X0306 4 2018-03-01 0 0000073020 NORTHWEST NATURAL GAS CO NWN 0001661934 Burkhartsmeyer Frank 220 NW SECOND AVENUE PORTLAND OR 97209 0 1 0 0 SVP & Chief Financial Officer Common Stock 2018-03-01 4 F 0 651 52.15 D 5740 D Shares were withheld by the issuer to cover withholding taxes on issuance of shares due to vesting of 375 restricted stock units (RSUs) with performance threshold, and vesting of 1,504 time-based RSUs. Organization and Executive Compensation Committee certification of satisfaction of the performance threshold and vesting for 375 RSUs was reported on Form 4 filed on February 23, 2018. The 1,504 time-based RSUs are part of 6,016 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 May 23, 2017. Includes 4,512 time-based restricted stock units (RSUs) granted under issuer's Long Term Incentive Plan. The RSUs vest in three equal installments: 1,504 shares on each March 1, 2019, 2020 and 2021. Shawn M. Filippi, Attorney-in-Fact 2018-03-05