How to interpret contamination plumes

The source of the contamination will have the highest concentration

If the contamination spreads out evenly, this is non-point source contamination and no one specific spot is causing the

contamination

If the contamination levels get lower as they move away from the source then this is know as point source pollution and one

particular spot is causing the pollution.

First you identify the MCL • The number is a concentration expressed in

ppm or ppb.

• It is the maximum amount that a person can be exposed to without negative effects.

Next, look at the key

• What code corresponds to the MCL?• In other words, which code has the MCL in its

range?• Any well that has a code equal to or HIGHER

than this is UNSAFE!

Code that have a range that contain the MCL could be contaminated or not, so we err on the side of caution and consider all wells in the code unsafe.

• Ex if the MCL= 0.5 ppb • Code 2 = 0.11 - 0.8 ppb• 0.5 ppb is in between so some code 2 wells are

unsafe and others are not• If I gave you a glass of code 2 water would you

drink it?• No….assume it is unsafe

color code the wells

a line separating the safe areas from the unsafe areas is called the leading edge

Now… draw a leading edge around all of the unsafe areas

Shade in all of the unsafe areas

Can you see the source?The concentration will be highest at the source (star)

What direction is the plume moving?From higher codes to lower codes (arrow)

This map is called an PLUME iso-map

• Iso means same• Areas that are the same concentration will be

connected and color coded the same color.• The areas that are unsafe and shaded in is

called the plume

• NOW DRAW THE PLUME ON YOUR FRUITVALE MAP. GO TO THE NEXT SLIDE.

Well dataCode Wells with this code

orange 1, 2, 5, 6, 11, 15, 16, 18, 22

yellow 3, 7, 14, 17, 19, 20, 31, 32, 33, 34, 36, 37, 38, 39, 40

green 4, 12, 13, 21, 23, 25, 28, 29, 30, 35

Blue-green X, 9, 10, 26, 27, 24

blue 8

Remember the MCL is 1ppb.

Which codes are safe?

Which are unsafe?

Draw your plume in PENCIL!

Do Not shade in the safe areas.