Excavation pit

Significant releases of petroleum hydrocarbons from unlined surface impoundments in oil fields have also been reported as far back as the early 1900s. One unlined surface oil reservoir located in the Kem River field, southern California, had a reported fluid loss on the order of 500,000 barrels. Excavated pits showed oil penetration to depths exceeding 20 ft. Another loss of 1 million barrels over a period of 6 years occurred from another unlined reservoir in the same field, although some of this loss was through evaporation. 

Systematic sampling on a two-dimensional grid is used for characterizing large areas of surface soil floors and walls of excavation pits and trenches and for the verification of decontaminated surfaces cleanup. An example of a systematic sampling... 

We use sampling grids mainly for surface soil sampling, however, it is not unusual to place soil borings and collect subsurface samples on a grid pattern. Grids are also used for soil sampling from the bottom and sidewalls of excavation pits and trenches. 

In the course of remediation projects we often need to sample from the bottom and sidewalls of excavation pits. A variation of excavation pit sampling is sampling from test pits and trenches. Test pits are small excavations usually made with a backhoe for a purpose of collecting a subsurface soil sample. A trench is a long and narrow excavation originating from a pipeline removal or placed with earth moving equipment for exploratory purposes. 

Overlaying a grid system over a deep excavation pit may not be always possible. In this case, we need to delineate a regularly shaped area around the pit and to mentally project a grid system over the pit as illustrated in Figure 3.9. 

To overlay a sampling grid over an excavation pit, we follow these steps ... 

Fig. 21. Horizontal plan of the rock shelter no. 1 of Uppony. A. side passage with sediments of layers 2-5 B. side chamber with sediments of layers 13 and 14 C. the excavation pit of 1963, which cut into layers 6-12. Hatching indicates the location of the remaining material from layer no. 1.

Large burial sites Pueblo, Colo. Tooele/Deseret Chemical Depot, Utah Suspected to contain buried M70 bombs in burn/burial pits Approx. 25 pits where CWM bombs and 4.2-in. mortars were burned and buried Site will be closed under Base Realignment and Closure Many CWM munitions at this site are expected to be empty due to burn/burial process 1. Excavate pits (using appropriate methods, either manual or robotic) 2. Identify potential CWM as it is uncovered 3. Assess potential CWM using x-ray and portable isotopic neutron spectroscopy 4. Dispose of CWM in appropriate system(s) staged at the site... 

The use of the class 4 dredged material site has made possible the removal of the heavily contaminated silt which is found in specific localities in the harbours and fairways of the estuary. In the first phase, sections of the Petroleum Harbour were dredged to the required depth and the material was deposited in previously excavated pits in the Botlek Harbour. Specific conditions were laid down to cover the methods... 

Field test are carried out in the excavated pits or boreholes at the required depths. The results reflect the mass characteristics of the ground as well as overcome disturbance effects of samples retrieved for laboratory tests. Common field tests carried out to assess strength, compressibility and seepage parameters are as presented in Table 3.5 (Canadian Geotechnical Society 1987). Typical equipment for pressuremeter test and test setup for plate bearing test are shown in Figures 3.6 and 3.7 respectively. 

Computer-aided detection and assessment becomes a sensible solution, where surface disturbances have been removed or are non-existent, and deeply buried anomalies are assumed. This is usually the case in excavation pits and in open areas. 

Lower levels means areas beiow the ievei where the empioyee is iocated and to which an empioyee can faii. Such areas inciude, but are not iimited to, ground ieveis, fioors, roofs, ramps, runways, excavations, pits, tanks, ma-teriais, water, and equipment. 

Lower levels means those areas or surfaces to which an employee can fall. Such areas or surfaces include, but are not limited to, ground levels, floors, platforms, ramps, runways, excavations, pits, tanks, material, water, equipment, structures, or portions thereof. 

When piles are being driven in an excavated pit, the walls of the pit shall be sloped to the angle of repose or sheet-piled and braced. 

It is recommended that the pipe be inspected for damage at every excavation pit as it being pulled back and after the installation is complete... 

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