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Wellhead Protection

Wellhead Protection

Agriculture Weights and Measures Banner 750

  1. Except as provided in (b) below, the following activities shall be prohibited within 100 feet of a well (including domestic, municipal, agricultural, dry or drainage, monitoring, or abandoned wells):
    • mixing, loading, and storage of pesticides
    • rinsing of spray equipment or pesticide containers
    • maintenance of spray equipment that could result in spillage of pesticide residues on the soil
    • application of pre-emergent herbicides that are listed in 3CCR section 6800(a) or (b) (See reverse)
  2. Wells shall not be subject to the requirements when one of the following applies:
    • sited so that runoff water from irrigation or rainfall does not move from the perimeter of the wellhead toward the wellhead and contact or collect around any part of the wellhead including the concrete pad or foundation
    • protected by a berm constructed of any material sufficient to prevent movement of surface runoff water from the perimeter of the wellhead to the wellhead
      Note: Application of pre-emergent herbicides shall be prohibited between the berm and the wellhead

Examples of Berms

Even with Concrete Pad

Berm Even with Concrete Pad

Without Concrete Pad

Berm without Concrete Pad

Above Concrete Pad

Berm above Concrete Pad

Uphill from Wellhead

Berm uphill from Wellhead

Wellhead protection and pre-emergent herbicides

The wellhead protection regulation (California Code of Regulations (CCR) 6609) was added to protect wellheads from pesticide contamination. Among other provisions, this regulation prohibits application of pre-emergent herbicides within 100 feet of unprotected wells (those where water may flow from the area treated to the wellhead, and contact the wellhead). This prohibition was adopted because pre-emergent herbicides are the primary pesticides that have been found in ground water due to agricultural use.

Pre-emergent herbicides that have been found in ground water are both mobile and persistent, which are characteristic of pre-emergent pesticides listed in Title 3 CCR Section 6800(a) and (b) (the Ground Water Protection List). These herbicides are not allowed to be used within 100 feet of an unprotected well. However, some pre-emergent herbicides are not listed in 3CCR section 6800(a) or (b) because they are either not mobile or persistent. Because of this they are considered to have low potential to move offsite to ground water and are allowed to be used within 100 feet of an unprotected well.

For the purposes of the wellhead protection regulation, “pre-emergent herbicides” means pre-emergent herbicides that are listed in 3CCR section 6800(a) or (b):

Pre-emergent Herbicides on 6800(a) List
Atrazine, Simazine, Bromacil, Diuron, Prometon, Norflurazon

Esticides containing a chemical listed in title 3 ccr section 6800(a) when labeled for agricultural, outdoor institutional, or outdoor industrial are designated as restricted materials per title 3 ccr section 6400(d).

All purchases, statewide, must be made by a certified applicator.

All applications, statewide, must be made by or under the direct supervision of a certified applicator. Permits are generally required for restricted materials. However, no permit is required for use of a pesticide listed only in section 6400(d) when used outside of a ground water protection area (gwpa) or when used in a pest eradication program approved by the California department of food and agriculture.


Pre-emergent Herbicides on 6800(b) List (Examples of trade names are in bold)

  • Alachlor Intrro, Micro-tech
  • Aminocyclopyrachlor
  • Aminocyclopyrachlor Pottasium Salt
  • Aminocyclopyrachlor Tripropolamine Salt
  • Bensulfuron methyl Duet, Lordax
  • Bensulide Prefar
  • Chloropicrin
  • Chlorsulfuron Telar, Landmark
  • Clomazone Cerano
  • Cycloate Ro-Neet
  • Dazomet Basamid
  • Dichlobenil Casoron, Image
  • Diflufenzopyr, sodium salt Distict, Status
  • Dimethenamid-P Freehand, Outlook
  • Dithiopyr Dimension
  • EPTC Eptam, Eradicane
  • Ethofumesate BNB, Ethotron, Norton
  • Flazasulfuron
  • Halosulfuron-methyl Sandea, Yukon
  • Hexazinone Velpar
  • Imazamox, ammonium salt Beyond, Raptor
  • Imazapyr, isopropylamine salt
  • Imazethapyr, ammonium salt Pursuit
  • Isoxaben Gallery
  • Linuron Lorox
  • Mesotrione
  • Metolachlor Drexel, Parallet, Stalwart
  • (S)-Metolachlor Brawl, Medal, Dual, Bicep
  • Metribuzin Metri, Sencor, Tricor
  • Napropamide Devrinol
  • Oryzalin Surflan
  • Prometryn Caparol
  • Propyzamide Kerb
  • Pyrazon Pyramin
  • Rimsulfuron Matrix
  • Siduron
  • Sulfentrazone
  • Sulfometuron-methyl Oust, Landmark
  • Thiencarbazone-methyl
  • Thiobencarb Bolero
  • Triallate

Examples of pre-emergent herbicide active ingredients not listed in Title 3 CCR section 6800(a) and (b) that are allowed to be used within 100 feet of an unprotected well include:

  • Oxyfluorfen Goal
  • Pendimethalin Pendulum, Prowl
  • Prodiamine Barricide
  • Flumioxazin Chateau, Payload