Loading Analysis

Comments By Alice Tulloch, Tulloch Engineering

1. Whenever you have mentioned an important geographic location, make sure it's shown on one of your maps, ex. Maze Blvd.

2. The exec. summary and Recommendations for Future Work would benefit from a brief discussion of what this report does not yet cover in the overall TMDL development, setting the big picture for readers. I am specificially thinking of the fundamental framework of a TMDL. "The TMDL specifies the amount of a particular pollutant that may be present in a water body, allocates allowable pollutant loads among sources, and provides a basis for attaining or maintaining water quality standards." (EPA Draft TMDL regs, 8/23/99) The Strawman focuses on the first step. However, a major element still to be addressed is the allocation among sources. The generic formula for TMDL is background sources + a safety factor + man-made sources shall not exceed the load at which an impairment is triggered. The whole TMDL process is still in need of more information to distinguish between background and man-made sources from each tributary. Further studies are needed. This is a large gap in our understanding of how we might actually address the DO deficiency. This gap will be important to stakeholders. We have not developed data or run model simulations to quantify these two categories. It is conceivable that, due to the Port and the export flows, that eliminating all man-made sources would not correct the DO deficiencies. Point and non-point dischargers are going to want to know the magnitude of these relationships. The possible scenario that the current assimilative capacity is inadequate to accept all the background sources leads me to think about the practicality provisions of the Porter-Cologne Act. When setting regulations, the SWRCB must consider whether reduced pollutant levels are attainable, measurable, and economic. The second TMDL step is all about allocating responsibility and the bill, among stakeholders, even if Russ's aeration at the DWSC is the magic fix.

3. The report could also take the opportunity to discuss the difference between DO and other pollutants. Low DO is an impairment, but not itself a pollutant. Your discussion does a good job of bringing out the three main factors that create the impairment, flow, morphology and loading.

4. Help the reader a bit more with the basic science of BOD. We are using 10 day BOD at Mossdale as an measure of the load that will effect the DWSC.

Please include a brief discussion on why 10 day BOD is okay, compared to the 3 day travel time from Mud & Salt Slough. Under what circumstances would this simplification not hold true? How sensitive is the DO modeling to the assumptions in the decision to use 10 day?