Seattle City Light 2016 ANNUAL REPORT | Audited Financial Statements 64 THE CITY OF SEATTLE—CITY LIGHT DEPARTMENT NOTES TO FINANCIAL STATEMENTS AS OF AND FOR THE YEARS ENDED DECEMBER 31, 2016 AND 2015 - 64 - and completing remedial action at the site. The City is responsible for 1/3 of the costs, with the Department’s share at 90% and SPU’s share at 10%. The implementation of the RI work plan is ongoing and will continue into the first quarter of 2016. The schedule for the feasibility study (F/S) anticipates a draft F/S document in May 2018 and the Final F/S document in November 2018. Total estimated costs for the current order are $6.0 million. Costs to date are approximately $6.8 million with an additional $383K projected through completion of the F/S. Boeing and the City will each pay 100% of costs for remedial action at their own facilities. The Department has included in its estimated liability those portions of the environmental remediation work that are currently deemed to be reasonably estimable. Cost estimates were developed using the expected cash flow technique in accordance with GASB Statement No. 49. Estimated outlays were based on current cost and no adjustments were made for discounting or inflation. Cost scenarios were developed that defined a particular solution for a given site. Scenarios considered relevant potential requirements and alternatives for remediation of a site. Costs were calculated on a weighted average that was based on the probabilities of each scenario being selected and reflected cost-sharing agreements in effect. In addition, certain estimates were derived from independent engineers and consultants. The estimates were made with the latest information available; as new information becomes available, estimates may vary significantly due to price increases or reductions, technology, or applicable laws or regulations. The Department is aggressively pursuing other third parties that may have contributed to the contamination of superfund sites for appropriate cost sharing. The Department’s estimate for realized recoveries was $3.0 million and $4.1 million at December 31, 2016, and 2015, respectively, primarily representing an interfund receivable from SPU for recovery of remediation costs incurred related to the lower Duwamish Waterway site. The Department’s estimate for not yet realized recoveries from other parties for their share of remediation work performed that partially offset the Department’s estimated environmental liabilities was zero at December 31, 2016, and 2015. As of December 31, 2016, and 2015, environmental costs of $83.1 million and $31.2 million were deferred primarily for cleanup estimates of the Department’s responsibility for the Lower Duwamish Waterway and East Waterway Superfund Sites; and these costs will be recovered through future rates in accordance with GASB Statement No. 62. The changes in the provision for environmental liabilities at December 31, 2016, and 2015 are as follows: ($ in millions) 2016 2015 Beginning environmental liability, net of recoveries 45.9 $ 57.6 $ Payments (10.0) (8.4) Incurred environmental liability 50.8 (3.3) Ending environmental liability, net of recoveries 86.7 $ 45.9 $