3 Permit requirements

3.1 Monitoring time frame

From 401 water quality certification conditions:

“The UPRR will conduct the required monitoring until the results demonstrate that the Salinity Performance Standard Ranges are being met and trends indicate they will continue to be met into the future. The UPRR may request cessation of monitoring and adaptive management by submitting a Completion Report that includes no less than 5 years of monitoring results after the most recent causeway modification affecting water and salt transfer. If after 60 days of public notice the Director concurs that the Salinity Performance Standard Ranges are met, the Director will approve cessation of monitoring and adaptive management.”

3.2 Breach geometry

Causeway geometry is evaluated twice per year for the first three years following the causeway breach, then annually. There are four geometry performance measures:

  1. Channel bottom width, measured under the bridge at the rail centerline
  2. Cross section area based on water surface elevation (WSE) of 4200 ft
  3. Average water depth at bridge based on WSE of 4200 ft
  4. Invert control berm width

3.3 Gilbert Bay salinity

Gilbert Bay salinity is evaluated four times per year. Monitoring is conducted at 3 locations in Gilbert Bay and 1 in Gunnison Bay. Under the CMMP, average Gilbert Bay salinity values are calculated through the application of an empircal USGS model formula to bathymetrically averaged density measurements. Minimum and maximum ranges were derived via a USGS/UPRR causeway and salinity model.

Figure 3.1: Causeway salinity performance range.