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Note that the borehole dataset contains multiple tables. It is important to understand what is (and is not) included with this data set. Accordingly, please review the descriptive files before beginning to use the data. Also, we address below some of the issues that one should be aware of when using these data. We have compiled existing borehole data from the files of cities, counties and other public agencies. We cannot vouch for the accuracy or precision of any of the data because we did not participate in the initial fieldwork involved in its generation. Nevertheless, we have strived to select for our files only those logs with adequate documentation and of sufficient quality that we judge are appropriate for use in our mapping efforts.
We attempt to capture the data and compile them in our database in a way that represents, as closely as possible, what is shown on the boring logs and presented in the reports that accompany them. However, a range of individuals, from licensed, experienced geologists on our staff to relatively inexperienced student assistants, has been involved in entering the data into our database. It is likely that all of these individuals did not follow exactly the same procedures (no matter how well defined) during data entry. Naturally, because not all drilling-rig operators and on-site geologists or engineers use industry standard descriptions or techniques, we have been forced, at times, to try to translate nonstandard data and nomenclature to standard, or consistent, nomenclature and values.
Variations in our methods of locating borings and estimating the elevation of the ground surface where the boring was made depend upon several factors. These include: the type of maps presented in the report; the documentation in the report and on the log; the terrain information available in our GIS; and the vintage of the map we use to locate the boring. In some cases, the best available topographic maps that we use to locate borings and estimate elevations predate changes due to local development and grading.
Difficulty in discerning from the log and associated report all of the parameters used in making the boring is very common. Occasionally, we have been required to make deductions and assumptions about how the borings were advanced.
A few parameters (for example, dry density) can be recorded exactly as presented on the log or on the associated laboratory data sheets. Alternatively, because not all labs and firms report parameters the same way, we may translate the data to a different form for recording in our database.
Soil descriptions are taken verbatim from the logs/reports. However, in a very few cases we have had to supplement or correct apparent errors in descriptions or classifications that were omitted from the original log or incorrectly reported.
We hope that you are successful in using these data. Feel free to contact us with questions or comments.