Wellhead Protection

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)
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 Without Concrete Pad

Above Concrete Pad 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: