Greetings!

The GREEN BOOK is reopened for public comment!

The Georgia Soil and Water Conservation Commission State Board voted unanimously on Friday, February 21, 2014, to reopen The Manual for Erosion and Sediment Control in Georgia, 6th Edition and testing procedures for public comment and to make changes from comment(s) as needed.

CLICK HERE for information, or questions email certification@gaswcc.org

So I put a little sediment in the creek, no big deal (or is it)? 

How much oxygen does a fish need to survive anyway?  

While there are other factors that can change the chemical composition of water that kill fish (like wet concrete washed into a stormdrain that changes a streams pH to a point of burning fish gills) the reduction of available oxygen for a fish to breath in water caused from pollution is very often the reason fish die. The air we humans inhale is about 21% oxygen or 210,000 parts per million (ppm), while the oxygen our lungs actually absorb is about 50,000 ppm.  Isn't it amazing to know that most fish only need a little more than 5 ppm to live, and a little more than that to successfully reproduce.

The oxygen that fish breathe is not the oxygen that makes up water in the form of H2O. Instead, fish breath O2 (oxygen gas) that is dissolved in the water (DO), from their gills. Many different gases dissolve in liquids, and we see an example of that all the time in

carbonated beverages. In these beverages, carbon dioxide gas dissolved in water rushes out in the form of bubbles when it's not under pressure. Cold water contains more pressure than warm water, which keeps gasses like carbon dioxide and oxygen dissolved.  In other words, a cola is tasty when it's cold and fizzy, but the warmer it gets the more carbon dioxide gas is released into the atmosphere until it finally becomes warm and "flat" with no fizz.  This is what happens to dissolved oxygen in water in a stream, lake, or coastal area, but of course it's a lot more serious when a fish is relying on it for survival.  

In the fish world, oxygen is a rare and precious resource that humans commonly impact through stormwater runoff from urban runoff through storm drains, construction, farming, and timber harvesting.  Pollution added from illicit chemical discharges and malfunctioning wastewater treatment systems also have a huge impact on the amount of dissolved oxygen in a watershed. Most fish and their food source (macro-invertebrates) begin to die when dissolved oxygen levels fall below 2 ppm to 3 ppm.

Suspended sediment is known to increase water temperature which in turn releases dissolved oxygen. Sediment particle adds more surface area to a pond or lake which gives pollutants and algae an extra place accumulate and grow, which significantly decreases dissolved oxygen levels. Other pollutants, like fertlizers and pesticides, grass clippings, animal and human poop, etc. are called nutrients in the stormwater world and they cause bacteria growth in a waterway, which in turns creates an over abundance of the algae and bacteria which then die and decay in the water which removes the dissolved oxygen in the water that fish and other critters must have for survival.  Sediment also adds more problems for us humans when it settles and fills up our drinking water reservoirs and road culverts.  Much of the time, this settling buries fish eggs as well as macroinvertebrates causing a waterway to be impaired which if left unchecked has proven to impair our quality of life.

 The increased likelyhood of more and more pollutants being added to our tributaries is evident when we look at Atlanta's massively growing population.  Because fish are so dependent on dissolved oxygen, it is important that all individuals protect our waters from the pollutants that decrease the amount of available oxygen that fish need to live in and reproduce. 

The work that municipal seperate storm sewer system (MS4) Compliance and Enforcement Inspectors are doing to inspect, water sample, repair and enforce clean water regulations in their local watersheds is critaclly important if we are to be ahead of our future water pollution challenges!