According to the ENVIRONMENTAL PROTECTION LAW (EPL), the supplementary facilities for pollution and other public nuisances to all the construction projects must be simultaneous with the main projects in their design, construction and operation. This is called "Three simultaneities" system (TSS).
   
"Three simultaneities" system is an essential measure and an important environmental protection stipulation in an effort to strictly control new pollution and prevent new environmental pollution and deterioration. It is complimentary with the EIA system and an effective tool to avoid new environmental pollution and deterioration. It is the concretization, institutionalization and standardization of the ruling principle of "priority to prevention" of EPL. It serves as an important step in strengthening the environmental management for the construction projects and also as an effective economic and legal method against the continual deterioration of the environment quality.
  
TSS is the regulatory system published the earliest in the field of environmental management. This original creation of China, showing its Chinese characteristics has been proved effective in practice.

Policies on the supervision of TSS

To ensure a good implementation of TSS, in March 1986 the Environment Committee of the State Council and the State Planning & Development Commission jointly issued the document (Serial Number: State Environment No.86003) with the title ENVIRONMENTAL PROTECTION SUPERVISION REGULATIONS ON CONSTRUCTION PROJECTS. Together with the March 1987 ENVIRONMENTAL PROTECTION DESIGN STIPULATIONS ON CONSTRUCTION PROJECTS, they stipulate the detailed measures in carrying out the TSS as follows:

An examination and approval system is introduced and EI reports are required for all the construction projects that causeimpact on environment. The corollary supplementary facilities  against pollution and other public nuisances to all the construction projects must be simultaneous with the main projects in their design, construction, and production, referred to as the TSS.

Units undertaking projects are responsible for the EI report forms, addressing the environmental impacts and mitigation measures stipulated for the preliminary design and the normal operation of the anti-pollution facilities.
  
Units undertaking projects and their senior authorities are responsible for environmental mitigation. Environmental mitigation should be reflected in all the links of site identification, project design, and arrangement in the construction process and completion acceptance. Investment, equipment and materials, etc. that concern environment mitigation should be arranged and undertaken at the same time with the main projects. Environment mitigation facilities must be simultaneous with the main projects in their design, construction, and operation. Those who do not comply with these requirements will be denied to go to the acceptance process and be forbidden to go into operation. Any non-compliance will result in responsibility investigation.

EIA reports should be based on the feasibility study of the capital construction projects.

In the design phase of a capital construction project, post-evaluation – of environment impacts is required. A feasibility study report should address issues as regards the surrounding environmental conditions, major pollution sources and pollutants, ecological changes that may be brought about by resource exploitation, pollution mitigation, investment to environmental mitigation to meet environmental standards and etc. Preliminary design should contain chapters on environmental impact mitigation that deal with basis on which mitigation measures are  designed, and issues such as major pollution source, main pollutants and their means of discharge, environmental standards proposed to be employed, environment mitigation facilities and their basic process flow, preventive measures to ecological changes, and investment estimate on environment mitigation, etc. are addressed. The design of working drawings must be in strict accordance with the environment mitigation chapters and the approved preliminary design documents.

In the construction phase, environmental mitigation facilities must be constructed at the same time with the main project. During the construction process, the surrounding environment should be protected to reduce or eliminate any unnecessary negative impact. Dust, noise, vibration and other pollutants and factors should be prevented or mitigated. Environment Protection authorities can conduct on-the-spot inspection and the units undertaking construction must present the materials on request.

Before the formal production or operation of a construction project, the unit undertaking construction must submit a Completion Acceptance Report of the Environmental Mitigation Facilities showing the operational conditions of the facilities, treatment effects and standards that are met. Formal production or operation can commence only after all the requirements by the environment protection authorities are met and the issuance of the Acceptance Certificate of Environment Mitigation Facilities.
 
The December 1989 Environment Protection Law summarized the lessons and experience drawn from TSS. Article 26 defines that Pollution mitigation facilities of the construction projects must be simultaneous with the main projects in their design, construction, and operation. In view of the low operation rate and the lack of beneficial performance of such existing facilities, this article also adds that without authorization, such facilities should not be removed or unused. Those who do have such necessity must apply the approval by the local administration authorities in environmental protection. Article 36 deals with the stipulation on violation against TSS.