Optimization of the CMS forward shielding

A first realistic version of the CMS forward shielding was presented in the 1999 Engineering Design Review. It was discovered that the background increased by a factor of 2 with respect to the TDR where an idealized shielding had been assumed. This note describes the optimizations implemented in the realistic shielding with the aim to recover the TDR performance. An optimization of the shielding geometry, the beam pipe and a filling of major cracks has allowed to achieve the goal. Although the differences to the TDR are very minor, these new calculations should be understood as an update to those presented in the TDR.