indicative of the strength of the material being pe netrated. The DCP test results are converted to equivalent N’ values for purposes of geotechnical analysis.
The location of the DCP holes are shown on Figure 1 . The DCP logs are presented as Figures 2, 3, 4, 5 and 6. T-1 ( Figure 2) and T-4 (Figure 5) were completed adjacent to the headwall of the landslide.
These holes penetrated soft conditions in the top 2.5 feet below ground surface (BGS), followed by medium stiff soil conditions from approximately 2.5 to 5.0 feet BGS. We interpret these soils as the organic-bearing grayish brown clay soils and olive brown sandy clay soils which have been viewed in the sidewalls of the slope failure areas. Soils below 5.0 feet consist of predominantly medium stiff, stiff and very stiff soils, interpreted to be weathered claystone/mudstone of the Orinda Formation. T-1 had consistently higher blow counts and was completed at a greater distance from the unstable slopes.
T-4 was completed within approximately 3 feet of the slope failure, and soils strengths have likely been affected by the failure of adjacent soils and relaxing of the soil strength adjacent to the failed slopes. DCP holes T-2 and T-3 ( Figures 3 and 4) were completed at the toe of slope at the pinch point of the landslide. These holes penetrated very soft to soft conditions to depths of 4 to 4.5 feet in the saturated landslide flow deposit. Soils became medium stiff to stiff from 4 to 5 feet, and very stiff to hard from 5 to 8.5 feet BGS. DCP hole T-5 ( Figure 6 ) was completed in the pit area of the landslide, at approximately 15 feet below the top of bank. T-5 penetrated very soft conditions to a depth of 3 feet BGS, medium stiff soil to 5 feet BGS, and stiff to hard conditions to the bottom of the hole at approximately 6.5 feet BGS.
Sampling of site soils was also performed to evaluate physical properties of the soils in the shallow subsurface. Hand sampling was performed on the exp osed soils in the top eight (8) feet below adjacent ground surface in the north wall of the slope failure. The north side wall was scraped to expose the in situ soils and sampling of the soils was performed using hand sampling equipment. A log of the soils as exposed in the north side wall is presented as Figure 7. The soils exposed in the side wall consisted of predominantly sandy lean cla y and fat clay soils with moderate to high plasticity.
The Unified Soil Classification System was used to log soil samples as summarized in Figure 8.
GROUNDWATER
The depth of groundwater was not determined during our investigation. We anticipate that ground water may be present at depths greater than approximately 15 to 18 feet below the curb and gutter elevation, the depth of the exposed soil bank failu re. The creek ordinary water elevation is approximately 32 feet below the curb and gutter elevation. Ground water elevation is expected to be located in the zone between 15 feet and 30 feet below the curb and gutter elevation.
LABORATORY SOILS TESTING
Laboratory testing was performed on selected soil samples from the boreholes. Laboratory testing was performed in Questa’s laboratory in general accorda nce with American Society for Testing and Materials (ASTM) standards for moisture content, dry density, Atterberg limits (ASTM D 4318), and particle size analysis (ASTM D 422).
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Geotechnical Evaluation
Moisture Content (ASTM D 2216)
Moisture content testing was performed on soil samples collected from the side wall at the northeast corner of the slope failure. Results of moisture content testing are summarized on the side wall log (Figure 6). Soils in the upper 1.5 feet had a moisture cont ent of 18 percent. Soils below 1.5 feet ranged from 25 to 28 percent moisture content.
Atterberg Limits (ASTM D 4318- Liquid Limit, Plastic Limit and Plasticity Index) Atterberg limits tests have been performed on two s oil samples from the Northwest side wall.
Atterberg limits, expressed as the plastic limit and the liquid limit, are defined as the moisture content, in percent of a soil at defined boundaries between plastic and brittle states, and liquid and plastic states, respectively. The plasticity index is the range of moisture at which soil behaves plastically, defined numerically as the difference between the liquid and plastic limits. Atterberg limits are used as an aid in understanding soil properties such as compressibility, permeability, and expansion potential.
Soils with medium to high plasticity indices are more susceptible to sliding and to losing soil strength as they absorb water. Results of Atterberg limits testing are summarized on the side wall log for NW- 1 and in Table 1 below. The results are also presented in Figure 9. Overall, soils at the site typically have medium to high plasticity, indicating a high l ikelihood of losing soil strength as they absorb moisture and expand.
Table 1. Results of Atterberg Limits Testing
Sample Number Liquid Limit
(%)
Plastic Limit
(%)
Plasticity Index
% Passing
#200 Sieve
NW-1, 1.5-4 ft BGS 48 21 27 70.1
NW-1, 7- 8 ft BGS 50 19 31 83.8
Particle Size Analysis
Particle size analysis testing was performed in acc ordance with ASTM D 422. Results of testing of the Northeast side wall testing are presented on Figures 10 and 11.
SEISMICITY AND GEOLOGY
Regional Seismicity
The project site is located within the Coast Ranges Geomorphic Province of California, a region of northwest trending ridges and valleys that stretche s along much of the California Coast and is dissected by only a few structural depressions, the largest of which are San Francisco and San Pablo Bays. The ridges and valleys trend northwest to southeast due to fault geometry along the transform plate boundary between the North American and Pacific Plates. Scientists estimate as much as 5 to 6 centimeters (12 to 15 inches) of strain accumulates annually along the margin between the Pacific and North American Tectonic Plates. This strain is peri odically released by fault slip that generates earthquakes along the San Andreas Fault System. For this reason the Bay Area is among the most May 30, 2023
Geotechnical Evaluation
seismically active regions in the United States and there exists an approximately 72 percent chance of a major earthquake (Magnitude 6.7 or greater) in the San Francisco region within the next 30 years. 1
Faulting
The nearest active fault trace in relation to the project site is the Hayward Fault, located approximately 2 miles to the southwest. Other nearby active faults include the San Andreas Fault located 18 miles southwest, the Rodgers Creek Fault 14 miles north, the Concord-Green Valley Fault located 12 miles northeast, and the Calaveras Fault 16 miles southeast.
Table 2 presents a summary of the regional active faults that could impact the site. No faults zoned as active by the State of California Geological Survey cross the subject property. The risk of fault rupture is considered low. The project site is not located within an Alquist-Priolo Earthquake Fault Zone. The nearest Alquist-Priolo Earthquake Fault Zone is for the Hayward fault, 2 miles to the northeast
2. Table 2. Regional Faults and Activity
FAULT
NAME
Distance
From
Site (mi)
Direction
From Site
Last
Surface
Rupture
Status
Maximum Moment
Magnitude
(Richter M)
Hayward 2 Southwest Historic Active 6.9
San Andreas 18 Southwest Historic Active 7.9
Concord 12 Northeast Historic Active 6.5
Rodgers Creek 14 North Holocene Active 6.9
West Napa 15 Northeast Holocene Active 6.5
Green Valley 13 Northeast Holocene Active 6.6
Calaveras 16 Southeast Holocene Active 6.9
Seal Cove 30 Southwest Holocene Active 7.4
Greenville 32 Southeast Historic Active 7.3
Site Geology
A geologic map of the Richmond Quadrangle shows the site as being underlain by the Orinda Formation, a mixture of weakly indurated claystone, siltstone, sandstone and conglomerate. In the project site area the Orinda Formation is predomina ntly claystone and siltstone with fine gravel.
Figure 12 presents a Geologic Map of the area prepared by Dibblee and Minch (2005)
3. Bedrock geology is shown on the Preliminary Geologic Map emphasizing bedrock formations in Contra Costa County, California
4. This map indicates that the site is underlain by bedrock consisting
1 Field, E.H., and 2014 Working Group on California Earthquake Probabilities, 2015, UCERF3: A new earth quake forecast for California’s complex fault system: U.S . Geological Survey 2015–3009, 6 p. 2 California Geological Survey, 2010, Fault Activity Map of California, Geologic Data Map No. 6. 3 Dibblee, T.W. and Minch, J.A., 2005, Geologic map of the Richmond quadrangle, Contra Costa & Alameda Counties, California, Dibblee Geological Foundation, Dibblee Foundation Map DF-147, 1:24,000. 4 United States Geological Survey, 1994, Preliminary Geologic Map Emphasizing Bedrock Formations in Con tra Costa County, California, Open File Report 94-622.
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Geotechnical Evaluation
of Tertiary age sedimentary rocks including conglomerate, sandstone and siltstone. This mapping was also used in a later geologic map of the San Francisco Bay region 5.
The Orinda Formation is part of the Contra Costa Group, which includes late Miocene to Pliocene bedrock formations such as the Orinda Formation, the Moraga Formation, the Siesta Formation, and the Mulholland Formation, among others. The Contra Costa Group includes terrigenous sediments, stream deposits, lacustrine deposits and volcanic rocks
6. Previous investigations performed by Questa Engineering for nearby sites found the Orinda Formation present in the subsurface underlying Valley View Road nearby to the east of De Anza High School
7. The Orinda Formation was found to consist of Olive Yellow and Light Olive Brown Silty Claystone which was moderately weathered, friable, with low h ardness. The decomposed bedrock was generally found to consist of light yellow brown sandy fat clay. These descriptions match the soils and bedrock exposed in the site slopes and in the creek bed.
SLOPE STABILITY
A landslide and slope stability map prepared by Tor Nilsen 8 of the US Geological Survey (1973)
mapped the site at the edge of a potentially large landslide which would include Salvino Court and adjacent areas ( Figure 13) . Other geologic maps of the area do not show this large landslide, but based on observations of this site a nd the site vicinity, it seems likely that the mapping by Nilsen is correct and a large landslide is present beneath the area. This landslide likely includes portions of the underlying bedrock, the Orinda Formation (Contra Costa Group), which is a weakly-indurated relatively low strength , sedimentary formation. Deep seated landslides such as these were formed during portion s of the Pleistocene when higher rainfall was experienced in the region. The deep-seated landsli des are generally dormant, until modifications in the environment or grading in the area expose th e instabilities. A contemporary slope stability map of the area included in the map prepa red by the California Division of Mines and Geology (now the California Geological Survey) in 1 973 9, did not include detailed mapping in the El Sobrante area to the northeast of San Pablo Dam Road. At the time, the project area was not part of the City of Richmond, but was in uninco rporated Contra Costa County. The limited slope stability mapping completed by the State at the time did not show the site or site vicinity as being in a landslide area.
5 Graymer, R.W., Moring, B.C., Saucedo, G.J., Wentworth, C.M., Brabb, E.E., and Knudsen, K.L., 2006, Ge ologic map of the San Francisco Bay region, U.S. Geological Survey, Scientific Investigations Map SIM-2918, 1 :275,000. 6 Creely, S., Savage, D.E., and Ogle, B.A., 1982, Str atigraphy of Upper Tertiary Nonmarine rocks of cent ral Contra Costa Basin, California, in Ingersoll, R.V., ed., C enozoic Nonmarine deposits of California and Arizon a: Pacific Section, Society of Economic Paleontologists and Mineralogists, p. 11–22 7 Questa Engineering Corporation, 2001, Final Geotec hnical Investigation Report for Valley View Road Pa vement Rehabilitation Project, Richmond, California, prepa red for the City of Richmond Engineering Division. 8 United States Geological Survey, 1973, Preliminary Photointerpretation Map of Landslide and Other Sur ficial Deposits of the Concord 15-minute Quadrangle and the Oakland West, Richmond, and Part of the San Quentin 71/2- minute Quadrangles, Contra Costa and Alameda Counties, California, Map MF-493. 9 California Division of Mines and Geology, 1973, Ge ological and Geophysical Investigations for Tri-Cities Seismic Safety and Environmental Resources Study, Preliminary Report 19, Plate 6- Landslide Map May 30, 2023
Geotechnical Evaluation
AERIAL PHOTOGRAPH REVIEW
We reviewed aerial photographs available on Google Earth Pro. The photographs available range in age from 1939 to July of 2022. In 1939, t he site is mostly grass land covered, and trees are limited to a smaller riparian area around Wilki e Creek. Large meander bends are present in the creek at the site area and apparent unstable sl opes are common along the creek banks. The large meander bends in the creek are located in the same area as they are today at the landslide toe at the creek.
Aerial photograph from July 1993 shows the site bef ore the residence was constructed at 2929 Salvino Court. The area of the landslide is well v egetated with tree coverage. The residence location is clear of trees. By July of 2002, the r esidence had been constructed and most of the site is covered by tree canopy. In aerial photogra phs from 2002 to 2015, the slope area appears to be mostly covered by tree canopy and there are n o visible instabilities. In October 2015, a large tree appears to be dead; this is likely the Pine tree stump still present at the edge of the slide failure. In aerial photographs from November, 2016, the tree has been removed (stump remains).
In June of 2019, large areas of eroded soil appear to be present below the tree stump and the wooden fence separating private property from Santa Rita Road. The most recent aerial photograph is from July 10, 2022, and in this photo graph the slope appears to be experiencing slope instabilities which extend upslope to approxi mately 20 feet from the curb at Santa Rita Road. Following these aerial photographs, the slid e area has continued to expand and the failed bank is now located within 3 to 4 feet of the curb at the road. The fence is no longer present.
GEOTECHNICAL RECOMMENDATIONS
Based on our site observations and results of our G eotechnical Evaluation of the site we recommend that Santa Rita Road be protected from sl ope failure by installation of a Drilled Soldier Pile Stitch Wall or Drilled Soldier Pile La gging Wall. The two structures would use the same basic construction using 50-foot deep, 30-inch diameter drilled pier holes to install H- beams which would have poured concrete installed fo r support. A stitch wall would utilize arching between adjacent piles to retain soil and b e backfilled with concrete to approximately 15 feet BGS and the upper section would be backfilled with CLSM, which could be excavated if needed to add lagging. A lagging wall would be backfilled with concrete up to approximately 15 feet BGS and wood lagging would be installed betwee n piles to support the soil and concrete curb structure behind it. Based on current conditi ons at the area of the slope instability, it would appear that at least part of the wall will require wood lagging to support the soil behind the wall.
The sides of the slope failure adjacent to City of Richmond property along the north end of the slope failure will also require stabilization to re duce the potential for further failure. The steepes t part close to the road could be stabilized by conti nuation of the Soldier Pile Wall. A potentially effective alternate method would be to plant the ar ea with live willow stakes and other fast growing types of native vegetation. This type of p lanting can be done in the riparian habitat area without a permit. However, planting alone on the s teep slopes may not be effective in long term stabilization.
May 30, 2023
Geotechnical Evaluation
The south side of the slope failure area, which is located on private property, is also subject to further slope failure. This area could also be sta bilized by continuing the Soldier Pile Wall in that area. Planting with live willow stakes and ot her plant materials could also be an effective alternative method of stabilization.
The toe of the landslide at the creek, which is loc ated on private property, continues to be unstable. As scouring of the soil occurs at the to e during high water events in the creek, the soils are undercut and slide into the void left by the sc ouring process. The long-term stabilization of the slide at the creek will likely require a rock r evetment or similar structure to retain the soils up slope and provide protection from creek scour.
Foundation Design Measures- Retaining Wall
Cast-in-place drill holes should penetrate the surf ace soils consisting of organic-rich sandy clay and sandy clay soils and extend into the underlying formation consisting of silty claystone and other rocks within the Orinda Formation. Drilled c ast-in-place concrete piers should be a minimum of 30 inches in diameter and should be desi gned to support vertical and uplift loads based on a skin friction of 500 psf in the clay soi ls and claystone bedrock, neglecting the upper three feet of soils. The recommended skin friction is for dead plus live loads and can be increased by 33 percent for total loads including w ind or seismic forces. End bearing should be neglected due to the difficulty in cleaning out sma ll diameter pier holes. Resistance to lateral loads should be based on passive pressures using an equivalent fluid weight of 250 pcf over a width of two pier diameters on the portion of the piers extending into firm supporting claystone.
Retaining Wall Design Parameters
Retaining walls at the site must be designed to res ist lateral earth pressures plus additional lateral pressures that may be caused by surcharge loads such as heavy vehicles and equipment. Walls and shoring that are free to rotate should be designed for active lateral earth pressures. If walls or shoring are restrained by rigid elements to prevent rotation, then they should be designed for at-rest earth pressures. Retaining walls backfilled with sandy cl ay should be designed to resist lateral earth pressures due to an equivalent fluid having unit weight as shown in Table 3.
TABLE 3. Retaining Wall Design Parameters Summary
Active
Pressure
(level
backfill)
pounds per
cubic foot
(pcf)
At-Rest
Earth
Pressure
(level
backfill)
pcf
Passive
Pressures
Allowable
pcf
Lateral Surcharge Load (H 20
loading) pounds per square foot
(psf) for retaining walls
adjacent to streets or parking
areas
Sandy Clay
Backfill
45 65 250 250
This wall is considered an emergency measure that i s a temporary wall structure. The seismic conditions for a permanent structure should be determined by adding the pressures from earthquake May 30, 2023
Geotechnical Evaluation
loading to active pressure on the retaining walls. All permanent walls greater than 6 feet in height should include seismic pressure. We recommend an incremental seismic pressure of 29H in pounds per square foot (psf), where H is the height of the retaining wall in feet. The pressure distribution may be considered to be an inverted triangle with the maximum pressure at the top and zero on the bottom.
The resultant of this force may be assumed to be located at 1/3 the height of the wall below the top of the wall. Unit weight of the retained soils is approximately 120 pcf.
Fence Protection Measures
Following wall installation, we recommend that a permanent fence be installed along the area adjacent to the wall to protect the public. A standard 6-fo ot high chain link fence should be adequate protection. A gate or other access point should be included in the fence.
Guardrail
A guardrail should be constructed between the retaining wall and the street to protect vehicles in the event of an accident. A guardrail should be designed and constructed in accordance with Caltrans Standard Specifications and Details.
CONCLUSIONS
Provided that the site is properly prepared and the structures are designed and constructed as recommended, we estimate that normal post-construction settlement will be small, less than 1.0 inch.
We estimate that differential settlements over a distance of 25 feet would be small, up to 0.5 inches. It is our opinion that the proposed construction will not adversely affect the site stability provided that our design recommendations are followed.
Seismically Induced Settlement
No potentially liquefiable sands are likely to be present in the location area. Sandy lean clay and fat clay soils were observed in the proposed construction area. Seismically induced settlement is unlikely to occur in this area.
Seismically Induced Slope Failure
Seismically induced landslides could occur in the future at the project site. The exposed side slopes in the slide area are very steep, ranging from 45 degrees to near vertical. In the event of earthquake induced strong ground shaking, these exposed slopes are likely to fail. Additional trees, vegetation and soil would likely fall into the failure area. The improvements located along Santa Rita Road would also be prone to failure including the curb and gutter, pavement, sanitary sewer lines, potable water lines and other utilities if present.
Construction Services
During construction we should observe installation of the site improvements including excavations and drilled pier construction. This will allow us to observe that subsurface conditions are as
PHOTOGRAPHS
P
Photograph 1. Landslide from Creek below on 2/5/2023. Photograph 2. Toe of slide at Wilkie Creek 2/5/2023
Photograph 3. South wall of landslide on 2/5/2023. Photograph 4. South wall of slide on 2/5/2023.
Photograph 5. North wall of landslide on 2/5/2023. Photograph 6. Down slope view of landslide on 2/5/2023.
Photograph 7. North & East areas of landslide 3/12/2023. Photograph 8. South area of landslide 3/12/2023.
Photographs 9 and 10. Landslide covered in plastic sheeting on 3/14/2023.
Photograph 11. Fence and Tree fall into slide on 3/30/2023. Photograph 12. Tree partially removed and slope recovered with plastic sheeting as seen on 4/10/2023.
Photograph 13. Slide adjacent to Santa Rita Rd on 5/24/23. Photograph 14. Site conditions on 5/24/23.
Photograph 15. Landslide at creek as of 5/24/23. Photograph 16. Landslide at Santa Rita Rd as of 5/24/23.
Photograph 17. Cracking and offset curb & gutter 5/24/23.
F
IGURES
FIGURE
1 2929 Salvino Court at Santa Rita Rd
Site Plan
DATE: 4/24/2023
PROJECT: Salvino Court
PROJECT NO.: 2200159
SOURCE: Google Earth
APPROVED:
Appro ximate Landslide Margins
Location map
T-5
T-3
T-2
T-4
T-1
WILDCAT DYNAMIC CONE LOG Page 1 of 2
Questa Engineering Figure 2
1220 Brickyard Cove Road, Suite 206 PROJECT NUMBER: 2200159 Richmond, CA 94806 DATE STARTED: 03-31-2023
DATE COMPLETED: 03-31-2023
HOLE #: T-1
CREW: MWF, CJG SURFACE ELEVATION: 176 (approx. ft msl)
PROJECT: Salvino Ct Landslide WATER ON COMPLETION:
ADDRESS: 2929 Salvino Ct HAMMER WEIGHT: 35 lbs.
LOCATION: El Sobrante, CA CONE AREA: 10 sq. cm
BLOWS RESISTANCE GRAPH OF CONE RESISTANCE T ESTED CONSISTENCY DEPTH PER 10 cm Kg/cm² 0 50 10 0 150 N' NON-COHESIVE COHESIVE - 1 4.4 • 1 VERY LOOSE VERY SOFT
- 3 13.3 ••• 3 VERY LOOSE SOFT
- 1 ft 3 13.3 ••• 3 VERY LOOSE SOFT
- 2 8.9 •• 2 VERY LOOSE SOFT
- 2 8.9 •• 2 VERY LOOSE SOFT
- 2 ft 3 13.3 ••• 3 VERY LOOSE SOFT
- 3 13.3 ••• 3 VERY LOOSE SOFT
- 5 22.2 •••••• 6 LOOSE MEDIUM STIFF
- 3 ft 7 31.1 ••••••••• 8 LOOSE MEDIUM STIFF - 1 m 5 22.2 •••••• 6 LOOSE MEDIUM STIFF
- 5 19.3 ••••• 5 LOOSE MEDIUM STIFF
- 4 ft 5 19.3 ••••• 5 LOOSE MEDIUM STIFF
- 5 19.3 ••••• 5 LOOSE MEDIUM STIFF
- 5 19.3 ••••• 5 LOOSE MEDIUM STIFF
- 5 ft 8 30.9 •••••••• 8 LOOSE MEDIUM STIFF - 11 42.5 •••••••••••• 12 MEDIUM DENSE STIFF
- 12 46.3 ••••••••••••• 13 MEDIUM DENSE STIFF
- 6 ft 8 30.9 •••••••• 8 LOOSE MEDIUM STIFF - 7 27.0 ••••••• 7 LOOSE MEDIUM STIFF
- 2 m 11 42.5 •••••••••••• 12 MEDIUM DENSE STIFF
- 7 ft 11 37.6 •••••••••• 10 LOOSE STIFF
- 23 78.7 •••••••••••••••••••••• 22 MEDIUM DENSE VERY STI FF - 18 61.6 ••••••••••••••••• 17 MEDIUM DENSE VERY STIFF
- 8 ft 14 47.9 ••••••••••••• 13 MEDIUM DENS E STIFF - 14 47.9 ••••••••••••• 13 MEDIUM DENSE STIFF
- 12 41.0 ••••••••••• 11 MEDIUM DENSE STIFF
- 9 ft 10 34.2 ••••••••• 9 LOOSE STIFF
- 10 34.2 ••••••••• 9 LOOSE STIFF
- 15 51.3 •••••••••••••• 14 MEDIUM DENSE STIFF
- 3 m 10 ft 14 47.9 ••••••••••••• 13 MEDIUM DENSE STI FF - 8 24.5 ••••••• 6 LOOSE MEDIUM STIFF
- 16 49.0 •••••••••••••• 13 MEDIUM DENSE STIFF
- 15 45.9 ••••••••••••• 13 MEDIUM DENSE STIFF
- 11 ft 18 55.1 ••••••••••••••• 15 MEDIUM DEN SE STIFF - 14 42.8 •••••••••••• 12 MEDIUM DENSE STIFF
- 12 36.7 •••••••••• 10 LOOSE STIFF
- 12 ft 12 36.7 •••••••••• 10 LOOSE STIFF
- 15 45.9 ••••••••••••• 13 MEDIUM DENSE STIFF
- 16 49.0 •••••••••••••• 13 MEDIUM DENSE STIFF
- 4 m 13 ft 27 82.6 ••••••••••••••••••••••• 23 MEDIU M DENSE VERY STIFF C:\My Documents\Wildcat\WC_XL97.XLS
HOLE #: T-1 WILDCAT DYNAMIC CONE LOG Page 2 of 2
PROJECT: Salvino Ct Landslide Figure 2 PROJECT NUMBER: 2200159
BLOWS RESISTANCE GRAPH OF CONE RESISTANCE T ESTED CONSISTENCY DEPTH PER 10 cm Kg/cm² 0 50 10 0 150 N' NON-COHESIVE COHESIVE - 22 60.9 ••••••••••••••••• 17 MEDIUM DENSE VERY STIFF
- 29 80.3 ••••••••••••••••••••••• 22 MEDIUM DENSE VERY ST IFF - 14 ft 15 41.6 •••••••••••• 11 MEDIUM DENSE S TIFF - 13 36.0 •••••••••• 10 LOOSE STIFF
- 21 58.2 •••••••••••••••• 16 MEDIUM DENSE VERY STIFF
- 15 ft 18 49.9 •••••••••••••• 14 MEDIUM DENS E STIFF - 21 58.2 •••••••••••••••• 16 MEDIUM DENSE VERY STIFF
- 19 52.6 ••••••••••••••• 15 MEDIUM DENSE STIFF
- 16 ft 16 44.3 •••••••••••• 12 MEDIUM DENSE S TIFF - 5 m 15 41.6 •••••••••••• 11 MEDIUM DENSE STIFF
- 14 35.6 •••••••••• 10 LOOSE STIFF
- 17 ft 17 43.2 •••••••••••• 12 MEDIUM DENSE S TIFF - 18 45.7 ••••••••••••• 13 MEDIUM DENSE STIFF
-
- 18 ft
-
-
- 19 ft
-
- 6 m
- 20 ft
-
-
- 21 ft
-
-
- 22 ft
-
-
- 7 m 23 ft
-
-
- 24 ft
-
-
- 25 ft
-
-
- 26 ft
- 8 m
-
- 27 ft
-
-
- 28 ft
-
-
- 29 ft
-
- 9 m
C:\My Documents\Wildcat\WC_XL97.XLS
WILDCAT DYNAMIC CONE LOG Page 1 of 1
Questa Engineering Figure 3
1220 Brickyard Cove Road PROJECT NUMBER: 2200159
Richmond, CA 94801 DATE STARTED: 04-19-2023
DATE COMPLETED: 04-19-2023
HOLE #: T-2
CREW: MWF, SAF, CJG SURFACE ELEVATION: 156 (approx. ft msl) PROJECT: Salvino Ct LS WATER ON COMPLETION: No GW
ADDRESS: 2929 Salvino Ct HAMMER WEIGHT: 35 lbs.
LOCATION: Richmond, Ca CONE AREA: 10 sq. cm
BLOWS RESISTANCE GRAPH OF CONE RESISTANCE T ESTED CONSISTENCY Absolute Soil Description DEPTH
PER 10 cm
(4") Kg/cm² 0 50 100 1 50 N' NON-COHESIVE COHESIVE N' - 1 4.4 • 1 VERY LOOSE VERY SOFT 1 Sandy Clay, Wet,
- 0 0.0 0 VERY LOOSE VERY SOFT 0 Landslide material
- 1 ft 0 0.0 0 VERY LOOSE VERY SOFT 0
- 2 8.9 •• 2 VERY LOOSE SOFT 2
- 0 0.0 0 VERY LOOSE VERY SOFT 0
- 2 ft 0 0.0 0 VERY LOOSE VERY SOFT 0
- 0 0.0 0 VERY LOOSE VERY SOFT 0
- 0 0.0 0 VERY LOOSE VERY SOFT 0
- 3 ft 1 4.4 • 1 VERY LOOSE VERY SOFT 1
- 1 m 0 0.0 0 VERY LOOSE VERY SOFT 0
- 0 0.0 0 VERY LOOSE VERY SOFT 0
- 4 ft 0 0.0 0 VERY LOOSE VERY SOFT 0
- 10 38.6 ••••••••••• 11 MEDIUM DENSE STIFF 11 Native soil - 6 23.2 •••••• 6 LOOSE MEDIUM STIFF 6
- 5 ft 7 27.0 ••••••• 7 LOOSE MEDIUM STIFF 7 - 10 38.6 ••••••••••• 11 MEDIUM DENSE STIFF 11
- 13 50.2 •••••••••••••• 14 MEDIUM DENSE STIFF 14
- 6 ft 14 54.0 ••••••••••••••• 15 MEDIUM DE NSE STIFF 15 - 20 77.2 •••••••••••••••••••••• 22 MEDIUM DENSE VERY STI FF 22 - 2 m 18 69.5 •••••••••••••••••••• 19 MEDIUM DENSE VERY STIFF 19 - 7 ft 15 51.3 •••••••••••••• 14 MEDIUM DEN SE STIFF 14 - 30 102.6 ••••••••••••••••••••••••••••• 25+ MEDIUM DENS E VERY STIFF 29 - 24 82.1 ••••••••••••••••••••••• 23 MEDIUM DENSE VERY ST IFF 23 - 8 ft 19 65.0 •••••••••••••••••• 18 MEDIUM DENSE VERY STIFF 18 - 20 68.4 ••••••••••••••••••• 19 MEDIUM DENSE VERY STIFF 1 9 - 44 150.5
••••••••••••••••••••••••••••••••••••••••••• 25+ DENSE HARD 42 - 9 ft
-
-
- 3 m 10 ft
-
-
-
- 11 ft
-
-
- 12 ft
-
-
- 4 m 13 ft
WILDCAT DYNAMIC CONE LOG Page 1 of 1
Questa Engineering Figure 4
1220 Brickyard Cove Road PROJECT NUMBER: 2200159
Richmond, CA 94801 DATE STARTED: 04-19-2023
DATE COMPLETED: 04-19-2023
HOLE #: T-3
CREW: MWF, SAF, CJG SURFACE ELEVATION: 156 (approx. ft msl) PROJECT: Salvino Ct LS WATER ON COMPLETION: No GW
ADDRESS: 2929 Salvino Ct HAMMER WEIGHT: 35 lbs.
LOCATION: Richmond, Ca CONE AREA: 10 sq. cm
BLOWS RESISTANCE GRAPH OF CONE RESISTANCE T ESTED CONSISTENCY Absolute Soil Description DEPTH
PER 10 cm
(4") Kg/cm² 0 50 100 1 50 N' NON-COHESIVE COHESIVE N' - 0 0.0 0 VERY LOOSE VERY SOFT 0
- 0 0.0 0 VERY LOOSE VERY SOFT 0
- 1 ft 0 0.0 0 VERY LOOSE VERY SOFT 0
- 0 0.0 0 VERY LOOSE VERY SOFT 0
- 0 0.0 0 VERY LOOSE VERY SOFT 0
- 2 ft 0 0.0 0 VERY LOOSE VERY SOFT 0
- 0 0.0 0 VERY LOOSE VERY SOFT 0
- 0 0.0 0 VERY LOOSE VERY SOFT 0
- 3 ft 3 13.3 ••• 3 VERY LOOSE SOFT 3
- 1 m 4 17.8 ••••• 5 LOOSE MEDIUM STIFF 5
- 4 15.4 •••• 4 VERY LOOSE SOFT 4
- 4 ft 6 23.2 •••••• 6 LOOSE MEDIUM STIFF 6 - 5 19.3 ••••• 5 LOOSE MEDIUM STIFF 5
- 4 15.4 •••• 4 VERY LOOSE SOFT 4
- 5 ft 7 27.0 ••••••• 7 LOOSE MEDIUM STIFF 7 - 14 54.0 ••••••••••••••• 15 MEDIUM DENSE STIFF 15
- 20 77.2 •••••••••••••••••••••• 22 MEDIUM DENSE VERY STI FF 22 - 6 ft 21 81.1 ••••••••••••••••••••••• 23 M EDIUM DENSE VERY STIFF 23 - 20 77.2 •••••••••••••••••••••• 22 MEDIUM DENSE VERY STI FF 22 - 2 m 45 173.7
•••••••••••••••••••••••••••••••••••••••••••••••••• 25+ DENSE HARD 49 - 7 ft
-
-
- 8 ft
-
-
- 9 ft
-
-
- 3 m 10 ft
-
-
-
- 11 ft
-
-
- 12 ft
-
-
- 4 m 13 ft Claystone
WILDCAT DYNAMIC CONE LOG Page 1 of 2
Questa Engineering Figure 5
1220 Brickyard Cove Road, Suite 206 PROJECT NUMBER: 2200159 Richmond, CA 94806 DATE STARTED: 04-19-2023
DATE COMPLETED: 04-19-2023
HOLE #: T-4
CREW: MWF, CJG, SAF SURFACE ELEVATION: 174 (approx. ft msl) PROJECT: Salvino Ct Landslide WATER ON COMPLETION:
ADDRESS: 2929 Salvino Ct HAMMER WEIGHT: 35 lbs.
LOCATION: El Sobrante, CA CONE AREA: 10 sq. cm
BLOWS RESISTANCE GRAPH OF CONE RESISTANCE T ESTED CONSISTENCY DEPTH PER 10 cm Kg/cm² 0 50 10 0 150 N' NON-COHESIVE COHESIVE - 1 4.4 • 1 VERY LOOSE VERY SOFT
- 2 8.9 •• 2 VERY LOOSE SOFT
- 1 ft 5 22.2 •••••• 6 LOOSE MEDIUM STIFF
- 3 13.3 ••• 3 VERY LOOSE SOFT
- 5 22.2 •••••• 6 LOOSE MEDIUM STIFF
- 2 ft 3 13.3 ••• 3 VERY LOOSE SOFT
- 3 13.3 ••• 3 VERY LOOSE SOFT
- 5 22.2 •••••• 6 LOOSE MEDIUM STIFF
- 3 ft 4 17.8 ••••• 5 LOOSE MEDIUM STIFF
- 1 m 4 17.8 ••••• 5 LOOSE MEDIUM STIFF
- 5 19.3 ••••• 5 LOOSE MEDIUM STIFF
- 4 ft 6 23.2 •••••• 6 LOOSE MEDIUM STIFF
- 7 27.0 ••••••• 7 LOOSE MEDIUM STIFF
- 6 23.2 •••••• 6 LOOSE MEDIUM STIFF
- 5 ft 7 27.0 ••••••• 7 LOOSE MEDIUM STIFF - 6 23.2 •••••• 6 LOOSE MEDIUM STIFF
- 9 34.7 •••••••••• 9 LOOSE STIFF
- 6 ft 9 34.7 •••••••••• 9 LOOSE STIFF
- 12 46.3 ••••••••••••• 13 MEDIUM DENSE STIFF
- 2 m 11 42.5 •••••••••••• 12 MEDIUM DENSE STIFF
- 7 ft 9 30.8 •••••••• 8 LOOSE MEDIUM STIFF - 7 23.9 •••••• 6 LOOSE MEDIUM STIFF
- 6 20.5 ••••• 5 LOOSE MEDIUM STIFF
- 8 ft 7 23.9 •••••• 6 LOOSE MEDIUM STIFF
- 7 23.9 •••••• 6 LOOSE MEDIUM STIFF
- 7 23.9 •••••• 6 LOOSE MEDIUM STIFF
- 9 ft 7 23.9 •••••• 6 LOOSE MEDIUM STIFF
- 10 34.2 ••••••••• 9 LOOSE STIFF
- 12 41.0 ••••••••••• 11 MEDIUM DENSE STIFF
- 3 m 10 ft 11 37.6 •••••••••• 10 LOOSE STIFF
- 12 36.7 •••••••••• 10 LOOSE STIFF
- 9 27.5 ••••••• 7 LOOSE MEDIUM STIFF
- 10 30.6 •••••••• 8 LOOSE MEDIUM STIFF
- 11 ft 14 42.8 •••••••••••• 12 MEDIUM DENSE S TIFF - 20 61.2 ••••••••••••••••• 17 MEDIUM DENSE VERY STIFF
- 21 64.3 •••••••••••••••••• 18 MEDIUM DENSE VERY STIFF - 12 ft 11 33.7 ••••••••• 9 LOOSE STIFF
- 14 42.8 •••••••••••• 12 MEDIUM DENSE STIFF
- 12 36.7 •••••••••• 10 LOOSE STIFF
- 4 m 13 ft 10 30.6 •••••••• 8 LOOSE MEDIUM STIFF
C:\My Documents\Wildcat\WC_XL97.XLS
HOLE #: T-4 WILDCAT DYNAMIC CONE LOG Page 2 of 2
PROJECT: Salvino Ct Landslide PROJECT NUMBER: 2200159
BLOWS RESISTANCE GRAPH OF CONE RESISTANCE T ESTED CONSISTENCY DEPTH PER 10 cm Kg/cm² 0 50 10 0 150 N' NON-COHESIVE COHESIVE - 9 24.9 ••••••• 7 LOOSE MEDIUM STIFF
- 9 24.9 ••••••• 7 LOOSE MEDIUM STIFF
- 14 ft 9 24.9 ••••••• 7 LOOSE MEDIUM STIFF
- 8 22.2 •••••• 6 LOOSE MEDIUM STIFF
- 8 22.2 •••••• 6 LOOSE MEDIUM STIFF
- 15 ft 10 27.7 •••••••• 7 LOOSE MEDIUM STIFF - 10 27.7 •••••••• 7 LOOSE MEDIUM STIFF
- 14 38.8 ••••••••••• 11 MEDIUM DENSE STIFF
- 16 ft 13 36.0 •••••••••• 10 LOOSE STIFF
- 5 m 11 30.5 •••••••• 8 LOOSE MEDIUM STIFF
- 13 33.0 ••••••••• 9 LOOSE STIFF
- 17 ft 14 35.6 •••••••••• 10 LOOSE STIFF
- 8 20.3 ••••• 5 LOOSE MEDIUM STIFF
- 10 25.4 ••••••• 7 LOOSE MEDIUM STIFF
- 18 ft 10 25.4 ••••••• 7 LOOSE MEDIUM STIFF - 10 25.4 ••••••• 7 LOOSE MEDIUM STIFF
- 11 27.9 •••••••• 7 LOOSE MEDIUM STIFF
- 19 ft 9 22.9 •••••• 6 LOOSE MEDIUM STIFF
- 10 25.4 ••••••• 7 LOOSE MEDIUM STIFF
- 6 m 17 43.2 •••••••••••• 12 MEDIUM DENSE STIFF
- 20 ft 21 48.9 •••••••••••••• 13 MEDIUM DENS E STIFF -
-
- 21 ft
-
-
- 22 ft
-
-
- 7 m 23 ft
-
-
- 24 ft
-
-
- 25 ft
-
-
- 26 ft
- 8 m
-
- 27 ft
-
-
- 28 ft
-
-
- 29 ft
-
- 9 m
C:\My Documents\Wildcat\WC_XL97.XLS
WILDCAT DYNAMIC CONE LOG Page 1 of 1
Questa Engineering Figure 6
1220 Brickyard Cove Road PROJECT NUMBER: 2200159
Richmond, CA 94801 DATE STARTED: 04-19-2023
DATE COMPLETED: 04-19-2023
HOLE #: T-5
CREW: MWF, SAF, CJG SURFACE ELEVATION: 159 (approx ft msl) PROJECT: Salvino Ct LS WATER ON COMPLETION: No GW
ADDRESS: 2929 Salvino Ct HAMMER WEIGHT: 35 lbs.
LOCATION: Richmond, Ca CONE AREA: 10 sq. cm
BLOWS RESISTANCE GRAPH OF CONE RESISTANCE TESTED CONSISTENCY Absolute Soil Description DEPTH
PER 10 cm
(4") Kg/cm² 0 50 100 150 N' NON-COHESIVE COHESIVE N' - 0 0.0 0 VERY LOOSE VERY SOFT 0
- 0 0.0 0 VERY LOOSE VERY SOFT 0
- 1 ft 0 0.0 0 VERY LOOSE VERY SOFT 0
- 1 4.4 • 1 VERY LOOSE VERY SOFT 1
- 0 0.0 0 VERY LOOSE VERY SOFT 0
- 2 ft 0 0.0 0 VERY LOOSE VERY SOFT 0
- 0 0.0 0 VERY LOOSE VERY SOFT 0
- 1 4.4 • 1 VERY LOOSE VERY SOFT 1
- 3 ft 0 0.0 0 VERY LOOSE VERY SOFT 0
- 1 m 6 26.6 ••••••• 7 LOOSE MEDIUM STIFF 7
- 6 23.2 •••••• 6 LOOSE MEDIUM STIFF 6
- 4 ft 7 27.0 ••••••• 7 LOOSE MEDIUM STIFF 7
- 8 30.9 •••••••• 8 LOOSE MEDIUM STIFF 8
- 7 27.0 ••••••• 7 LOOSE MEDIUM STIFF 7
- 5 ft 8 30.9 •••••••• 8 LOOSE MEDIUM STIFF 8
- 10 38.6 ••••••••••• 11 MEDIUM DENSE STIFF 11
- 13 50.2 •••••••••••••• 14 MEDIUM DENSE STIFF 14
- 6 ft 27 104.2 •••••••••••••••••••••••••••••• 25+ MEDIUM DENSE VERY STIFF 29 - 50 193.0 ••••••••••••••••••••••••••••••••••••••••••••••••••••••• 25+ VERY DENSE HARD 55 - 2 m
- 7 ft
-
-
- 8 ft
-
-
- 9 ft
-
-
- 3 m 10 ft
-
-
-
- 11 ft
-
-
- 12 ft
-
-
- 4 m 13 ft Claystone
Torvane, tsfSampler Type% Passing #200 SieveDry Density, pcfMoisture %Penetrometer, tsf Blows/Foot
Sample LocationGraphical SymbolUSCS Symbol
Lithologic Description
Groundwater Depth* (Converted to SPT N-value)Lab Tests
LOG OF SIDEWALL Figure
0 -1
-2
-3
-4
-5
-6
-7
-8
7 NW-1
2929 Salvino Ct at Santa Rita Road
Santa Rita Road, Richmond, CA
LL48
PL21
PI27
LL50
PL19
PI32
Grab
Grab
Grab
Grab
50 70
89 63
84 18
28 25
27 25
CL
CL
CL
CH
CH
CH
Sandy Clay: Dark Brown, moist, medium
stiff
Sandy Clay: Yellow Brown and Very Dark
Gray, medium stiff, moist
Sandy Clay: Very Dark Gray, medium stiff,
very moist
Fat Clay: Very Dark Gray, stiff, very
moist
Sandy Fat Clay: Very Dark Brown, stiff,
very moistFat Clay: Very Dark Brown, stiff, very
moist
UNIFIED SOIL CLASSIFICATION SYSTEM
AND KEY TO ABBREVIATIONS
FIGURE
GW
GP
GM
GC
SW
SP
SM
SC
ML
CL
OL
MH
CH
OH
Pt
Well graded Gravels, Gravel-Sand mixtures
Poorly graded Gravels, Gravel-Sand mixtures
Silty Gravels, poorly graded,
Gravel-Sand-Silt mixtures
Clayey Gravels, poorly graded
Gravel-Sand-Clay mixtures
Well graded Sands, Gravelly-Sands
Poorly graded Sands, Gravelly-Sands
Silty Sands, poorly graded, Sand-Silt mixtures
Clayey Sands, poorly graded,
Sand-Clay mixtures
Inorganic Silts and very fine Sands, rock
flour, Silty or Clayey fine Sands, or Clayey-Silts
with slight plasticity
Inorganic Silts, micaceous or diatomaceous
fine Sandy or Silty Soils,elastic Silts
Inorganic Clays of low to medium
Sandy Clays, Silty Clays,
lean Clays
plasticity,
Gravelly Clays,
Organic Clays and
of low
Organic Silty Clays
plasticity
Organic Clays of medium to high plasticity,
organic Silts
Inorganic Clays of high plasticity,
fat Clays
Peat and other highly organic soils
HIGHLY ORGANIC SOILS
SILTS AND CLAYS
LIQUID LIMIT GREATER THAN 50
SILTS AND CLAYS
LIQUID LIMIT LESS THAN 50
CLEAN GRAVELS WITH
LITTLE OR NO FINES
CLEAN SANDS WITH
LITTLE OR NO FINES
GRAVELS WITH
OVER 12% FINES
SANDS WITH
OVER 12% FINES
GRAVELS
MORE THAN HALF
COARSE FRACTION IS
LARGER THAN #4
SIEVE SIZE
SANDS
MORE THAN HALF
COARSE FRACTION IS
LARGER THAN #4
SIEVE SIZE
MAJOR DIVISION
FINE GRAINED SOILS
MORE THAN HALF IS SMALLER THAN
#200 SIEVE
COARSE GRAINED SOILS
MORE THAN HALF IS LARGER THAN
#200 SIEVE
TYPICAL NAMES
QE Cuesta ngineering orporation
P .O. Box 70356
1220 Brickyard Cove Road
Point Richmond, CA 94807
Phone: (510) 236-6114 FAX: (510) 236-2423
SOIL CLASS KEY.CDR
BOH
GRAB
Bottom of hole
LL, PL, PI Liquid Limit, Plastic Limit, Plasticity Index 6 8
Hand Sampling Equipment used to collect samples
0 10
20 30
40 50
60 0 10 20 30 40 50 60 70 80 90 100 110
Plasticity Index
Atterberg Limits
CL-ML
MH or OH
ML or OL
Symbol Liquid
Limit
Plastic
Limit
Plasticity
Index
48 21 27
50 19 31
9 Figure
Salvino Court/Santa Rita Road
2929 Salvino Court at Santa Rita Road, El Sobrante, CA
Atterberg Limits (ASTM D4318)
% Passing
#200 SieveClassification & Source
Yellow brown & dark gray sandy lean clay (CL), NW-1 1.5-4 ft Very dark brown fat clay/lean clay (CH-CL), NW-1 7-8 ft
70.1 83.8
0 10 20 30 40 50 60 70 80 90 100 110
Liquid Limit (LL)
0 10
20 30
40 50
60 70
80 90
100Percent Passing By Weight
Particle Size Analysis
Coarse Fine Coarse Medium Fine
Symbol
NW-1, 1.5-4'
10 Gravel Sand Silt Clay
FigureParticle Size Analysis
NW-1, 0.5-1.5'
Source
2929 Salvino Court
Salvino Ct at Santa Rita Road, El Sobrante, CA
0 10
0.0010.010.1110100
Particle Size in mm
0 10
20 30
40 50
60 70
80 90
100Percent Passing By Weight
Particle Size Analysis
Coarse Fine Coarse Medium Fine
Symbol
NW-1, 5-7'
NW-1, 7-8'
11 Gravel Sand Silt Clay
FigureParticle Size Analysis
NW-1, 4-5'
Source
2929 Salvino Court
Salvino Ct at Santa Rita Rd, El Sobrante, CA
0 10
0.0010.010.1110100
Particle Size in mm
LEGEND
DATE: 4/24/2023
PROJECT: Salvino Court
PROJECT NO.: 2200159
SOURCE: Map of landslide and other surficial deposits
of the Concord 15-minute
Quadrangle, Tor H. Nilsen (1973).
Site location =
Landslide Map
2929 Salvino Ct at Santa Rita Rd
El Sobrante, CA
F
IGURE
13 Landslide Map
at Santa Rita Rd
El Sobrante, CA