求翻译：付款方式分期支付，原则上签订合同预付合同额的1/3，通过评审预付合同额的1/3，环评审批后付合同额的1/3是什么意思？

Method of payment instalments, signed a contract in principle one-third of the contract amount paid in advance, by review pre-one-third of the contract amount, one-third of the EIA approval to pay the contract amount