July 26 (Reuters) - Denison Mines Corp DML.TO
* Denison reports extension of Cornerstone contract for environmental services business
* Denison Mines Corp - agreement is in relation to management and operation of several of BHP's decommissioned mine sites in Ontario and Quebec
* Denison Mines Corp - DES to be responsible for management and operation of 9 mine sites in Ontario and 2 in Quebec from July 1, 2017 to June 30, 2019
* Denison Mines says its environmental services business entered into new 2 year services agreement with Rio Algom, a subsidiary of BHP Billiton (LON:BLT) Limited