With Yuan 's support , he began the project to clear Bian River of silt .
He then wrote a detailed report to Yuan Zai , who had become a powerful chancellor by that point , explaining the benefits of the Bian River route .
With Yuan Zai 's support , he began the project to clear Bian River of silt .
He then wrote a detailed report to Yuan Zai , who had become a powerful chancellor by that point , explaining the benefits of the Bian River route .