Dry Wells

Dry wells are commonly used for storm and run off water on commercial and residential properties.   When a dry well receives storm water it purpose is to allow the waters to percolate into the subsurface soils well above the regional aquifer.

Dry wells are required to be registered in the State of Arizona and are regulated by the ADEQ under the Aquifer protection program (APP). Paradise Septic Drilling can assist

Dry Well Registration Assistance
All persons who own an existing dry well or who plan to install a dry well are required to register the dry well with the Arizona Department of Environmental Quality (ADEQ).   Dry wells are also required to be registered prior to decommissioning.  EN TECH® can assist dry well owners in the registration procedures.

Percolation Testing and Subsurface Characterization
Effective storm water management requires an understanding of drainage patterns and subsurface permeability for percolation of storm water disposal.  It is also important to direct storm water away from areas where chemicals are used, transferred or stored that could contaminate the water.  EN TECH®‘s geologists and engineers provide site drainage evaluations and design.  Percolation tests are performed on subsurface soils to evaluate soil permeabilities and capacity of the soils to absorb storm water disposal from dry wells.  These studies assist in the effective design of storm water management systems.

Design and Installation
Dry well designs incorporate several factors including:

  • the anticipated volume of storm water
  • the drainage area feeding the dry well
  • information on historical precipitation events
  • characteristics of the drainage surfaces (e.g. concrete, asphalt, grass, dirt)
  • the types and distribution of subsurface soils
  • the permeability and storage capacity of the subsurface soils
  • the depth and local use of groundwater
  • site usage and chemical storage

EN TECH® evaluates these factors in determining the need for retention basins, pretreatment equipment and designing the number, location, size, depth and sediment handling capacity of the dry wells.  The ADEQ requires dry wells be installed by a licensed dry well driller.  EN TECH® works closely with several licensed drillers in the specification and installation of dry wells.

Aquifer Protection Permit – Determination of Applicability
Dry wells may be regulated under the Aquifer Protection Permit (APP) program of the ADEQ when they are in areas where hazardous materials are used, stored, loaded or treated or when they receive discharges other than storm water (e.g. industrial wastewater injection wells).  The determination as to whether a dry well is regulated under this program rests with the ADEQ.  The ADEQ may supply the dry well owner with a Determination of Applicability form to be completed for their review in determining if an APP is required.   EN TECH® assists our clients in the collection of data and preparation of the determination of applicability form.

Aquifer Protection Permit Application and Regulatory Liaison Services
The APP requirements apply to dry wells that drain areas where hazardous substances are used, stored, loaded or treated.  The APP is used to ensure that best management practices are followed and that no hazardous substances enter the dry well.  The ADEQ may require dry well owners apply for an APP after review of the determination of applicability form.

Best Management Practices Plan (BMPP)
The APP may require that the dry well owner develop a Best Management Practices Plan (BMPP) in order to minimize the possibility of contaminating soil, groundwater or surface water from contaminated runoff.  This plan is typically only applicable to industrial or commercial properties that use, store, load or treat hazardous substances.   Discharge of any contaminant resulting in a violation of the Aquifer Water Quality Standard (AWQS) is prohibited by State law.

Some factors to consider in developing a BMPP include:

  • Types of hazardous substances present and how they are used
  • Exterior and interior locations of storage, use and/or treatment areas
  • Site drainage patterns
  • Spill containment structures
  • Spill response procedures; containment, cleanup and waste disposal
  • Waste management and housekeeping procedures including containerization, waste minimization and recycling/reuse
  • Dry well maintenance practices
  • Employee training; chemical handling, spill response and waste disposal
  • Pretreatment and alternative discharge options

Investigations and Sampling
If a dry well owner suspects contamination or is directed by the ADEQ to perform an investigation of the dry well, EN TECH® can develop and implement a dry well investigation to evaluate the presence and extent of contamination.  EN TECH®‘s investigation procedures are designed to address the concerns of the ADEQ while being cost-effective to our clients.  The ADEQ may require an investigation of a dry well prior to abandonment.  The investigation process is summarized in the Dry well Investigative Screening Process Chart and may involve some or all of the following:

  • Collection and analysis of sediment samples from the dry well settling chamber
  • Background information on dry well construction, pretreatment, subsurface soils, surface water, groundwater depth and flow direction

If sample results are above ADEQ guidance levels for dry well sediment samples, additional investigations may be required including the following:

  • Settling chamber clean out
  • Drilling an investigative soil boring adjacent to the dry well, log the soil profile, collect soil samples and determine the vertical extent of soil contamination, if any
  • Analyze soil samples for contaminants of concern and compare with Groundwater Protection Levels (GPLs)

If soil samples collected from the soil boring exceed the GPLs, a groundwater investigation may be required after evaluation of the vertical extent of soil contamination and the depth to groundwater.  Soil and/or groundwater remediation may be required if contamination is present above regulatory levels.

Abandonment and Clean Closure
EN TECH® can assist the dry well owner in the proper registration notification, investigation and abandonment procedures for dry well decommissioning.  Clean closures do not require an APP permit.  However, a dry well investigation may be required prior to closure to satisfy clean closure requirements.