X0306 4 2018-02-21 0 0000073020 NORTHWEST NATURAL GAS CO NWN 0001605072 Imeson Thomas J 220 NW SECOND AVENUE PORTLAND OR 97209 0 1 0 0 VP, Public Affairs Common Stock 2018-02-21 4 A 0 330 0 A 3730.916 D Common Stock 2018-02-21 4 A 0 370 0 A 2640.457 I See Footnote Common Stock 2018-02-21 4 A 0 886 0 A 3526.457 I See Footnote Common Stock 65.778 I See Footnote Shares are issuable as a result of satisfaction of the performance threshold for 2017 under restricted stock unit awards. Organization and Executive Compensation Committee certification of the satisfaction of the performance threshold occurred on the transaction date. Includes 2,302 time-based restricted stock units (RSUs) granted under issuer's Long Term Incentive Plan. The RSUs vest in two equal installments of shares: 1,151 on each March 31, 2018 and 2019. Shares are issuable as a result of satisfaction of the performance threshold for 2017 under restricted stock unit award, and credited to reporting person's account under the issuer's Deferred Compensation Plan for Directors and Executives pursuant to a prior election. Organization and Executive Compensation Committee certification of the satisfaction of the performance threshold occurred on the transaction date. Shares have been credited to the reporting person's account under the issuer's Deferred Compensation Plan for Directors and Executives. Shares are issuable as a result of satisfaction of performance goals for 2015-2017 under a performance share award, and credited to reporting person's account under the issuer's Deferred Compensation Plan for Directors and Executives pursuant to a prior election. Organization and Executive Compensation Committee certification of the award payout level occurred on the transaction date. Shares held in reporting person's account under the issuer's Retirement K Savings Plan as of January 31, 2018. Shawn M. Filippi, Attorney-in-Fact 2018-02-23