AN ambitious plan to clean up the New Territories, where serious abuse of farmland is rampant, will cost taxpayers about $1.9 billion in its initial stages. Governor Chris Patten directed in his policy speech last October that the countryside be preserved, and the Planning, Environment and Lands Branch has now drawn up a detailed plan. While a key objective is to improve and protect the environment, Mr Patten's plan will also generate more residential land to meet Hong Kong's pressing housing demands. More than 200 officers will be deployed on the five-year task, 162 of them forming a special taskforce under the Lands Department to attack the blackspots where there has been blatant ''unauthorised development''. The other 40 staff outside the taskforce will form two special teams under the Planning Department to prevent abuse recurring at sites which have been cleared. Officials' preliminary assessments indicate that urgent action is required in the northwest New Territories, on about 300 hectares of land in Sek Kong, San Tin, Ngau Tam Mei, Tai Sang Wai, Tuen Mun-Yuen Long Corridor, Ha Tsuen and Lau Fau Shan. Sek Kong is understood to be the area to be tackled first. The programme will involve vigorous enforcement action against ''unauthorised'' land use, administrative measures to clean up the blackspots through relocation or termination of operations and site improvement and reinstatement works. Noting the importance of community support in the Government's cleaning up programme, the Government also intends to set up a special committee to monitor the work of the taskforce and to reflect community views on how undesirable land uses in the New Territories should be tackled in the short and long term. The committee will be chaired by an independent expert with 12 to 15 members and representatives from government departments dealing with land and New Territories issues. Secretary for Planning, Environment and Lands, Tony Eason, has estimated that about 700 hectares of agricultural land in the New Territories had been converted to open storage. Uses include: Storage of new left-hand drive vehicles and new or second-hand construction machinery; Car stripping, car repairing and car assembly yards; Storage of container boxes and parking of container vehicles. Of the total, 550 hectares were converted into open storage before the enactment of 1991 Town Planning Ordinance, which aimed to contain the problem, while the remainder were converted after 1991 and classified as ''authorised developments''. Officials maintain that the haphazard conversion of agricultural land in the New Territories into open storage and dumping sites has led to widespread degradation of the countryside, causing flooding, health hazards and major environmental problems. The taskforce is expected to: Clear operations illegally established on government land, followed by appropriate reinstatement works such as landscaping. Step up enforcement and prosecution action on ''unauthorised developments'' under the Town Planning Ordinance. Enforce lease conditions on operations with illegal structures on sites. Terminate through negotiations sites supporting operations which can no longer be tolerated. Relocate operations which serve an important economic function to more suitable sites, controlling their operations. In 1994/95 alone, the Government estimates that the programme will require $21.5 million in ongoing spending such as staff costs and $22.5 million in one-off expenditure. The latter includes ex-gratia payments, site formation and improvement works, including landscaping and preventive measures against further illegal occupation and dumping. To facilitate prompt action, it is also proposed that the Director of Lands be authorised to approve projects or spending commitments of up to $5 million without having to seek Legislative Council Finance Committee approval.