TGW Public Notification!

Trout Gulch Mutual Water Co. operates three wells. TGW shows manganese in excess of the listed secondary maximum contaminant level (SMCL) in water produced from the new well, Well #3 at 90 Victoria Lane. Well #1 on Norman Road also exceeds the MCL.  However, water from Well #1 is not being used for distribution. Well #1 remains in stand-by mode currently. Well #2 is below the SMCL.

                Contaminant        Secondary Standard (maximum contaminant level - SMCL)

                 Manganese (Mn)                                0.05 mg/L (or 50 parts per billion)

Check the web chart for current levels in TGW water from Well #3.

Manganese is a naturally-occurring element that can be found ubiquitously in the air,

soil, and water.

Manganese is an essential nutrient for humans and animals.   (Leach and

Harris, 1997; U.S. EPA, 2003a).  Adverse health effects can be caused by inadequate intake or

over- exposure (See a review by Keen et al., 1999 and Keen et al., 2000).  The main exposure of

Humans to manganese are from ingestion of food. Manganese deficiency in humans appears to be

rare because manganese is present in many common foods. Manganese is essential to the proper

Functioning of both humans and other animals as it is required by many cellular enzymes (e.g.

manganese superoxide dismutase, pyruvate carboxylase) and can serve to activate many others

(e.g., kinases, decarboxylases, transferases, hydrolases, etc.; Hurley et al., 1984; Wedler, 1994;

WHO, 2002).  


Although manganese is an essential nutrient at low doses, chronic exposure to high doses

may be harmful. There are substantial data supporting the neurological effects of inhaled

manganese in both humans and animals, however, there are little data for the association

between oral exposure to manganese and toxic effects.

EPA has established National Secondary Drinking Water Regulations that set non-mandatory water quality standards for 15 contaminants. EPA does not enforce these "secondary maximum contaminant levels" or "SMCLs." They are established only as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color and odor. These contaminants are not considered to present a risk to human health at the SMCL.

Table I. Secondary Maximum Contaminant Levels


Secondary MCL

Noticeable Effects above the  Secondary MCL


0.05 to 0.2 mg/L*

colored water


250 mg/L

salty taste


15 color units

visible tint


1.0 mg/L

metallic taste; blue-green staining



metallic taste; corroded pipes/ fixtures staining


2.0 mg/L

tooth discoloration

Foaming agents

0.5 mg/L

frothy, cloudy; bitter taste; odor


0.3 mg/L

rusty color; sediment; metallic taste; reddish or orange staining

Manganese (Mn)

0.05 mg/L

black to brown color; black staining; bitter metallic taste


3 TON (threshold odor number)

"rotten-egg", musty or chemical smell


6.5 - 8.5

low pH: bitter metallic taste; corrosion 
high pH:
 slippery feel; soda taste; deposits


0.1 mg/L

skin discoloration; graying of the white part of the eye


250 mg/L

salty taste

Total Dissolved Solids (TDS)

500 mg/L

hardness; deposits; colored water; staining; salty taste


5 mg/L

metallic taste

* mg/L is milligrams of substance per liter of water


TGW has chosen to replace the use of Well #1 with the new well, Well #3. Well #3 has substantially lower levels of Mn concentration than Well #1. In addition, Well #3 is being monitored closely since it began production in August of 2010 and now has become the primary water source for many TGW members. The current trend shows that Manganese levels are dropping. It is hoped that this trend will continue and Well #3 levels will eventually become similar to those of the older well, Well #2. Lab results for Well #2 shows manganese is below the MCL and is actually non-detectable (or below 20 PPB). Unfortunately, Well #2 does not produce enough water to supply all TGW needs alone.

Santa Cruz County Environmental Health Service is monitoring our data and considering if TGW will be allowed a waiver for treatment, should its members agree by a majority vote.