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Water Well Construction Related Wastewater and General Permit #6

Iowa DNR Wastewater General Permit #6 (GP6) for Well Construction and Well Service Discharges was renewed on July 1, 2023 and is effective through June 30, 2028. Click here to download General Permit #6.

Questions regarding General Permit #6 can be directed to:

Wendy Hieb, Iowa DNR NPDES Wastewater Section, by phone at 515-808-3039, or by email at


Erik Day, Water Supply Engineering Section, by phone at 515-725-0237, or by email at

GP6 Well Siting ToolImage and link for the GP6 Well Siting Atlas

The Iowa DNR developed an online GP6 Well Siting Tool to assist landowners, well contractors, and engineers.

The tool is useful for performing desk evaluations of well sites and help determine if the well location will likely require discharge management through GP6. It also helps define which locations likely cannot support well construction discharge due to close proximity of Outstanding Iowa Waters (OIWs).

As a user of this tool, you have access to map layers that will help you identify distances to surface waters and OIWs, locations of sinkholes, karst areas, land slope, and more. It also allows you to print the map you create to use as a resource.

The GP6 Well Siting Tool works with Google Chrome and Mozilla Firefox web browsers. Currently, it is not compatible with Internet Explorer. To open and use the GP6 Well Siting Tool, click on the following link:

To learn more about GP6 and the resources available to help you comply, click on the following link:

The GP portion of GP6 is an abbreviation of the term General Permit. The number 6 is the order in which the General Permit was developed by DNR - in this case, GP6 is the sixth of nine General Permits developed by the department

General permits are developed and used by the DNR when the type and quality of wastewater generated by an activity is similar, regardless of where in the state the activity takes place.

The characteristics of well construction discharge wastewater meets this criteria. This type of discharge normally consists of groundwater mixed with coarse and fine geologic materials like clay, silt, sand, and bedrock fragments. During the drilling process, there may be limited quantities of drill fluid enhancement products used to stabilize the borehole walls and carry borehole cuttings to the ground surface.

General Permit 6 (GP6) is a statewide discharge permit that authorizes the discharge of water well related wastewater into Waters of the United States as long as the wastewater meets the general water quality standards. Discharges under GP6 are temporary and limited only for the time that water well related services are taking place.

Meeting the general water quality standards can be achieved by using one or more "best management practices" - also known as BMPs - to slow, retain, and filter the wastewater, and allow the geologic materials contained within the wastewater to settle out before the treated water reaches a Water of the United States.

If the well related wastewater will not reach a Water of the United States, you do not need to meet the requirements of GP6.

Well contractors approached the State Legislature seeking a uniform and defined rule that authorized discharge of well construction wastewater from well construction sites.

In response to this request, The 82nd State General Assembly passed a statute which required the Department to write new rules and a develop a General Permit to authorize well construction and well services related wastewater discharge when that discharge reaches a Water of the United States. The Bill History can be found at the following web link:

The department worked with well industry professionals from our state to develop General Permit #6, as well as guidance documents to help inform contractors and engineers on how to meet the conditions of the new requirements.

Starting on March 17, 2010, all well construction, well related service, and GHEX loop borehole drilling related wastewater that reaches a Water of the United States is regulated by National Pollution Discharge Elimination System permit (NPDES) General Permit #6 (GP6).

Many well construction sites are located near ditches, waterways, or subsurface drainage inlets that may allow well construction related wastewater to reach a Water of the United States.

Well construction related wastewater normally consists of groundwater mixed with coarse and fine geologic materials like clay, silt, sand, and bedrock fragments. It can also contain limited quantities of drilling fluid enhancement products designed for use in drinking water wells. The fluid enhancement products help stabilize the well's borehole and help the well contractor successfully complete the well.

When allowed to flow untreated, the wastewater may eventually reach a stream, river or a lake. This can result in turbidity that can affect aquatic life and deposit sediments that create undesirable changes to the stream or lake bed.

In addition, when released in large quantity, drilling fluid additives and other products used in drilling and servicing wells may contain substances that are acutely toxic to aquatic life. These products can chemically and physically alter the water body and cause additional problems like killing aquatic life and inhibiting the life processes for all species that depend on the water.

Untreated discharges also impact the manner in which the water is used or enjoyed by adjoining property owners and citizens who have access to the water. The photos below illustrate what happens when well construction discharge enters a stream.

Well construction discharge at the point of stream entry.
Well construction discharge after mixing - downstream several hundred feet.
Well discharge near stream entry point. Well discharge after mixing downstream.

Water well construction wastewater is the wastewater generated by any of the water well drilling related activities in our state. The wastewater from these activities can be made up of drilling fluids, groundwater, or a combination of both. In can also contain geologic materials and chemicals used to enhance drilling. It can be very turbid to nearly clear.

If the well drilling related activities create discharges that reach Waters of the United States, it falls under the category of GP6 controlled wastewater which requires the site to follow the conditions set by GP6. The following activities commonly fall under GP6.

  • New water well construction;
  • existing water well rehabilitation and renovation;
  • water well pump installation;
  • water well test pumping and capacity testing;
  • geothermal heat exchange borehole drilling;
  • groundwater observation and monitoring well construction for sites that will not generate contaminated water;
  • water well test hole drilling;
  • water well test well construction; and.
  • potentially other types of drilling that access or utilize the groundwater for a specific purpose, fall under the definition of "well" or water well" in Iowa rules, and discharges well construction related wastewater into Waters of the United States.

Anytime the wastewater generated by well related construction and services is discharged off the well construction site and reaches a Water of the United States, the wastewater falls under the requirements of GP6. GP6 requires the discharger to comply with certain treatment standards and discharge requirements. If the well construction or well services related wastewater does not reach a Water of the United States, the discharge is not subject to GP6.

The following services are not covered under GP6:

  • The actual production pumping and on-going operation of dewatering wells. Dewatering discharge is now managed under General Permit #9 - please see the information on dewatering found on the General Permit #9 webpage.
  • The construction of oil and gas test wells and production wells - please contact the Iowa DNR staff listed at the bottom of the page for more information on these discharges.
  • The discharge of wastewater from gas reservoir production or injection wells.
  • Recreational well pumping and discharge into a water feature.
  • Horizontal drilling associated with underground utility work.
  • And any other discharge that is not directly associated with construction, reconstruction, rehabilitation, or service/repair of water supply well, geothermal borehole systems, test boreholes or test wells, or uncontaminated groundwater monitoring and observation wells..

First, determine if the well construction wastewater will leave the well construction site and reach a Water of the United States. If the answer is yes, then you are legally obligated to follow the requirements of GP6. If the answer is no - your water will not reach a Water of the United States - then you do not need to follow GP6 (but you still need to manage your discharge responsibly).

For all discharges that require GP6, you are required to create a well water pollution prevention plan (also known as a WWPPP, pronounced "wip") for the site before any discharge to Waters of the United States takes place. The WWPPP that you create will be the water treatment model you assemble and use to control and treat the wastewater that is generated during your well services.

The WWPPP shall take into account items that will influence how the wastewater is managed, such as:

  • The location of the well on the landscape;
  • the potential protections or limitations that the landscape may provide for natural wastewater treatment;
  • the potential quantities and anticipated qualities of wastewater that may be generated during each phase of the well construction or service work;
  • the types, quantities, and locations of best management practices (BMPs) used both on and off of the construction site to hold, filter and treat, and meter the wastewater before it enters Waters of the United States;
  • any adjustments or changes made to the BMPs after the initial installation;
  • who inspects the BMPs, how often the inspections are performed, and what is found during the inspections;
  • determine if you have co-permittees that need to be part of your WWPPP and have them sign-on with your WWPPP as a co-permittee;
  • provide a Field Office Notification Form (also known as FON, pronounced "fawn") to the local DNR Field Services Office up to 5 days before the planned discharge, but no later than 24 hours after the discharge starts.

During the times that you discharge, you must:

  • inspect your BMPs at least once every six hours to make sure they are adequate for the discharge you generate,
  • inspect the receiving body of water and determine if your BMPs are adequate, if not, add additional BMPs to further refine the wastewater treatment, and
  • document your inspection on an inspection form as proof that you are monitoring the discharge and that you are taking the necessary steps to meet the conditions of GP6.

If you find that any of the BMPs are inadequate and that the discharge is in violation of Iowa's "general water quality" parameters, you must take corrective action immediately. This includes stopping the discharge until you can increase the BMPs and improve water treatment, and notify the Iowa DNR.

All issues and comments about your discharge, WWPPP, co-permittees, or inspections, should be recorded on your inspection form. You are also required to update your WWPPP to reflect the additional BMPs. After addressing the water quality issue(s), you can resume the discharge, monitor the BMPs and discharge water quality, and follow-up with additional inspections.

For more details on the requirements, please review our guidance document titled "A brief Guide to Developing a Well Water Pollution Prevention Plan and Using Best Management Practices"

Not all Waters of the United States can be used as a discharge point by following the conditions of GP6. Iowa has a class of waters called "Outstanding Iowa Waters" or "OIWs" that require the discharger to apply for and obtain an individual National Pollutant Discharge Elimination System (NPDES) Discharge Permit through Iowa DNR before any discharge can take place.

Outstanding Iowa Waters are streams/stream segments or lakes that have been designated as high quality waters that constitute an outstanding resource to our state and its citizens. These waters are such an exceptional recreational or ecological significance that the water quality of these features shall be strictly maintained and protected.

Iowa DNR has a map of Outstanding Iowa Waters that will help you locate the areas of the state that have more stringent permitting and discharge requirements.

You can also use the new GP6 Well Siting Tool to determine if the area where the planned well will be constructed in in an area that includes one or more of the Outstanding Iowa Waters. Click on the following link to view the tool - GP6 Well Siting Tool.

For more information on Outstanding Iowa Waters, please visit the following page:

If your discharge will reach an OIW, or you have questions about applying for an Individual NPDES Discharge Permit, please contact Wendy Hieb for more information. Wendy can be reached by phone at 515-725-8405 or by email at

You should contact your local IDNR Field Services office if you suspect a body of water is being impacted by well construction or well service related discharges.

Iowa DNR Regional Field Office Contact Information


Map of Iowa DNR Field Offices and assigned numbers

Field Office 1 - NE Iowa
1101 Commercial Court, Suite 10
Manchester, IA 52057
P: 563-927-2640
F: 563-927-2075

Field Office 2 - NC Iowa
2300 15th St. SW
Mason City, Iowa 50401
P: 641-424-4073
F: 641-424-9342

Field Office 3 - NW Iowa
1900 N. Grand Ave., Ste. E17
Spencer, Iowa 51301
P: 712-262-4177
F: 712-262-2901

Field Office 4 - SW Iowa
1401 Sunnyside Ln.
Atlantic, Iowa 50022
P: 712-243-1934
F: 712-243-6251

Field Office 5 - SC Iowa
Wallace State Office Building
502 East 9th Street
Des Moines, Iowa 50319
P: 515-725-0268
F: 515-725-0218

Field Office 6 - SE Iowa
1023 W. Madison
Washington, Iowa 52353
P: 319-653-2135
F: 319-653-2856

For more information about GP6 and how you can comply, please contact:

Erik Day - phone: 515-725-0237,
Iowa DNR Water Supply Engineering, 502 E 9th Street, Des Moines, IA 50319, or by Fax: 515-725-8202.


Wendy Hieb - phone: 515-808-3039,
Iowa DNR NPDES Wastewater Permits, 502 E 9th Street, Des Moines, IA 50319, or by Fax: 515-725-8202.