City of Mission Viejo:

City of Mission Viejo:

FMS was engaged as the project’s EMI Consultant to conduct an AC (60 Hz) electromagnetic field (EMF) assessment of the existing transmission corridor located in Mission Viejo, CA. The corridor contains two (2) 220 kV circuits and three (3) 66 kV circuits, owned by the local utility, Southern California Edison (SCE).

The EMF site survey was authorized to secure a view of magnetic field conditions present at various locations within the corridor and at the edge of the corridor right-of-way (ROW) and to provide a context for those measurements (and measurements taken by others). In the course of the study, FMS:

1. Took spot measurements at 32 locations along the corridor and corridors ROW, generally at locations previously measured by Sage Associates.

2. Placed logging magnetic field meters at 4 sites (similar to the Sage Report), including two edge-of-the-ROW sites. One of the ROW locations approximates a hypothetical measurement location of the SCE computer model which was produced as part of the California Public Utilities Commission siting process. The meters were set to record long-term data at 1-minute intervals.

3. Created (based on actual load data received from SCE) computer simulations of the fields generated by currents in the lines.

4. Selected, from the recorded long-term measurements, one-hour ranges of time during which measured field values were relatively stable.

5. Input line load data from the same, stable time period into the FMS computer simulation, and tested conformance of the model to the long-term measurements.

6. Selected, from all actual loading conditions during the measurement period, the maximum load conditions for each of the lines and created models of:
   1. Maximum Load
   2. 90% Load
   3. 80% Load
   4. 70% Load
   5. 60% Load and
   6. 50% Load

7. Compared the computed values from this report with those of the SCE model, the FMS measurements and the Sage measurements, to test conformance and reasonability.

The data from this study supported the following conclusions:

1. Conditions, within the actual loading data of this study, generated field levels which encompass the measurements recorded in the Sage study.
2. Conditions, within the actual loading data of this study, generated field levels which encompass the calculations of the SCE model, as reported to the CPUC.
3. Both the Sage report and the SCE model, in our view, meet the test of reasonableness.