HomeMy WebLinkAboutOC_RS041332 - Soils (2)SCOTT AND PAULA BOWERS April 27, 2004
J.N. 185-04
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Proposed GradinE
The enclosed preliminary grading plan, Plate 1, indicates that cuts of approximately 11
to 17 feet are proposed to reach planned finish pad grades within the limits of the
subterranean garage and basement. Proposed grading within the front yard area
includes cuts of a few tenths up to approximately 5 feet and fills of up to 1 foot.
Grading along the side yards includes cuts of a few tenths up to approximately 14 feet
(within the ramped driveway area). Cuts and fills ranging up to approximately 3 feet
are planned within the backyard; however, locally deeper cuts will be required in the
area of the swimming pool and spa. The depths of these cuts will depend on the actual
depths of the pool and spa that are not shown on the grading plan.
The preliminary grading plan, Plate 1, also indicates that grading will be performed to
modify the outer edges of the southern and western sides of the building pad. These
modifications will consist of cuts and fills of 2 feet or less.
It is expected that a drainage system will be designed for the site to collect surface
runoff and direct it to the existing area drain inlet located at the southwesterly corner of
the lot. It is expected that this drainage system will consist of area drains, earth swales
and sheet flow gradients in landscape areas, and sloped concrete flatwork.
Furthermore, grate drains are anticipated across the ramped driveway and across the
entrance to the subterranean garage. The ramped driveway, subterranean garage and
basement areas are expected to drain to a storm drain lift station. It is expected that
water collected in the storm drain lift station will be pumped through a force main to
the existing area drain located at the southwestern comer of the site. It is also expected
that the subdrains behind the proposed onsite retaining walls will also flow into the
proposed storm drain lift station.
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SCOTT AND PAULA BOWERS April 27, 2004
J.N. 185-04
r Page 7
r SITE RECONNAISSANCE AND SUBSURFACE EXPLORATION
A site reconnaissance was performed by a representative of this firm on March 11,
2004 (on the same day that we performed our subsurface exploration). Our
reconnaissance consisted of the visual evaluation of the building pad and adjacent
slopes. Existing surface conditions within the site and surrounding areas, as observed
during our site reconnaissance, were described previously in the "Site Location and
Description" section of this report.
Our subsurface exploration involved the drilling of two exploratory borings with a
bucket -auger drill rig to depths of 31 and 41 feet below existing ground surfaces.
Earth materials encountered were visually classified and logged in accordance with the
Unified Soil Classification System. The approximate locations of the exploratory
borings are shown on the enclosed preliminary grading plan, Plate 1, and descriptive
"Exploration Logs" of the borings are presented in Appendix A.
Associated with our subsurface exploration was the collection of bulk and relatively
undisturbed samples of artificial fill and terrace deposits for laboratory testing. The
undisturbed samples were obtained using a 3 -inch, outside diameter, modified
California split -spoon soil sampler lined with 1 -inch -high brass ring liners. The
central portion of the driven core samples were placed in sealed containers and
transported to our laboratory for testing.
LABORATORY TESTING
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To evaluate the engineering properties of site soils, several laboratory tests were
performed on selected samples of fill and terrace deposits considered representative of
those encountered. Laboratory tests included the determination of maximum dry
density, expansion potential, soluble sulfate content, pH, resistivity and Atterberg
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SCOTT AND PAULA BOWERS April 27, 2004
J.N. 185-04
Page 45
Pool Decking
Pool decking should be constructed in accordance with the recommendations presented
in the "Exterior Concrete Flatwork" section of this report.
Plumbing Fixtures
Leakage from the swimming pool or from any of the appurtenant plumbing could
create adverse saturated conditions of the surrounding subgrade soils. Localized areas
of oversaturation can lead to differential expansion (heave) of the subgrade soils and
subsequent raising and shifting of concrete flatwork. Therefore, it is essential that all
plumbing and pool fixtures be absolutely leak -free. For similar reasons, drainage from
pool deck areas should be directed to local area drains and/or graded earth swales
designed to carry runoff water to a suitable discharge point.
Exterior Concrete Flatwork
Thickness and Joint Spacing
To reduce the potential of unsightly cracking related to the effects of moderately
expansive soils, concrete sidewalks, and patio -type slabs should be at least 4 inches
thick and provided with construction joints or expansion joints every 6 feet or less.
Concrete subslabs to be covered with decorative pavers should also be at least 4 inches
thick and provided with construction joints or expansion joints every 6 feet or less.
New concrete driveway slabs, if any, should be at least 5 inches thick and provided
with construction joints or expansion joints every 10 feet or less.
Reinforcement
Consideration should be given to reinforcing all concrete patio -type slabs, pool
decking, driveways and sidewalks greater than 5 feet in width with No. 3 bars spaced
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SCOTT AND PAULA BOWERS April 27, 2004
J.N. 185-04
Page 50
This opportunity to be of service is sincerely appreciated. Please call if you have any
questions pertaining to this report.
Respectfully submitted,
P�ETRRA GEOTECHNICAL, INC.
Daniel Orris
Staff Geologist
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Senior Project Engineer
RCE 56591
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Darrel Roberts
Principal Geologist
CEG 1972
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No. C 56591
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