Preplaced aggregate concrete (PAC) is not a new concept.  In fact it is a method of concrete placement that has been around since the late 1930’s.  However, it is often overlooked as an option to repair dams and bridge piers.  In fact, it is one of the most effective forms of underwater concrete repair. 

It is inevitable.  Over time a river will dig out the land over which it flows.  That’s why we have valleys, coulees, and scour problems on every structure we place in its path.  As James Eads would mostly likely attest, rivers cannot be fully tamed and scour repair will always be a constant struggle for anything set in their way.  Bridge piers are one of the most vulnerable structures to scour problems.

1.  Identify and anticipate potential hazardous conditions relevant to the site

• Adverse Weather – Is there likelihood for tornadoes, temperatures extremes, strong winds, flooding, snow storms?
• Air quality or Visibility issues – will this play a factor and increase the danger of the tasks being performed?
• Potentially hazardous tasks being performed – Is the work being performed in a dangerous environment or one that has various exposures?
• Size of the crew and worksite – Is the site large and spread out and are there enough people around to know if someone is missing or needs emergency care?
• Methods of communication – if emergency assistance is needed, how will you contact responders or other crew members?  Are 2-way radios available or do cell phones have service?
• Response time – In remote locations, the time it takes for responders to arrive might be lengthy.  Are you able to respond to an emergency until responders arrive?
• Difficult access to worksite – Accessibility for emergency responders may be an issue.  Are you familiar with the area and can direct responders to your location if needed and no address is available?

2.  Analyze each situation that might lead to an emergency

• What emergency supplies may be needed in this scenario?
• What is the likelihood and severity of the potential incidents?
• Do they have a safe storm shelter or a place to hide from the elements?
• What are the surrounding conditions? Does the worksite present additional chemical or biological hazards?
• What type of emergency evacuation equipment should be available?
• How should we respond and where do we go in case of a fire?
• Talk to the crews and get input about what concerns they may have.

3.  Prepare the site and workers with the appropriate training and supplies 

• Have crews trained in CPR/AED and First Aid
• Locate an emergency shelter or safe location close to the work area
• Make the necessary equipment readily available - Fire extinguishers, spill kits, first aid kits, trauma kits, backboards, stokes basket, emergency rescue equipment.
• Identify phone numbers of local emergency responders, the closest hospital and an emergency plan if something occurs. 
• Lastly, prepare crews for emergency situations and provide them with the appropriate tools to respond to various situations.

Due to their importance, the condition of water-based structures should never be taken for granted, nor should the methods in which they are inspected.  Periodic underwater inspections are crucial to keeping your structure safe and dependable.  Make certain that the dive teams you work with have the experience and know-how to provide you with all the information you need to ascertain current conditions of your structures by keeping three simple things in mind: