HomeMy WebLinkAboutCE 83-21; CALAVERA HILLS SUBDIVISION; STORMDRAIN CUTOFF WALLS; 1986-09-30SOUTHERN CALIF"ORNIA SOIL AND TESTING, INC.
6280 RIVERDALE ST. SAN DIEGO, CALIF. 92120 • TELE 280-4321 • P.O. BOX 20627 SAN DIEGO, CALIF". 92120
7 4 - B :3 1 VEL lEW A Y PAL MOE S E R T, CAL I 1'". ';l 2 2 6 0 • TEL. E :3 46-1 0 7 B
6 7 BEN T E R P R I S EST. ESC 0 N 0 I 0 0, CAL. I 1'". ';l 2 0 2 S • TEL. E 7 4 6 .4 S 4 4
September 30, 1986
Pacific Scenes, Inc.
3900 Harney Street
San Diego, California 92110
ATTENTION: Mr. Bob Fontana
SCS&T 8421000
Report No. 34
SUBJECT: Stormdrain Cutoff Walls, Calaveras Hills Subdivision, Harwich
Drive, Carlsbad, California.
REFERENCE: Letter by Southern California Soil and Testing, Inc., regarding
Stormdrain Cutoff Walls, Calaveras Hills Subdivision, Carlsbad,
California, dated September 23, 1986.
Gentlemen:
This report has been prepared at your request to further address the lack
of cutoff walls for three stormdrains which were constructed at the subject
site. The referenced report addressed the erosion characteristic of the
soil s and presented the opinion that the cutoff wall s were not necessary
due to possible erosion of the backfill material. We now understand that
the City Engineering Department would like our opinion in regards to the
need for this cutoff walls to stabilize the pipe for lateral forces caused
by flow within the pipe.
Lateral forces in pipes are generally caused by changes in direction of the
pipe where unbalanced internal pressure can occur. The stormdrain pipe are
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" SCS&T 8421000 September 30, 1986 Page 2
not pressure vessel s and therefore shoul d not be subject to very 1 arge
forces resulting from this condition. Where changes in vertical direction
occur, all three pipes have catch basins that provide support for any such
unba 1 anced forces. Two of the s tormdra ins have no change in hori zonta 1
di recti on. The thi rd pi pe, located between Lots 265 and 222, has a
relatively sl ight horizontal curve where it extends down a slope. (Radius
equals 150 feet) However, where this curve occurs, the pipe trench is in
natural ground, which in that area is metavolcanic rock and very dense
soils .produced by weathered metavo.1canic rock. This material has a very
high lateral load capacity and should provide more than adequate support
for the pipe. Since no other horizontal curves exist in the pipe, no other
areas are expected to experience any lateral loading.
Based on the above we conclude that the backfill soils, structural fill
materials and the native soils are all capable of providing adequate
support for the three stormdrains without the cutoff walls. Therefore, it
is our opinion that the cutoff walls are not necessary in this case.
If you should have any questions after reviewing this report, please do not
hesitate to contact this office.
This opportunity to be of professional service is sincerely appreciated.
Respectfully submitted,
SOUTHERN CALIFORNIA SOIL & TESTING, INC.
ei-R-II~~
Charles H. Chri~tian, R.C.E. #22330
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cc: (4) SUbmitted
(2) Rick Engineering
(1) SCS&T, Escondido