Report/subsurface exploration/geotechnical review

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• EXPLORATTON/CLASSIFICATION METHODS SAivfPLING METHODS Split-Spoon Samples (SS} - Calibrated to N�Values Standard peneuaaon(split-spoon)samples were collected in general accordance with ASTM:D 1586 with one primary modificacion_ The ASTM tesc method consists of driving a 2" O.D. spiit-barrel sampler in[o the in-situ soil with a 140-pound hammer dropped from a height of 30". The sampler 'rs driven a to�al of 18" into the soil. Afcer an ini[ial set of 6", the number of hammer blows co drive the sampler the final 12" is known as the scandard penetration resiscance or N-vaIue. Our method uses a modified hammer wei�ht. which is determined by measuring the syscem ener;y using a Pile Driving Analyzer (PDA) and an instrumented rod. In the past, standard pene[ra�ion N-value tests were performed usine a rope and cathead for the Iift and drop sys[em. The ener�y cransf�erred to the spli�-spoon sampler was rypically lirni[ed to about 60% ot it's poten[ial enerey due to the friction inheren�in this system. This convened energy then provides what is known as an N�blow count. Most of todays drill rigs incorporate an automatic hammer lift and drop system, which has higher energy efficiency and subseq�encly results in tower N-values than the traditional N� values. By using the PDA euergy measurement equipment, we are able to determine actual energy eenerated by the drop hammer. With the various hammer systems available, we have found highly variabte energies ranging from 55% to over 100%. Tt�erefore, the intent of AET's hammer calibrations is to vary the hammer weieht such that hammer energies lie within about 60% to 65% of the theore[ical ener;y of a 140-pound weight falling 30". The current ASTM procedure acknowledees the wide variation in N-values,sta[ing that N-values of 100%or more have been observed. Althoueh we have noc yet decemuned the scatistical measurement uncertainry of our calibrated method to date, we can sca�e that the accuracy devia[ion of the N-values using this method are significandy hetter than the standard ASTM Method. Disturbed Samples (DS)lSpin-up Samples (Sin Sample rypes described as "DS" or "SU" on the boring logs are disturbed samples, which are taken from the flights of the auger. Because the auger dismrbs the samples, possible soil layering and contact depths should be considered approxunate_ Sampling Limitations Untess actually observed in a sample, contacts between soil layers are estimated based on the spacing of samples and the action of drilling tools.Cobbles, boulders, and other large objects generally cannot be recovered from test borings, and they may be presenc in the ground even if they are not noted on the baring (ogs. CLASSIFICATION 1VfETAODS Soil ciassifica[ions s6own on the boring logs are based on the Unified Soil Classification (USC) system. The USC system is described in ASTM:D2487 and D2488. Where laboratory classificaaon tests (sieve analysis or Atterberg Limits} have been performed, accurate classifica[ions per ASTM:D2487 are possibie. Otherwise, soil classifications shawn on the boring logs are visual-manuai judgments. Charts are attached which provide information on the USC system, the descaptive ter.ninology, and the symbols used on the boring Iogs. ' The boring logs inciude descriptions of apparent geology.The geologic depositional origin of each soil layer is interpreted primarily by ohservatian of the soil samples, which can be 1'united. Ohservations of the surrounding topography,vegetation,and deveiopment can somecunes aid this judgment. WATER LEVEL MEASUREMENTS The ground water level measurements are shown a[the bottom of the boring logs.The foilowing informadon appears under "Wa[er Level Measuremencs" on the logs: • Date and Tune of ineasurement � S2TT1Pled Dep[h: lowest depth of soif sampling ac rhe time of ineasurement • C3SiIIg Depth: dep[h co bottom of casing or hollow-stem auger at nme of ineasuremenc • C3ve-iI1 DePih: dep[h a[which measuring npe scops in t6e borehole • Watei I.2ve1: dep�h in che borehole where free waeer is encaun�ered • Drilling Fluid Level: same az Waier L.evei,except that rhe liguid in the barehole is driltiag fluid The true location of the water table at the boring locations may be different than the water levels measured in the boreholes. This is possible because there are several factors that can affect the water level measurements in the borehole. Some of these factors include: permeability of each saii tayer in profile, presence of perched water, amount of tune between water Ievel readinas, presence of dritling fluid, weather condi[ions, and use of borehole casing. v SAMPLE STORAGE Unless notified to do otherwise, we routinely retain representative samples of the soils recovered from the borings for a period of 30 days. OIREPOSIC(9/03) AMERICAN ENGINEERING TESTING, INC.