none, Geotechnical review of grading, CorrespondenceWILLDAN
Serving Public Agencies
13200 Brooks Drive, Unit 0
Baldwin Park, California 91706
626/337-5103 fax 626/337-2103
www.wiIIdan.com
December 21, 2000 via fax and mail
Mr. Craig R. Nealis
City Manager
City of Rolling Hills
2 Portuguese Bend Road
Rolling Hills, California 90274
Subject: GEOTECHNICAL REVIEW OF
COUNCIL REGULATIONS
AND GRADING PLANS
4 Ringbit Road West, Lot 8-A-SF
6 Ringbit Road West, Lot 8-A-2-SF
Rolling Hills, California
INTRODUCTION
This presents our geotechnical review of documents regarding grading at 4 and 6
Ringbit Road West in Rolling Hills, California. The purpose of this review is to
evaluate the documents and determine if the completed grading is in substantial
conformance with approved grading plans and Council resolutions. This work
was performed in accordance with our proposal dated 11/30/00 and your written
authorization. Documents reviewed are summarized below:
1. Rolling Hills City Council, 3/9/98, Resolution No. 835, A Resolution of the City
Council of the City of Rolling Hills Granting Site Plan Review Approval for the
Construction of a New Single Family Residence in Zoning Case No. 545A.
2. Rolling Hills City Council, 2/28/00, Resolution No. 876, A Resolution of the
City Council of the City of Rolling Hills Granting Site Plan Review to Permit
Grading to Develop a Driveway and a Retaining Wall for Ingress and Egress
to an Adjacent Property in Zoning Case No. 603.
3. Bolton Engineering Corp., 8/19/99 (revised 12/9/99), Revised Access Portion
of Lots 1 & 2, Tract 30074, Rolling Hills, Scale 1" = 20', Job No. 98203, 1
Sheet.
4. Bolton Engineering Corp., 3/5/98, Grading Plan Portion of Lots 1 & 2, Tract
30074, Rolling Hills, Scale 1" = 20', Job No. 98206, 1 Sheet.
5. Bolton Engineering Corp., 10/17/00, As Built Grading Plan GR 11200002, #6
Ringbit Road West, Rolling Hills, CA, 90274, Portions of Lot 1 and 2, Tract
30074, Scale 1" = 20', Job No. 98206, 1 Sheet.
December 21, 2000 Geotechnical Review of Grading
Page 2
6. Bolton Engineering Corp., 12/14/00, Grading Sequence, #4 & #6 Ringbit,
Rolling Hills, CA, BEC File No. 98206.
7. Keith W. Ehlert, 11/10/00, As -Graded Geologic Report for Proposed
Residential Development #6 Ringbit Road West, Rolling Hills, California,
Project No. 3203-OOAG.
8. SWN Soiltech Consultants, Inc., 10/20/00, Compaction Report Proposed
Residential Development, Lot 2, Tract 30074,. 6 Ringbit Road West, Rolling
Hills, California, Project Ref. 3879-00.
As part of this work we also visited the site, discussed site conditions and grading
operations with representatives of Bolton Engineering, and discussed the project
with you.
BACKGROUND
The project includes two Tots and two grading projects. The same person owns
both lots and the projects are interrelated. The first project is 6 Ringbit Road
West (Lot 8-A-2-SF). Grading at 6 Ringbit included cut and fill to develop a level
building pad for a single family residential structure. Reference 1 is a City Council
Resolution approving the project. Reference 1, Section 11, Items D, E, J, K, and
S regulate grading operations. Applicable portions are paraphrased below:
D. The lot shall be developed and maintained in substantial
conformance with the approved site plan (Reference 4).
E. Grading quantities shall not exceed 2,170 cubic yards cut and
2,170 cubic yards fill.
J. The 15-foot wide access road/driveway shall conform to L.A.
County Fire Department requirements for width and gradient.
K. Grading shall preserve existing topography, flora, and natural
resources to the extent possible.
S. An as -built grading plan shall be prepared by a civil engineer
showing the project was graded in conformance with the
development plan with a building pad height of 882 feet
(Reference 5).
The second project is 4 Ringbit Road West (Lot 8-A-SF). Grading at 4 Ringbit
included cut and fill to develop an access road/driveway in conformance with
Item J from Reference 1. Reference 2 is a City Council Resolution approving the
December 21, 2000 Geotechnical Review of Grading
Page 3
project. Reference 2, Section 7, Items D, E, J, L, and S regulate grading
operations. Applicable portions are paraphrased below:
D. The lot shall be developed and maintained in substantial
conformance with the approved site plan (Reference 3).
E. Grading quantities shall not exceed 970 cubic yards cut and 970
cubic yards fill.
J. The access road/driveway shall be 15 feet wide and gradually
widen to 20 feet near property line. The access road/driveway
shall conform to L.A. County Fire Code.
L. Grading shall preserve existing topography, flora, and natural
resources to the extent possible.
S. An as -built grading plan shall be prepared by a civil engineer
showing the project was graded in conformance with the
development plan.
We understand the same contractor completed grading on both projects. Grading
started with grubbing and site preparation for placement of fill on 6 Ringbit. Next,
cuts were made for the access road/driveway on 4 and 6 Ringbit. These cuts
included roadway widening, roadway realignment, and excavation of a backcut
for stabilization fill. Spoil from the cuts was placed as engineered compacted fill
to form a level building pad on 6 Ringbit. The total quantity was about 915 yards.
Cuts were then made on 6 Ringbit for two stabilization fills. Spoil was partly
stockpiled on 6 Ringbit and placed as stabilization fill in the two backcuts. This
quantity was about 2,000 yards cut and 2,000 yards fill. Finally, an excavation
was made for the basement of the structure which resulted in about 965 yards of
spoil which was placed as stabilization fill on 4 Ringbit. About 50 yards remain for
backfill of the basement excavation after construction.
CONCLUSIONS
We evaluated the references provided, visited the site, and discussed site
conditions with the project engineer. Based on our review, we believe the grading
completed on 4 and 6 Ringbit is in substantial conformance with the approved
grading plans and Council Resolutions. Based on information available for this
review, earthwork on 6 Ringbit apparently did not excced 2,170 yards cut or
2,170 yards fill. Earthwork on 4 Ringbit likewise did not exceed 970 yards cut or
970 yards fill.
• -f
December 21, 2000 Geotechnical Review of Grading
Page 4
Grading operations extended across the property line between 4 and 6 Ringbit
creating one construction project from two grading plans and project approvals.
Based on our review of References 1 and 2, this was not specifically authorized
or prohibited by Council Resolution. The decision to do this was made by the
contractor during construction to improve the efficiency and decrease the cost of
earthwork. Though grading operations extended across the property line
between 4 and 6 Ringbit, the total yards of earthwork and the proposed ground
contours were not significantly changed from the approved plans on either
project. The building pad elevation on 6 Ringbit is 882 feet according to the as -
built grading plan and grade check stakes on site. Survey control came from off
site elevation points on Ringbit road.
CLOSURE
This review was performed in accordance with generally accepted professional
engineering geology principles and practice in Southern California at this time.
We make no other warranty, either express or implied. Comments presented
herein are based on review of work by others. No field exploration or laboratory
testing was performed. Please contact us if you have questions or need
additional services.
ectfully submitted,
WILLDA
S. Santo, CEG 1866
President
Manager Geotechnical Division
Dist: 2/Addressee