InsideClimate: Federal agencies have so far not decided whether to undertake an assessment of the ecological harm caused by ExxonMobil's pipeline break, which spewed a tarry oil slick into yards, streets and creeks in a central Arkansas town. For now, they're leaving it to state agencies to decide whether and how to quantify and counteract the environmental damage. The rupture in the Pegasus pipeline on March 29 dumped up to an estimated 294,000 gallons of Canadian heavy crude in Mayflower, Ark.including in...