Unfortunately, writing your senator is not going to do shit. Logging companies stand to make millions off of each of these timber sales, and a shabbily organized letter writing campaign at the request of a inneffective reformist environmental group is going to have a minimal (if that) effect. The only way to prevent the logging of more old growth in the biscuit is to physically prevent it from happening and by directly targeting the companies responsible in a way that will make them beg for forgiveness.
More people need to be in the Biscuit right now, defending in a way that will actually physically stop logging from taking place; not in some symbolic protest from your supposed moral highground of your lawn chairs. More people need to be on the roads, in the trees, on the bridges, and on the forest floor, defending the forest in the most literal sense. More people need to be on the doorsteps of the CEOs of the companies responsible, night and day, making their life hell; making them wish they had never heard of the Biscuit.
More importantly than stopping logging in the Biscuit, people need to be fighting to stop the logging industry. The only real way to do this is not by running from timber sale to timber sale, stopping what can be stopped, but by running these corporations into the ground. "It is time to stop adhering to inneffective tactical dogmatism," a wise friend once told me, "It is time to use tactics that work."