The NFPA 70E Standard details multiple levels of Hazard Risk Categories (HRC) [see table 1.1], also called Levels. The greater the risk: the higher the HRC. Arc Rating is the factor that indicates which HRC is necessary, and can be measured in either ATPV or EBT.
The optimal pH range for brook trout appears to be 6.5-8.0,with a tolerance range of 4.0-9.5.Brook trout occur in waters with a wide range of alkalinity and specificconductance, although high alkalinity and high specific conductance usuallyincrease brook trout production (Cooper and Scherer 1967).
Because of this their level of activity changes as the water temperature changes. If the water temperature fluctuates to much, they will decrease their level of activity accordingly to conserve energy. There seems to be a temperature range of about 20 to 25 degrees F in which most trout can maintain the status quo. Most studies have shown that trout will maintain a normal regimen in temperatures ranging from around 40 to 65 degrees give or take a few degrees on the high and/or low sides.