HomeMy WebLinkAboutCT 2018-0003; MAGNOLIA BRADY; PRELIMINARY PERMEABLE PAVEMENT RECOMMENDATIONS; 2018-05-21GEOCON
INCORPORATED
GEOTECHNICA
Project No. G2l92-52-01
May21,2018
Ashton 3, LLC
5 Hoya Street
Rancho Mission Viejo, California 92694
Attention: Mr. Taylor Ashton
REC ·l_ f''ED
OCT O 2 2019
LAND DEVELUPMf::NT
ENGINEE!~ING
Subject: PRELIMINARY PERMEABLE PAVEMENT RECOMMENDATIONS
1534 MAGNOLIA A VENUE
CARLSBAD, CALIFORNIA
References: 1. Geotechnical Investigation, 1534 Magnolia Avenue, Carlsbad, California, prepared
by Geocon Inc., dated January 17, 2017 (Project No. G2l92-52-01 ).
2. Preliminary Grading Plan for: "Magnolia-Brady", 1534 Magnolia Avenue,
Carlsbad, California, prepared by Civil Landworks, dated March 28, 2018.
Dear Mr. Ashton:
In accordance with the request of Mr. Dave Lother, we prepared this letter to provide additional
pavement recommendations for the subject project. We understand that pervious pavement and
permeable pavers are being considered from a storm water management perspective for the driveways
at the site.
Recommendations provided herein are based on an assumed R-Value of 44 for the subgrade materials
and a Traffic Index (TI) of 4.0 and 5.0 for light vehicle loading (pedestrian) and driveways,
respectively. The final pavement sections should be based on the R-Value of the subgrade soil
encountered at final subgrade elevation.
PERMEABLE INTERLOCKING PAVER PAVEMENT
We calculated the paver pavement sections in general conformance with the Ca/trans Method of
Flexible Pavement Design (Highway Design Manual, Section 608.4) and the Interlocking Concrete
Pavement Institute (ICPI) Tech Spec Number 18. We calculated the section based on an assumed
minimum R-Value of 44 and 78 for the subgrade soil and permeable base/stone materials,
respectively. We used an equivalent asphalt concrete section equal to the thickness of the pavers of
approximately 3 inches in accordance with Interlocking Concrete Pavement Institute (ICPI) Tech Spec
Number 4. In addition, the pavers should be installed in a pattern appropriate for vehicular traffic. The
pavers should possess a minimum thickness of 3 ½-inches and overlie 1-to l ½ inches of bedding sand,
ASTM No. 8 stone or per the manufacturer's recommendations. Table 1 presents the recommended
permeable paver pavement section.
6960 Flanders Drive ■ Son Diego, California 92121 -2974 ■ Telephone 858.558.6900 ■ Fox 858.558.6159
TABLE 1
PERMEABLE PAVER PAVEMENT SECTION
Minimum Estimated Option I Option 2
Base and Estim ated Bedding Traffic Stone Paver Permeable Location Index (Tl) Reservoir Thickness Coarse Class 2 Base ASTM C33 Thickness Material (inches) (inches) Thickness Aggregate
R-Value (Inches)
Light vehicle 4.0 78 3½ I to I ½ 5 4" #57 I
loading (pedestrian) 3" #2
Private driveways 5.0 78 3½ I to I ½ 6 4" #57 I
4" #2
The base/aggregate sections can be thickened to increase the water capacity as required by the project
civil engineer. Prior to placing base materials, the subgrade soil should be scarified, moisture
conditioned as necessary, and recompacted to a dry density of at least 95 percent of the laboratory
maximum dry density near to slightly above optimum moisture content as determined by ASTM
D 1557. The depth of compaction should be at least 12 inches. Similarly, the base materials should be
compacted to a dry density of at least 95 percent of the laboratory maximum dry density near to
slightly above optimum moisture content.
The pavers should be installed and maintained in accordance with the manufacturer's
recommendations. The future owners should be made aware and responsible for the maintenance
program. In addition, pavers tend to shift vertically and horizontally during the life of the pavement
and should be expected. The pavers normally require a concrete border to prevent lateral movement
from traffic. The concrete border surroundin g the pavers should be embedded at least 6 in ches into the
subgrade to reduce the potential for water migration to the adjacent landscape areas and pavement
areas. The pavers should be placed tightly adjacent to each other and the spacing between the paver
units should be filled with appropriate filler.
PERVIOUS CONCRETE PAVEMENT RECOMMENDATIONS
The design thickness of the pervious concrete pavement should have a minimum thickness as
presented in Table 2.
TABLE 2
PERVIOUS CONCRETE PAVEMENT RECOMMENDATIONS
Location Portland Cement Concrete (inches)
Private Driveways (TC=A) 5.0
The pervious concrete pavement should be underlain by a minimum 4 inches of open-graded (I-inch
maximum size) aggregate or class 2 permeable base compacted to a dry density of at least 95 percent of
the laboratory maximum dry density. The base/aggregate sections can be thickened to increase the water
capacity as required by the project civil engineer. Prior to placing base/aggregate materials, the subgrade
soil should be scarified, moisture conditioned as necessary and recompacted to a dry density of at least
95 percent of the laboratory maximum dry density near to slightly above optimum moisture content as
determined by ASTM D 1557. The depth of compaction should be at least 12 inches. Base materials
Project No. G2 I 92-52-0 I -2 -May 21 , 2018
.,
should be compacted to a dry density of at least 95 percent of the laboratory maximum dry density near
to slightly above optimum moisture content. Compactive effort should be applied during the placement
of the underlying aggregate section.
PERMEABLE/PERVIOUS PAVEMENT DRAINAGE AND SETBACKS
In areas where permeable/pervious pavement is planned, the subgrade materials should be graded to
provide positive drainage into a subdrain and controlled drainage device. The subdrain should be
placed at the bottom of the pavement section along the low point of the roadway/driveway to reduce
the potential for water to build up within the paving section. The drain should be connected to an
approved drainage device. Where a concrete border is not used, impermeable liners should be installed
along the sides of the pavement section to prevent lateral water migration. The liner should consist of a
high-density polyethylene (HDPE) or equivalent with a minimum thickness of 15 mil and should be
installed such that the liner is not punctured. The liner should be sealed at the connections in
accordance with manufacturer recommendations and should be properly waterproofed at the drain
connection. The drain should consist of a 3-inch diameter perforated Schedule 40, PVC pipe and
placed at the bottom of the base or aggregate materials.
The permeable/pervious pavement should be located at least 5 feet from the planned structures.
Footings located adjacent to the permeable/pervious pavement will need to be deepened below a 1: 1
projection from 1 foot below the pavement section bottom.
Should you have any questions regarding this report, or ifwe may be of further service, please contact
the undersigned at your convenience.
Very truly yours,
GEOCON IN CORPORA TED
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GE 2714
MRL:SFW:dmc
(e-mail) Addressee
Project No. G2 l 92-52-0 I -3 -May21,2018