period of covered noncompliance
(3) (A) The assessed penalty required under this section shall be paid in quarterly installments for the period of covered noncompliance. All quarterly payments (determined without regard to any adjustment or any subtraction under paragraph (2)(B)) after the first payment shall be equal. (B) The first payment shall be due on the date six months after the date of issuance of the notice of noncompliance under subsection (b)(3) with respect to any source or on January 1, 1980 , whichever is later. Such first payment shall be in the amount of the quarterly installment for the upcoming quarter, plus the amount owed for any preceding period within the period of covered noncompliance for such source. (C) For the purpose of this section, the term “period of covered noncompliance” means the period which begins— (i) two years after August 7, 1977 , in the case of a source for which notice of noncompliance under subsection (b)(3) is issued on or before the date two years after August 7, 1977 , or (ii) on the date of issuance of the notice of noncompliance under subsection (b)(3), in the case of a source for which such notice is issued after July 1, 1979 , and ending on the date on which such source comes into (or for the purpose of establishing the schedule of payments, is estimated to come into) compliance with such requirement.