Cov ntawv hlau phaj yog ib hom hlau nrog lub xauv, thiab nws cov ntu ntu yog ncaj, zawj thiab Z-puab, thiab muaj ntau qhov ntau thiab tsawg.
thiab cov ntaub ntawv sib cuam tshuam.Feem ntau yog Larson, Lackawanna thiab lwm yam.
Nws qhov zoo yog: siab zog, yooj yim rau kev tsav mus rau hauv cov av tawv txheej;tuaj yeem tsim hauv dej tob, yog tias tsim nyog, ntxiv kev txhawb nqa inclined los ua lub tawb.Kev ua tau zoo dej tsis zoo;tuaj yeem tsim cofferdams ntawm ntau cov duab raws li qhov xav tau, thiab tuaj yeem rov qab siv tau ntau zaus, yog li nws tau siv dav.