B. Description of the Subproject1. Infrastructure Improvement5. The subproject will comprise the rehabilitation of the main, primary and secondary canal network of the existing scheme within Loc Binh District, LangSonProvince. No improvements are proposed for the headworks. The scheme was completed in 1978, though the headworks were built between 1965 and 1968 and remain operational. The scheme was designed to cover a command area of 1,100 ha, over three communes, via a canal system of 40 km in length. The canal system has deteriorated, water losses are severe and as a consequence, the network serves an area of approximately 400 ha. It is also proposed to rehabilitate a 4 km access road to the headworks site from the existing road head at the town of Na Duong, both to improve access to the headworks for maintenance and to improve links to the commune administrative centre at San Vien commune.6. Works to the irrigation system will cover: (i) rehabilitation of the existing concrete lined portion of the canal network, (ii) lining of the existing earthen portion of the canal network, (iii) repair and/or replacement of approximately 500 structures on the canal such as siphons, culverts, valve gates and aqueducts.7. A site inspection confirmed that the dam is firm, and the main outlet valve operational. At the outlet, the majority of the water flows into a concrete channel which is covered with concrete slabs, strong enough to for vehicle movements, for the first few hundred meters. Some water is channeled to a smaller branch, leading to the southeast via a small aqueduct. The covered main canal flows past private dwellings and then continues via open channel and, in places, lengths of aqueduct. The lining of the main canal appears to be grouted stone pitching, or slabs of concrete approximately 50-70 mms thick. While some slabs have been dislodged and some grouting has worn away, most of the lining remains intact. These defects in the lining appeared to be unaddressed by any maintenance activities. The aqueducts also on the main canal remain in service, while some on the secondary canals are leaking and in need of repair.8. Users in San Vien commune, close to the headworks, report generally satisfactory yields from irrigated agriculture though suffering from periods of drought. Further down the network, in Khuat Xa commune, users are able to obtain satisfactory needs but only if they pump water along the network. Yet further, in Tu Doan commune, the users again have to pump water, sometimes from sources other than the irrigation network. Users confirmed that up until approximately 15 years ago, much more water was available and attribute the decline to leakage in the existing system.9. The Irrigation Management Company (IMC) (a government owned company responsible for the O&M of the system) engages staff at each commune to regularly inspect the canals, undertake minor maintenance, and co-ordinate routine maintenance by user groups. Users are obliged to provide seven days of labor to clean the canals each year. The company has a budget for periodical maintenance and repairs, which it considers inadequate. Consistent with this view, numerous repair tasks on the scheme remain outstanding.
đang được dịch, vui lòng đợi..
