess moisture, frozen lumps, roots, sod, or other deleterious material and conforming to the following:

(a) Maximum particle size 2 inches

(b) Soil classification, AASHTO M 145 A-1-a

(c) Material passing No. 200 sieve, 6% max.

AASHTO T 27 and T 11

7.2 Foundation Recommendations

Maximum allowable bearing capacity applies to combined dead and sustained live loads.

The allowable bearing pressure may be increased by one third when including transient live loads, such as seismic and wind forces.

Bearing capacities are calculated from Terzaghi’s equations for strip footings and square footings using various widths and depths. These capacities are incorporated into graphs which allow the designer to choose a size and type which best suits the situation for each structure. A factor of safety of 3.0 has been applied to produce the final values. Larger graphs are incorporated into Appendix F.

It should be noted that these bearing capacities incorporates the effects of variability due to layering of material. The closer the bottom of the footing comes to the less desirable material, the lower the design value. If the footing is within 2 feet of the softer material (3 feet below original ground surface), the soft material needs to be removed and replaced with suitable material. In this case I can provide new potentially higher design values.

Expected settlement is highly variable based on foundation type and loading. If the entire slab is expected to act as a single unit, differential settlement should be non-existent and overall settlement should be minimal assuming that the entire slab would never be loaded to its full bearing capacity (assuming a uniform load of 2 tsf). If isolated footings are considered, then differential settlement up to 1.5 inches could be anticipated based on loading and footing sizes. The charts below have been included in the appendix to help anticipate settlement. These charts have been developed for maximum allowable bearing based on footing size and should be worse case scenario. Lighter loading conditions should create smaller amounts of settlement. Larger graphs are incorporated into Appendix G.

In the area of the roads and helipads, an allowable bearing capacity of 3000 psf is reasonable for a large slab. Providing all other requirements of this report are met, the settlement should be less than ½ inches. If other footing configurations are required, additional charts are available in Appendix G.

7.3 Concrete Slabs

Concrete slabs may be placed on compacted fill as outlined in Section 7.1 and meet the requirements of the IBC for the required loading. The moisture content of the subgrade soil will be maintained above optimum moisture until the slab is poured. Any disturbed or yielding soils will be removed and re-compacted to ASTM D 1557 prior to concrete placement.

Floor slabs will be underlain by an impermeable polyethylene membrane where moisture sensitive floor coverings are to be used. The membrane will be at least 6 millimeters (mil) thick and covered by a minimum 2-inch thick layer of moistened (not saturated) sand to both protect the membrane and to promote proper concrete curing.

7.4 Pavement Recommendations

Some variability of soils is expected when work comprises a large site. Recommendations are based on a limited number of samples and assumptions of uniformity are made. Prior to construction, additional testing should be performed and soil conditions verified. Unsuitable material must be removed or design must be altered.

7.4.1 Design Parameters

The following parameters are either directly measured or correlated based on known values and are for use with pavement design.

• Resilient Modulus, MR * 17,400 psi

• Modulus of Subgrade Reaction *1 200 lbs./in3

• California Bearing Ration, CBR 20

• R-Value 60

* Calculated from R-Value *1 Correlated from CBR, R-Value, Relative Density and soil type

7.4.2 Asphalt Pavement Sections

By others.

7.4.3 Portland Cement Concrete Pavement Sections

This section will cover helipad design, taxiways, fuel truck travel ways and parking.

For the purposes of helipad design, under the UFC 3-260-02, the helibase is considered a

Class II, Type B facility. For a 20 year design life the equivalent aircraft (CH-47) passes for a Visual Flight Rules (VFR) helipad is no less than 20,000.

7.4.3.1 Subgrade

Clearing and over-excavation will be done in accordance with Section 7.1 above. In addition the upper 6-inches will be comprised of a base coarse meeting the requirements of Caltrans Class II Base. Compaction requirements are as follows:

Upper 18 inches 95% ASTM D1557 Below 18 inches 90% ASTM D1557

7.4.3.2 Concrete Thickness

Helipad (TLOF) and FATO and taxiway unreinforced concrete shall have a minimum flexural strength, S’C (by 3 pt loading, ASTM C 78) of 550 psi and a minimum thickness of 8.5 inches.

Portland cement travel ways for fuel trucks and vehicles and parking areas shall have a minimum flexural strength, S’C (by 3 pt loading, ASTM C 78) of 550 psi and a minimum thickness of 6 inches.

The free edges of helipad aprons and taxi ways will have a thickened edge. Parking areas will have a thickened edge if vehicle parking terminates on or at edge of slab.

Thickened edges will be 1.25 times the slab thickness and taper to slab thickness in a distance of 3 feet.

7.4.3.3 Concrete Joints and Joint Spacing

The overall length of the slab in any one direction will be limited to a maximum of

50 feet. Construction joints shall be utilized to join slab segments in excess of 50 feet.

Additionally taxi ways will have longitudinal construction joints every 20 feet with lateral construction joints placed at 50-foot intervals. Construction joints may also be utilized in place of transverse contraction joints when it is necessary to finalize a concrete section that will cure before additional placement can be performed. The construction joint will be a doweled butt joint. Construction joint details are in Appendix H.2, Helipads and Taxiways

Construction_Joint_Details_Reinforced.

Spacing of contraction joints shall be between 12 and 15 feet with a depth of at least

25% of the slab thickness and a width of no less than 1/8-inch. The length of the joint in one direction shall not exceed the length in the other direction by more than 25 percent.

Unreinforced concrete sections will utilize dowels at all contraction joints. Contraction joint details are also in Appendix H.2, Contraction_Joint_Details_Reinforced .

Where slabs and taxiways intersect with building concrete expansion joints will be used. They will be installed to surround or to separate from the pavement any structures that project through, into or against the pavements, such as at the approaches to buildings or around drainage inlets. The thickened edge type will be used for these purposes. Filler material shall be the non-extruding type. A preformed material of ¾-inches should be adequate. The length, depth and position of each expansion joint will be sufficient to form a complete and uniform separation between the pavement and the structure concerned. Details for expansion joints are in Appendix H.3, Expansion_Joint .

Transverse contraction joints shall have a depth of at least 25% of the slab thickness and a width of no less than 1/8-inch and shall be utilized every 12 feet with doweling as described in Section 7.4.3.4. Additionally longitudinal joints shall be placed at every 12 feet and in the center of the traveled way when the width is from 13 to 24 feet. Tie Bars are required as in Section 7.4.3.4.

Fuel Truck Travelways

The overall length of the slab in any one direction will be limited to a maximum of 50 feet. Spacing of contraction joints shall be between 12 and 15 feet with a depth of at least 25% of the slab thickness and a width of no less than 1/8-inch. The length of the joint in one direction shall not exceed the length in the other direction by more than 25 percent.

Parking Areas

7.4.3.4 Concrete Reinforcement and Dowels

Reinforcing steel is utilized to reduce the thickness of slabs and in some cases provide continuity across joints which may reduce tie bars and/or dowels sizes. Dowels provide load transfer across sections while keeping concrete sections aligned. Dowels are typically smooth bar which are coated on one half to prevent a concrete bond with the steel. Therefore concrete slabs are allowed relative movement along one axis only.

Tie bars are deformed rebar and are allowed to bond with concrete on both sides of the joint preventing horizontal separation of the slab.

Utilizing the same minimum flexural strength in 7.4.3.2 above, the overall thickness of the helipad slab can be reduced to 7.5 inches by addition of reinforcing steel. In this case the minimum area of the steel required is 0.09 in2/LF in both the longitudinal and transverse directions. This equates to Welded Wire Reinforcement (WWR) of 4x4- W3xW3 with a yield strength of 60 ksi.

Helipads and Taxiways

Placement of reinforcing steel will be at a depth of (hd/4)+1”

Where: hd = thickness of slab

Doweling in unreinforced concrete sections will be accomplished using steel rebar 1-inch in diameter, a minimum of 16 inches in length and spaced at a maximum of 12 inches on center. The exceptions are dowels placed in the contraction joint located next to the free edge of the pavement. These dowels are tie bars and shall be #5 deformed rebar 2’-6” in length and spaced at 2’-6” on center.

The overall length of the dowels in reinforced concrete sections will be of ¾-inch diameter steel a minimum of 16 inches in length and spaced at a maximum of 12 inches on center.

Fuel Truck Travel Ways

Portland Cement travel ways for fuel trucks and vehicles will have an unreinforced slab depth of 6 inches with the following requirements:

Transverse Contraction Joint Dowels 1.25-inch diameter, 18 inches long, 12 inches on center

Longitudinal Joints/Tie Bars #5 deformed rebar, 30 inches long, 36 inches center to center

Construction Joint Dowels 1.25-inch diameter, 18 inches long, 12 inches on center

Parking areas can be unreinforced and shall utilize the same dowels for fuel truck travel ways to provide load transfer between parking areas and travel ways.

Additionally if construction joints are required, dowels of 1-inch diameter and 18 inches in length shall be placed every 12 inches along the length of the joint. In the event a parking area does not terminate in a travel way, the last transverse contraction joint shall utilize tie bars to prevent separation from the adjacent section. Tie bars shall be #5 deformed rebar, 24 inches in length and placed 30 inches on center. Tie bars shall be placed at center thickness of the slab.

Parking Areas

7.5 Miscellaneous Design Parameters

Additional requested design information is as follows:

• Wind o Basic Wind Speed = 85 mph o Exposure Category C

• Ground snow load = 5 psf

• Frost Depth = 5 inches

8.0 Post Investigation/Design Review

Final plans and specifications will be reviewed prior to the construction to confirm that the full intent of the recommendations presented herein have been implemented in the design.

Should unexpected, or changed, conditions be observed during construction the geotechnical engineer will be immediately contacted to allow a sufficient and timely response to the changed condition.

Testing will be performed during construction as required to verify the foundation penetrates and is founded on anticipated soils and that fill is placed and compacted in an acceptable manner as prescribed in this report.

9.0 Closure

The conclusions, recommendations, and opinions presented herein are: 1) based upon the evaluation and interpretation of available information, 2) subject to confirmation of the actual conditions encountered during construction, and 3) based upon the assumption that sufficient observation and testing will be provided during construction.

Tests conducted by the Contractor shall be reviewed by a qualified Forest Service or independent engineer as provided for in the contract. Review shall also be performed by a qualified Forest Service engineer.

10.0 References

AllExperts, Laguna Mountains. http://en.allexperts.com/e/l/la/laguna_mountains.htm

Coduto, D. P. (1994) Foundation Design, Principles and Practices, Prentice Hall, Inglewood Cliffs, NJ, 796 pp.

Coduto, D. P. (1994) Geotechnical Engineering, Principles and Practices, Prentice Hall, Upper Saddle

Cliffs, NJ, 759 pp.

Department of the Navy (1982) Foundations and Earth Structures, Design Manual 7.2, US Government

Printing Office, Washington D.C., 253 pp.

Department of the Navy (1982) Soil Mechanics, Design Manual 7.1, US Government Printing Office, Washington D.C., 364 pp.

USGS Earthquake Hazards Program, Quaternary Fault Maps, http://geohazards.usgs.gov/qfaults/map.php

IBC (2006) International Building Code and Commentary, Vol 2, International Code Council, Country

Club Hills, Il.

Kramer, S.L. (1996). Geotechnical Earthquake Engineering, Prentice Hall, Upper Saddle River, NJ, 653 pp.

National Highway Institute (2002) Subsurface Investigation – Geotechnical Site Characterization, Federal

Highway Administration, Washington D.C., 300 pp.

Relationships between concrete tests;

http://www.pavement.com/Concrete_Pavement/Technical/FATQ/Construction/Strength_Tests.asp

San Diego Probabilistic Hazard Map, http://www.conservation.ca.gov/cgs/rghm/psha/Map_index/Pages/San_Diego.aspx

Southern California Earthquake Center (1999). “Guidelines for Analyzing and Mitigating

Liquefaction in California,” Recommended Procedures for implementation of DMG Special Publication 117, 63 pp.

Unified Facilities Criteria (UFC) (2001). Pavement Design for Airfields (UFC 3-260-02), Army Corps of

Engineers, Washington DC, 538 pp.

United States Department of Agriculture, Forest Service Specifications for Construction of Roads and

Bridges (August 1996), Washington D.C., 637 pp.

http://en.allexperts.com/e/l/la/laguna_mountains.htm�

Walawender, Michael J. 2000. The Peninsular Ranges: A Geologic Guide to San Diego’s Back Country, Kendall Hunt Publishing Co.

Michelle L. H. Bearmar SoCal Province Geotechnical Engineer, USFS Civil Engineer, PE

11.0 Appendices

Appendix A

Maps

A.1 Location Map

A.2 Vicinity Map

A.3 Project Area Map

Project Location UTMs Datum: WGS84 11S 0550572mE, 3620935mN

A.4 Aerial Views

A.4.1 Project Vicinity

A.4.2 Project Area

A.4.3 Project Boundary

A.5 Local Geology Map

A.6 Site Plan

Appendix B

Cone Penetration Testing

B.1 CPT Locations

B.2 CPT Results

B.2.1 CPT-1

B.2.2 CPT-2

Appendix C

Seismic Testing

C.1 Shear Wave Velocity Profile

Appendix D

Soil Testing

D.1 Soil Test Locations

D.2 Plasticity and Classification of Surficial Soils

D.3 Gradation

D.3.1 Building Pads Location

D.3.2 Helipads Location

D.4 Expansion Index D.4.1 Building Pads Location

D.4.2 Helipads Location

D.5 Maximum Density (Proctor) D.5.1 Building Pads Location

D.5.2 Helipads Location

D.6 California Bearing Ratio D.6.1 Building Pads Location

D.6.2 Helipads Location

D.7 R-Value D.7.1 Building Pads Location

D.7.2 Helipads Location

D.8 Summary

Appendix E

Faulting/Seismic

E.1 CGS Fault Map

E.2 USGS Probabilistic Seismic Hazard Map

E.3 Site Specific NEHRP Seismic Parameters

Conterminous 48 States 2003 NEHRP Seismic Design Provisions Latitude = 32.7268 Longitude = -116.4611 Spectral Response Accelerations Ss and S1 Ss and S1 = Mapped Spectral Acceleration Values Site Class B - Fa = 1.0 ,Fv = 1.0 Data are based on a 0.01 deg grid spacing Period Sa (sec) (g)

0.2 1.157 (Ss, Site Class B)

1.0 0.392 (S1, Site Class B)

Conterminous 48 States 2003 NEHRP Seismic Design Provisions Latitude = 32.7268 Longitude = -116.4611 Spectral Response Accelerations SMs and SM1 SMs = Fa x Ss and SM1 = Fv x S1 Site Class C - Fa = 1.0 ,Fv = 1.408

Period Sa (sec) (g)

0.2 1.157 (SMs, Site Class C)

1.0 0.552 (SM1, Site Class C)

Conterminous 48 States 2003 NEHRP Seismic Design Provisions Latitude = 32.7268 Longitude = -116.4611 Design Spectral Response Accelerations SDs and SD1 SDs = 2/3 x SMs and SD1 = 2/3 x SM1 Site Class C - Fa = 1.0 ,Fv = 1.408

Period Sa (sec) (g)

0.2 0.771 (SDs, Site Class C)

1.0 0.368 (SD1, Site Class C)

Conterminous 48 States 2003 NEHRP Seismic Design Provisions Latitude = 32.7268 Longitude = -116.4611 Site Modified Response Spectrum for Site Class C SMs = FaSs and SM1 = FvS1 Site Class C - Fa = 1.0 ,Fv = 1.408

Period Sa Sd (sec) (g) (inches)

0.000 0.463 0.000

0.095 1.157 0.103

0.200 1.157 0.452

0.477 1.157 2.572

0.500 1.104 2.696

0.600 0.920 3.235

0.700 0.788 3.774

0.800 0.690 4.313

0.900 0.613 4.852

1.000 0.552 5.391

1.100 0.502 5.930

1.200 0.460 6.469

1.300 0.424 7.009

1.400 0.394 7.548

1.500 0.368 8.087

1.600 0.345 8.626

1.700 0.325 9.165

1.800 0.307 9.704

1.900 0.290 10.243

2.000 0.276 10.782

Appendix F

Bearing Capacity Graphs

F.1 Building Pads Location

F.1.1 Continuous

F.1.2 Rectangular Footings

F.2 Helipads Location F.2.1 Continuous

F.2.2 Rectangular Footings

Appendix G

Settlement Graphs

G.1 Building Pads Location Settlements are based on maximum allowable bearing pressures for the footing size and depth (below original ground surface). Smaller loads should result in smaller settlements.

G.1.1 Continuous

G.1.2 Rectangular Footings

G.2 Helipads Location Settlements are based on maximum allowable bearing pressures for the footing size and depth (below original ground surface). Smaller loads should result in smaller settlements.

G.2.1 Continuous

G.2.2 Rectangular Footings

Appendix H

Concrete Design

H.1 Construction Joint Details – Unreinforced Concrete

Construction Joint for Unreinforced Concrete

Contraction Joint for Unreinforced Concrete

H.2 Reinforcement & Joint Details – Reinforced Concrete

Slab Reinforcement Plan Details

Welded Wire Fabric or Bar Mat

Slab Reinforcement Section Details

Contraction Joints for Reinforced Concrete Pavements

Construction Joints for Reinforced Concrete Pavements

H.3 Thickened Edge Details

Expansion Joint

3’ MIN

H.4 Portland Cement Concrete Pavement Design Depth

For Traveled areas exclusive of helicopter landing and travel zones

Appendix I

Groundwater Report

Proposed Kitchen Creek Helibase Well Site Investigation and Recommendations Site Visit:

3 December 2010

Attendees:

Jack Vanlear - Requesting party Michelle Bearmar – Geotechnical Engineer

Scope:

Provide information to assist with location of new potable water well for Proposed Helibase off of Kitchen Creek Road on the Descanso Ranger District on the Cleveland National Forest. This information is intended to be a very preliminary investigation to be used as an aid in cost analysis and infrastructure design at the project feasibility level.

Background:

Forest Service is currently in the design feasibility phase for construction of a new helibase to house the heavy helicopter (skycrane) to be moved from Hemet Field. Compound will include a hanger and office space for approximately 6-8 personnel. Two additional hose bib/hydrants will be located on the premises for servicing helicopter. It is anticipated that a well will provide water needs and be pumped to a buried tank reservoir and pressure tank located on site (exact location and elevation to be determined through hydraulic design based on infrastructure needs).

Figure 1 Proposed site from Kitchen Creek Road to the Northwest

Site characteristics and hydrogeology:

The site is located northeast of Cameron Fire Station about 0.5 miles up Kitchen Creek Road in a small broad valley (<500 ft northeast of a confluence w/a south draining canyon) and southeast of the old shooting area. This confluence also appears to be the intersection of two geologic features, potentially fault traces of undetermined age. The general slope is southerly from the mouth of the side canyon and from the northeast toward Cameron Station (~ 3%). The site is located on the upper end of a Holocene alluvium wedge and is underlain by the granitic material known as tonalite. To the east a fan rises gradually about 200 feet and then abruptly to some low lying hills of granitic outcrops. This abrupt change in grade is demarcated on the geology map (El Cajon Quadrangle) by a contact (a change in lithology or rock unit) and potentially the continuation of a northeast-southwest trending fault lineament. To the west the land slopes consistently upward at a grade of less than 5% until it is broken by the slope that forms the southeastern terminus of the Laguna Mountains as they dive into Cameron Valley. This hill slope rises rapidly about 700 feet and is dotted with outcrops of Granite Mountain Tonalite. There are no known or observed springs in the area and these hill slopes and drainages were ravaged by fire in 2007. A few oaks remain in the valley and the drainage north of the site appears to have healthy vegetation growth although the type of vegetation has not been determined (for purposes of predicting persistence of flow). The Forest Service well at Cameron Station however does boast good overall performance through the years.

Figure 2 Low Lying Hills to East

Figure 3 Intersecting Canyon to North

Figure 4 Sharply Rising Mountains to the Northwest - Note Panoramic distortion; road is straight, not curved

Inferred Aquifer and Siting:

This site is likely to the south of the intersecting fault traces where as the helibase would be located to the north. Faults that affect groundwater can serve as transmissive conduits and can also serve as barriers to flow (although no barrier is complete). It is suggested that a well site be selected at the southwestern end of the compound and most proximal to the intersecting lineaments. This provides the best chance for interception of fractures and takes advantage of any ponding of groundwater if the fault acts as an aquitard. The well site should also be located to the west of the fan extending down from the eastern hills. This is most likely the confluence to the two lithologic units and it is probably desirable to stay within the western unit as the eastern unit appears to be more resistant to weathering and maybe fracturing. It is anticipated that alluvial material will extend to a depth of 30 to 50 feet. This material will probably contain some water but is not the target formation and should be sealed off unless it extends down below this depth. It is anticipated that the granitic unit below will contain fractures capable of storing and transmitting water in quantities needed for the new facility.

Adequate fractures should be intercepted within 200-300 feet, but use a depth of 500 feet for design and bid purposes.

Figure 5 Approximate location of new well (location of standing figure). Again panoramic distortion encompasses 180 degrees.

Figure 6 Proposed Well Site Close

Conclusions:

Recommendations made in this very cursory and preliminary report are in part based on a combination of research, observations and conversations (on the phone…