# Presentation: 433628

## slide 1

**slide 1**

**Notes:**
circular.2BRIEFING.04.21.06.ppt

## Water-supply system

***Treatment***

**slide 2**

**Ambient **
**ground **
**water**

**Drinking **
**water**

## No VOC Detection

**Hawaii**

**Oahu**

**Alaska**

**No VOC Detection**

**VOC Detection**

**Notes:**
Findings: VOCs were detected in aquifers throughout the Nation.

Conclusions: Many of the Nation’s aquifers are vulnerable to VOC contamination.

## VOC concentrations in aquifers

**Not **
**detected**

**       ****Detected, **
**below 1 ppb**

**slide 4**

**    ****Detected, **
**above 1 ppb**

**Notes:**
Finding: Most aquifer samples had no VOCs detected or the concentration was below 1 part-per-billion (ppb)

Conclusion: Few aquifer samples have VOC concentrations that may affect the potability of ground water for drinking water

## Chloroform was the most frequently detected VOC in aquifer samples

**slide 5**

**DETECTION FREQUENCY, IN PERCENT**

**Toluene**

**TCE**

**PCE**

**Chloroform**

**MTBE**

**Notes:**
Assessment level of 0.2 micrograms per liter

Conclusion: Recycled water with a history of chlorination is an important source of chloroform (and other THMs) for aquifers.

## TCE

**slide 6**

**DETECTION FREQUENCY, IN PERCENT**

**Toluene**

**TCE**

**PCE**

**Chloroform**

**MTBE**

## MTBE

**slide 7**

**DETECTION FREQUENCY, IN PERCENT**

**Toluene**

**TCE**

**PCE**

**Chloroform**

**MTBE**

## Domestic wells

**Domestic wells**

**slide 8**

**Public wells**

**and**

## Hawaii

**Hawaii**

**Oahu**

**Alaska**

## Public

**Public**
** ****wells**

**Domestic**
**       ****wells**

**DETECTION FREQUENCY, IN PERCENT**

**concentrations below MCLs and HBSLs**

**concentrations greater than MCLs**

**slide 10**

## VOCs with concentrations greater than MCLs

**slide 11**

**DBCP****	****	****	****	****X**
**1,2-Dichloropropane****	****X****	****	**
**EDB****	****	****	****	****X****	****	****	****	**

**1,1-Dichloroethene****	****X****	****	****X****	****    ****	****	**
**Vinyl chloride****	****	****	****	****X**

**TCE****	****	****	****	****X****	****	****X**
**PCE****	****	****	****	****X****	****	****X**
**Methylene chloride****	****	****	****X**

**Domestic**

**Compound**

**Public**

**Well type**

**Fumigants**

**                            ****Chemical**
**production**

**Solvents**

**Group**

**Notes:**
VOCs found at concentration(s) of potential human-health concern (compounds listed by decreasing number of concentrations of potential concern).

Finding: Only 8 compounds had concentrations of potential human-health concern.

Conclusion: Most VOC concentrations are not anticipated to cause adverse human-health effects.

## THMs in domestic and public wells

**Chloroform**

**Bromodichloromethane**

**Dibromochloromethane**

**Bromoform**

**DETECTION FREQUENCY, IN PERCENT**

**slide 12**

**Domestic**

**Public**

**Notes:**
Assessment level of 0.2 micrograms per liter.

Finding: Chloroform and other trihalomethanes (THMs) were more frequently detected in public wells.
Conclusion: Anthropogenic sources of the THMs in public wells should be examined further.

## Summary 

**Widespread occurrence of VOCs**
**Concentrations seldom of **
**      ****potential concern**
**Large number of vulnerable ****	****aquifers**

**slide 13**