Phase II Environmental Site Assessments 

If a Phase I ESA determines that further assessment is required, or there is certainty of environmental impact, a Phase II ESA will be developed that will further evaluate the nature and extent of those impacts via subsurface and groundwater investigations. Aztech’s team of geologists, drillers and environmental technicians are experienced and capable of handling the tasks required for the successful completion of Phase II ESAs.

Our in-house equipment includes three drill rigs that give us the ability to conduct soil probing and sampling, in addition to drilling via hollow stem auger and other rotary methods, in locations ranging from limited access and/or low clearance to locations of unrestricted access.

Subsurface Soil Investigation

Aztech geologists are talented, thorough and well versed in conducting soil investigations that range from advancing soil borings in shallow and/or deep overburden to bedrock coring. The scope of the subsurface soil investigation is developed based on the findings of the Phase I ESA or from other existing information relative to the site to be investigated. The goal is to determine if any environmental impacts to the subsurface soils exist at the site.

Aztech geologists and drillers collaborate to advance soil borings to depths sufficient to spatially and vertically evaluate the soil quality down to the top of bedrock, if necessary. Depending on the nature of the soil materials present beneath a site, soil borings are typically advanced using either a track or truck‐mounted, hydraulic drill rig using either direct‐push probing methods with macrocore sampling or split spoon sampling. Depth‐discrete soil samples are collected and the soil samples are examined in the field for grain size, color, odor (if present) and moisture content. Each soil sample is placed in an airtight container and the headspace is screened in the field using a photoionization detector (PID) calibrated to a standard isobutylene calibrant gas.

In many cases, the soil sample from each soil boring location exhibiting the highest PID reading in the headspace is submitted to an approved laboratory for analysis of the contaminant of concern (COC). Typically, in the absence of PID readings or other evidence of COCs in the soil headspace, the soil sample collected from the soil/water interface is submitted for laboratory analysis. Drill logs containing pertinent information, such as the geotechnical qualities and classification of soils, the location of the soil water interface and, the depth interval of the soil sample analyzed by the laboratory, are kept for each respective borehole.  The soil characteristics and analytical data obtained from each borehole tell a story. Aztech geologists evaluate these data and are able to determine the presence and concentration of COCs, the depth and lateral distribution of COCs and, the pathway in which the COC has traveled through the various soil types. This information allows us to identify, define and delineate the area in the subsurface in need of remedial activities and develop a remedial approach specific to the COC and, the job site.

Groundwater Investigation and Monitoring

During drilling activities, temporary or permanent monitoring wells can be installed to assess the quality of groundwater on a job site. An Aztech geologist will log the geotechnical data associated with the site soil and identify the position of the water table during advancement of the borehole. Based on the observations made during drilling, the geologist will develop specifications for and oversee the construction of the monitoring well.  Typically, soil borings are converted into 2.0‐inch inside diameter (ID) or 4.0‐inch ID schedule 40 PVC monitoring wells that are constructed in a manner that is consistent with industry standards.

After completing the monitoring well installation, the top of the well casing elevation is determined at each location and is generally tied to a site datum of 100.00 feet. The purpose of establishing the top of casing elevations to the site datum is to collect subsequent depth to water measurements from each monitoring well so that groundwater elevations at each location can be determined and the direction of groundwater flow beneath the site can be evaluated.  After the depth to water measurements are obtained, groundwater samples are collected from the newly installed monitoring wells, using disposable bailers, in order to evaluate the groundwater quality beneath the site. The groundwater samples are analyzed for COCs suspected at the site in accordance with state and federal regulations.
The data obtained during the field activities is compiled into a comprehensive draft Phase II ESA report that summarizes the field methods, observations, and analytical results for soil and groundwater sampling. The draft Phase II ESA report will also provide recommendations regarding future work at the site. This can include recommendations for additional soil borings and/or monitoring wells and can establish a frequency for subsequent groundwater sampling events. These recommendations can also be used to develop remedial alternatives for a site, if warranted. After the draft report is completed, it is sent to the client for review and comment. The Phase II ESA report is subsequently finalized.