Soil Boring and Groundwater Monitoring

Most commercial facilities and some permitted pits, such as brine pits, will require soil borings as part of the permit application, and may require installation of groundwater monitoring wells if shallow groundwater is present within 100 feet below ground.

Soil borings must be drilled at the proposed location to characterize the subsurface. Detailed soil boring logs will be used as part of the application to determine whether additional liners or containment will be necessary in the waste management units, and in calculating the Closure Cost Estimate, to determine whether soils excavated from the site would be appropriate backfill or capping material. The number of borings must be representative of the total number of acres for the site.

If groundwater is not observed during drilling, the soil boring should be advanced to 100 feet. Borings should be left open for a minimum of 24 hours to determine if groundwater is present. If shallow groundwater is present at the site (within 100 feet below ground surface), a minimum of three groundwater monitoring wells will be required. Wells should be spaced around the facility or pit, close to the facility operational area, with at least two wells on the estimated down-gradient side of the operational area. Additional wells may be required for larger facilities.

Note that soil boring logs and potentiometric surface maps are considered geologic work products and must prepared under seal of a registered Professional Geologist (P.G.), as required by the Occupations Code Chapter 1002.

Prior to installing groundwater monitoring wells, submit a “Soil Boring and Groundwater Monitoring Plan” as part of your application, to ensure that the placement of the wells will be approved.

  1. The following is required for each soil boring or groundwater monitoring well drilled:
  • The wells must be completed by a certified water well driller in accordance with 16 TAC Part 4, Chapter 76 (Water Well Drillers and Water Well Pump Installers).
  • The wells must be completed to penetrate the shallowest groundwater zone, and the completion must isolate that zone from any deeper groundwater zone.
  • The screened interval of the wells must be designed to intercept at least 5 feet of groundwater. The well screen must extend above the static water level.
  • Provisions must be made to protect the well heads from damage by vehicles and heavy equipment.
  • The wells must be maintained in good condition with a lockable watertight expansion cap.
  • The following information must be submitted after the new wells are completed:
    • A soil boring lithological log for the well, with the soils described using the Unified Soil Classification System (USCS) (equivalent to ASTM D 2487 and ASTM D 2488). The log must also include the method of drilling, well specifications, slotted screen type and slot size, riser and screen length, bentonite and cement intervals, total depth, and the depth of the first encountered groundwater or saturated soils. The sand pack size should be compatible with the well screen slot size, as well as the local lithology.
    • A well installation diagram, detailing construction specifications for each well
    • A survey elevation for each well head reference point (top of casing) relative to a real or arbitrary on-site benchmark relative to mean sea level
    • A table with recorded depth to water, top of casing, and adjusted depth to water data
    • An updated Site Plan and a potentiometric surface map showing static water levels, the calculated gradient, and the estimated direction of groundwater flow
  1. The groundwater monitor wells must be able to provide a sample that is representative of the groundwater underlying the site for the duration of facility operations. If a monitor well is not capable of providing a representative sample, the permittee must notify Technical Permitting in Austin and install a replacement monitor well that is acceptable to the RRC. Additional groundwater monitoring wells may be required with future site development.
  2. All monitor wells must be monitored and/or sampled for the following parameters after installation, and quarterly thereafter:

    PARAMETER

    UNITS

    Static Water Level

    Feet (ft)

    Total Depth

    ft

    pH
        EPA Method 150.1, 150.2, or equivalent

    s.u.

    Total Dissolved Solids (TDS)
        EPA Method 2540C or equivalent

    mg/L

    Total Petroleum Hydrocarbon (TPH)
        Method TX1005

    mg/L

    Benzene
        EPA Method 602 or equivalent

    mg/L

    Soluble Cations:
      Calcium, Magnesium, Potassium, and Sodium
        EPA Method 6010/6020 or equivalent

    mg/L

    Soluble Anions:
      Bromides, Carbonates, Chlorides, Nitrates, and Sulfates   
        EPA Method 300/9056 or equivalent

    mg/L

  1. All chemical laboratory analyses required to be performed in accordance with this permit must be performed using appropriate Environmental Protection Agency (EPA) methods or Standard Methods by an independent, National Environmental Laboratory Accreditation Program (NELAP) certified laboratory neither owned nor operated by the permittee. Any sample collected for laboratory analysis must be collected and preserved in a manner appropriate for that analytical method as specified by 40 CFR, Part 136.
  2. If any of the parameters listed show potential impacts from operations at the facility, or if a liner system failure as defined under permit occurs, Technical Permitting reserves the authority to initiate an appropriate sampling frequency.
  3. All groundwater monitoring wells must remain operational, and monitoring requirements must continue as specified in permit until written approval from Technical Permitting in Austin is granted for plugging and abandoning the wells.

 



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