Dear Manager,
I'm a middle school student in TianJin,named LiMing.Here I write to you to give some advice for your company.
My hometown is a beautiful place,where there is a river nearby.The water in the river used to be very clear.But since your company was built later on and it poured waste water to our clear river,our river was poured ,and it has made serious problems.
So I hope that you can take measures to solve the problems and keep our river clear as before.
Sincerely,
LiMing
有些句子你可以试着改一下,大致就是这样的思路了,先说你的来历,然后说明污染的内容,最后希望厂长采取措施.