Department of Health Seal

TGM for the Implementation of the Hawai'i State Contingency Plan
Section 5.1


A site visit is imperative to evaluate conditions that might influence the design and implementation of the Sampling and Analysis Plan. Historic site information and data are compiled and reviewed during the first and second steps of Systematic Planning of the site investigation (see Section 3). This information is used to identify potential areas of concern and designate initial DU areas for sample collection.

Finalization of the location, area, and depth of final DUs is carried out during the site visit. Logistical needs to carry out sampling are then assessed, including necessary access agreements, the need to remove equipment, debris and/or vegetation prior to sample collection, presence of pavement that may require drilling, presence of subsurface utilities, soil conditions, and optimal tools for sample collection and related details. These topics are discussed in detail in the following sections.


Designation of Decision Units (DUs) for characterization is an important part of the initial site investigation process (see Section 3). Decision Unit locations are based on the site history and known or suspect areas of contamination.

Once established, the boundaries of final DUs should be marked using flagging, paint or similar means. A to-scale map of the DU locations and boundaries is an important component of the site investigation report. This allows the investigated area to be relocated in the future if needed. Simple sketch maps are not acceptable. The dimensions of the DU should be carefully measured and recorded, with key corners and boundaries georeferenced or surveyed. The approximate area of the DU should be determined and recorded. This information will also be required to help establish the spacing of increments within the DU for sample collection (see Section 4.2.4). Use of a data sheet or data log is strongly encouraged to ensure that essential information regarding the selected DUs is documented for the site investigation report (see Figure 5-47).


Assess the type and compactness of soil within potential DU areas during the initial site visit. Bring tools to test the type and compaction of the soils and potential presence of shallow rocks or buried debris, for example a sampling tube and a small pick. Different tools are required for the collection of samples from different soil types. For example, sampling tubes are appropriate for soft fine-grained soils, while sampling tubes with slide hammers or battery-powered hammer drills with spade bits might be required for compacted or hard soils. In most cases multiple types of tools should be taken to the field to ensure that samples can be collected should unforeseen circumstances arise.

Areas of gravel, asphalt or other materials covering DUs targeted for sampling should be noted. The need to remove or dig or drill through this material should be included in site planning. Vehicles, debris, or other material within DUs that will need to be moved for access should be discussed with the property owner. Clearing of grass and weeds to improve access and expedite sample collection might be required in some areas. It is important to remember that data representing the mean contaminant concentration for DUs are only valid if systematic random increment locations in the DUs are accessible for sampling. Any substantial areas of a site that are not accessible to locate planned systematic random increments (e.g. former building foundation pads or paved/graveled roadways that cannot be drilled through, clusters of dense vegetation that cannot be cleared or accessed for sampling, etc.) should be identified/mapped as data gaps and documented in the site investigation report.

Look for the potential presence of shallow subsurface utilities or other features that might interfere with surface (or subsurface) soil sample collection. For example check for potential irrigation lines in landscaped areas or obviously well-watered lawns or shallow electrical conduits attached to sidewalk lighting. Look for sprinkler heads and water piping or electrical conduits extending from buildings or outside air conditioning units, water heaters, etc.

Note the presence of overhead utilities, trees or structures that might interfere with access of field equipment. For example low, overhead utilities or structures might require the use of a smaller track-mounted push rig for the collection of subsurface samples. General precautions for overhead clearance are given in Occupational Safety and Health Administration (OSHA) guidance on Cranes and Derricks in 29 CFR 1926.550(a)(15), but these should be regarded as bare minimums. Provide photographs and/or videos to the drill operator if they will not able to visit the site prior to the initiation of field work.


If the collection of subsurface soils is to take place then the presence of buried utilities or other features should be noted during the initial site evaluation. Look for direct surface connections and other indirect potential indicators of subsurface utilities and features. These indicators might manifest themselves in various ways:

  • Prior subsurface location surveys – Worksites often have multiple stages of construction or other site work that involve their own subsurface surveys. It is not uncommon to find markings from prior surveys indicating subsurface utilities or features. Examples of these markings include surface paint marks, stakes, pins and small, wire flags.
  • Direct attachments to subsurface utilities – These are the surface segments directly attached to subsurface utilities or features. This includes manholes, valve pits, valves, standpipes, hose bibs and hydrants.
  • Irregularities in surface or surface cover – These are caused by or associated with but not directly attached to subsurface utilities or features. Example of these are: linear cuts in concrete/asphalt cover, linear depressions, raised surfaces, sharply defined lack of vegetation, patches or other irregularities in surface cover that suggest a definable feature.

Have a plan to modify boring and increment locations due to unanticipated underground utilities or other defined obstacles. These impediments to sample collection should be included in the site investigation report discussed in Section 3.9.

A review of existing information should also be carried out to assess soil types likely to be encountered in the subsurface, as well as the anticipated depth to groundwater. Direct push rigs are preferable for the collection of continuous cores and subsurface Multi Increment samples. Other methods might be required for very dense or rocky soils or for drilling through bedrock.