On November 23, 2011 the NTSB provided a response to a letter submitted by AGA
to request a clarification regarding the intended scope and applicability of recommendations P-10-1 through P-10-4. NTSB stated that AGA's interpretations of NTSB's intent were correct. NTSB confirmed that these safety recommendations were not intended to be codified into state and Federal rules and regulations. Further, the NTSB clarified that the postconstruction hydrostatic test recommendation encourages PHMSA to remove the grandfather clause and to require all pre-1970 gas transmission pipelines to undergo a hydrostatic pressure test that incorporates a spike test.