Before revision:  Under Markovian assumption, we show that the base capacity is in fact deterministic and coincides with the free boundary of the  optimal stopping problem naturally associated to the singular control one. For a Cobb-Douglas production function, if the diffusion's coefficients are constant, we are able to show that the free boundary is a continuous function of the time so to remove Assumption- Cfb in Chiarolla and Haussmann (2009) .
After revision:  Under Markovian assumption, we show that the base capacity is in fact deterministic and coincides with the free boundary of the optimal stopping problem , when the coefficients of the controlled diffusion are deterministic functions of time. This is a novelty in the literature on finite horizon singular stochastic control problems. As a subproduct this result allows us to obtain an integral equation for the free boundary is a continuous function of the time so to remove Assumption- Cfb in Chiarolla and Haussmann (2009) .