[en] This report first presents the Saclay centre and its environment: research activities, private sector and public research, environment management system, approach to sustainable development. It gives an overview of the legal framework for effluent release authorizations, environmental monitoring, and regulatory studies. The third part presents the different nuclear base installations (INB) of the Saclay centre (INB number 15, 35, 40, 49, 50, 72, 77 and 101). The next parts deal with atmospheric releases (sources of emission, release control, radioactivity measurements, chemical measurements), liquid releases (types and origins, water cycle and release control, radioactivity and chemical measurements), impact of releases (radiological impact of gaseous and liquid releases, chemical impact of releases), the control of the environment (atmosphere, rain waters, soils, grasses, fruits and vegetables, milk, ambient irradiation, surface and underground waters), some other environmental parameters (electric consumption, water cycle, paper and printers, conventional wastes), the control by independent measurements, incidents and corrective actions (declared significant events), the management of emergency situations (crisis organization, exercises performed in 2011), information and communication actions