(a) An ERISA Event occurs with respect to a Pension Plan or Multiemployer Plan which has resulted or could reasonably be expected to result in Liability of any Company under Title IV of ERISA to such Pension Plan, such Multiemployer Plan or the PBGC in an aggregate amount in excess of $5,000,000, or (b) General Partner or any ERISA Affiliate fails to pay when due, after the expiration of any applicable grace period, any installment payment with respect to its withdrawal Liability under Section 4201 of ERISA under a Multiemployer Plan in an aggregate amount in excess of $5,000,000.