Park West CC(18)-CS 891005 TRENCH EXCAVATION DESIGN
OCTOBER 5~ 1989
PARK WEST COMMERCE CENTER
SITE 1
STORM DRAINS
DONALD E. DAVIS
CONSULTING ENGINEERS
5506 COCKRELL HILL ROAD
DALLAS, TEXAS 75236
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THIS INVESTIGATION WAS CONDUCTED TO DETERMINE THE GEOTECHINiCAL ENGINEERSING
CHARACTERISTICS OF THE SUBSURFACE PROFILE AT THE PURPOSED LOCATION FOR THE
STORM DRAIN LINE AS SHOWN ON THE DRAWINGS. THE SUBSURFACE CONDITIONS WERE
EVALUATED iN ORDER TO FORMULATE RECOMENDATIONS FOR EXCAVATIONS OF OPEN CUT
TRENCHES FOR THE STORM DRAIN AT THIS SITE.
THE TEST BORINGS ARE SHOWN IN THE GEOTECHNICAL INVESTIGATION BY MASON .JOHNSTON
AND ASSOCIATES, iNC. FOR "PARK WEST COMMERCE CENTER - SITE 1", DATED 23 JUNE,
198~. THESE TEST BORINGS WERE USED IN THE EVALUATION FOR OPEN CUT TRENCHES
THAT WILL BE USED IN THE STORM DRAIN.
RECOMMENDATIONS:
TRENCH METHODS - SEVERAL TRENCHING METHODS ARE AVAILABLE TO THE UTILITY
CONTRACTOR INCLUDING OPEN CUT SLOPED EXCAVATION, SPACED SHEETING, TRENCH BOXES
AND SHORINO. THE SCOPE OF THIS REPORT DOES NOT INCLUDE SPECIFICATIONS FOR
SHORING OR TRENCH BOXES. PURPOSED SHORNING OR TRENCH BOX DESIGN MUST BE
SUBMITTED AND APPROVED PRIOR TO USE ON THIS .JOB SITE.
SLOPES FOR TRENCHING AND EXCAVATIONS - THERE ARE TWO SOILS TYPES FOUND IN THE
SUBSURFACE PROFILE AT THIS SITE, AND EACH SOIL WILL BE CUT AT A DIFFERENT
ALLOWABLE SLOPE. THE FOLLOWING TABLE OUTLINES THE DIFFERENT SOIL TYPES WITH
THE ALLOWABLE CUT SLOPES FOR OPEN TRENCHES.
TYPE DECRIPTION STEEPEST ALLOWABLE SLOPE
HORIZONTAL : VERTICAL
DEPTH 0-12 FT DEPTH 12-20 FT
C CLAY~ STIFF DARK BROWN 1 : 1 2 : I
A CLAY, STIFF LIGHT BROWN 3/4 : 1 1 : I
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PRECAUTIONS:
IF THERE IS ANY INDICATION OF GENERAL OR LOCAL INSTABILITY, SLOPES SHOULD BE
CUT BACK AT LEAST 1/4 HORIZONTAL TO 1 VERTICAL FLATTER THAN THE STABLE SLOPE.
TRENCHES 0-12 FEET WILL OPEN LESS THAN 18 HOURS. iF OPEN LONGER THAN 18 HOURS,
USE THE i2-20 FEET VALUES FOR CUT SLOPE.
SOIL BENEATH THE WATER TABLE IS NOT INCLUDED IN THIS REPORT. IF THE WATER
TABLE IS ENCOUNTERED USE BOX TYPE SUPPORT.
TRENCHS WITH TWO OR MORE SOIL TYPES SHOULD BE CLASSIFIED IN ACCORDANCE WiTH
THE WEAKEST LAYER.
INSPECTION: DAILEY INSPECTION OF ALL EXCAVATIONS SHALL BE MADE BY A REGISTERED
PROFESSIONAL ENGINEER, WITH PERIODIC INSPECTIONS BY A REPRESENTATIVE OF THE
GEOTECHNICAL ENGINEER. ALL OSHA RECOMMENDATIONS ARE TO BE FOLLOWED BY THE
CONTRACTOR .
THESE RECOMMENDATIONS ARE BASED ON THE GEOTECHNICAL REPORT. HOWEVER. IT MUST
BE RECOGNIZED THAT THE CONCLUSIONS REACHED IN THIS REPORT WERE BASED ON THE
CONDITIONS AT THE TEST BORING LOCATIONS. THESE FINDINGS WERE OBTAINED, AND
THESE RECOMMENDATIONS PREPARED IN ACCORDIANCE WITH GENERALY ACCEPTED
ENGINEERING PRINCIPLES AND PRACTICES. SHOULD ANY UNUSUAL CONDITIONS BE
ENCOUNTERED DURING CONSTRUCTION, THiS OFFICE IS TO BE NOTIFIED IMMEDIATELY SO
THAT FURTHER iNVESTIGATIONS CAN BE MADE.
CONS,..'LTING ENGINEER