JOINT FILERS' SIGNATURES

BCP Energy Services Fund GP, LP

By: BCP Energy Services Fund UGP, LLC, its general partner


By:    /s/ Jeffrey Jenkins                             Date: June 20, 2018
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Name:  Jeffrey Jenkins
Title: Authorized Person


Charah Holdings GP LLC


By:    /s/ Mark Spender                                Date: June 20, 2018
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Name:  Mark Spender
Title: Authorized Person


James Bernhard


By:    /s/ James Bernhard                              Date: June 20, 2018
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Name:  James Bernhard
Title: Authorized Person


Jeffrey Jenkins


By:    /s/ Jeffrey Jenkins                             Date: June 20, 2018
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Name:  Jeffrey Jenkins
Title: Authorized Person