X0306 4 2018-03-01 0 0000073020 NORTHWEST NATURAL GAS CO NWN 0001686243 Palfreyman Justin 220 NW SECOND AVENUE PORTLAND OR 97209 0 1 0 0 VP Strategy & Bus. Dev. Common Stock 2018-03-01 4 F 0 271 52.15 D 2552 D Shares were withheld by the issuer to cover withholding taxes on issuance of shares due to vesting of 243 restricted stock units (RSUs) with performance threshold, and vesting of 516 time-based RSUs. Organization and Executive Compensation Committee certification of satisfaction of the performance threshold and vesting for 243 RSUs was reported on Form 4 filed on February 23, 2018. The 516 time-based RSUs are part of 2,580 time-based RSUs that have been reported as shares beneficially owned by the reporting person since initially reported on the reporting person's Form 3 on October 5, 2016. Includes 2,064 time-based restricted stock units (RSUs) granted under issuer's Long Term Incentive Plan. The RSUs vest in three installments: 516 shares on each March 1, 2019 and 2020, and 1,032 shares on March 1, 2021. Shawn M. Filippi, Attorney-in-Fact 2018-03-05