The Kowloon Railway Company has conducted an assessment study on eight proposed rail tracks to Lok Mah Chau terminal. The assessment study demonstrated that those proposed rail tracks construction are not feasible because they would raise up the total cost by 13 billion to 33 billion and prolong the completion time beyond 2004. With the consideration of money, time and expected negotiation, the company decided to choose the track which passed through the Long Valley, one of mangroves in Hong Kong.

After considering the environmental assessment study, the Environmental Protection Department eventually refused to grant the Corporation with the permit because the corporation failed to show there are no alteratives to the chosen one.

In the public, it is thought that Long Valley is defined as No Construction area according to the technical memorandum for Environmental Impact Assessment. So the company cannot initiate any track construction in Long Valley.

Yet, according to the assessemen study, the company has demonstrated that according to Outline Zoning Plan, Long Valley has never ever been zoned as Area of Important Natural Education. Instead it is only defined as agricultural land which does not exclude any construction on the site.

Apart form planning issues, the study also hightlighted other social and technical difficulties if other proposed alteratives such as North line, South Line 1, South Line 2, Fan Ling, Fan Ling highway, Lo wu line and "Double Fish stream" line would have been accepted. Technically, other proposed lines may involve demolishing the existing abbatoir, sewerage treatment plant or Sheung Shui Railway station, rebuilding new tracks, maintaining the existing streams and realigning Tung Kong channel. Socially they may encounter land resumption and compensation, and security issue.

Subsequently the company chose the track which passes through the Long Valley straightly.