Case Study - Broken Water Main

LEWAS Lab Civil Engineering Team

On June 26th, 2012 at 4:30 pm a water main broke in the town of Blacksburg, VA at a location within the LEWAS watershed. Students monitoring the stream noticed that the water was very turbid and immediately deployed the water quality Sonde. The water main continued to spill water until 9:00pm when it was contained.

Figure 1. Water Main Break Location

Overall approximately 760 m3 of treated water was spilled. From this event the LEWAS lab noticed that there was a significant impact on the water quality of Webb Branch. Water quality changes included:

  • Turbidity increased significantly
  • pH decreased
  • Conductivity decreased
  • Significant fish kill
  • Strong fishy odor from water

The images below illustrate the before and after conditions of the water main break. The image to the left shows the baseflow conditions of the site on June 13th, 2012 before the spill. As you can see the water is relatively clear and you can see the rocks and biofilm on the bottom of the stream. The two images to the right show the stream during the water main break on June 26th, 2012. The water in these pictures is extremely turbid and there is no visibility through the water.

Figure 2. Varying Turbidity in Webb Branch

Data from the event shows that there was a 100-fold increase in turbidity during the water main break. The Sonde was deployed at 7:45 PM and the turbidity in the water was over 300 NTU, significantly higher than the 1-1.5 NTU during June 13th, 2012. The turbidity finally recovered back to previous levels a day later as can be seen on the June 27th, 2013 plot.

Figure 3. Turbidity Variations

The event had a significant impact on the aquatic ecosystem. There was a large fish kill due to the water main break. The team noticed over 100 dead Blacknose Dase (Rhinichtys atratulus) and 20-30 dead White Sucker (Catstomus commersonii) fish. The likely cause of death was from chlorination of the treated water or the increase in turbidity.

Figure 4. Dead fish in Webb Branch