Changes

First a trench needs to be dug. Its position is marked out using pegs. Then it is excavated and the soil placed downstream. It can also be dug out into bedrock. It should then be checked for weathering zones and cracks. Round bars are placed vertically along the trench to reinforce it. Then a foundation is laid consisting of 2 layers of cement with barbed wire in between. Once this has set, the trench is filled with masonry or mortar and hardcore. The wing walls and final dam wall can then be constructed. Finally any exposed parts of the construction are plastered. 首先，需要挖取一个沟渠，用桩子标记地点。随后，挖取沟渠，将土壤置于下游。也可以挖到基岩处。然后，需要检查风化带和裂缝。圆形杆子沿沟渠垂直放置，用以加固。之后，铺设地基。地基由两层含带刺铁丝网的水泥构成。一旦地基铺设完成，沟渠由砖石或灰浆和岩石碎块填满。随后，可建造翼墙和最终的坝墙。最后，粉刷建筑物上任何裸露的部分。

====Building the sand dam (and wing wall)建造沙坝（以及翼墙）===='''General advice on cement对于水泥的总体建议''': A ：A common cause of cracks in structures and linings (e.g. in tanks, dams, waterways, wells) is errors in mixing and applying the cement. First of all, it is important that only pure ingredients are used: clean water, clean sand, clean rocks. The materials have to be mixed very thoroughly. Secondly, the amount of water during mixing needs to minimal: the concrete or cement needs to be just workable, on the dry side even, and not fluid. Thirdly, it is essential that during curing the cement or concrete is kept moist at all times, for at least a week. Structures should be covered with plastic, large leaves or other materials during the curing period, and kept wet regularly.