X0306 4 2018-03-12 0 0000031462 ECOLAB INC. ECL 0000902012 GATES WILLIAM H III ONE MICROSOFT WAY REDMOND WA 98052 0 0 1 0 0001052192 CASCADE INVESTMENT, L.L.C. 2365 CARILLON POINT KIRKLAND WA 98033 0 0 1 0 Common Stock 2018-03-12 4 P 0 20540 136.9232 A 29845595 I by Casacde Investment, L.L.C. Common Stock 2018-03-12 4 P 0 79460 135.8657 A 29925055 I by Casacde Investment, L.L.C. Common Stock 2018-03-13 4 P 0 23788 137.2432 A 29948843 I by Casacde Investment, L.L.C. Common Stock 2018-03-13 4 P 0 245212 136.6484 A 30194055 I by Casacde Investment, L.L.C. This transaction was executed in multiple trades at prices ranging from $136.6000 to $137.2100. The price set forth above reflects the weighted-average price per share. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transactions were effected. This transaction was executed in multiple trades at prices ranging from $135.5850 to $136.5700. The price set forth above reflects the weighted-average price per share. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transactions were effected. This transaction was executed in multiple trades at prices ranging from $137.1700 to $137.2650. The price set forth above reflects the weighted-average price per share. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transactions were effected. This transaction was executed in multiple trades at prices ranging from $136.1700 to $137.1600. The price set forth above reflects the weighted-average price per share. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transactions were effected. /s/ Alan Heuberger, Attorney-in-fact for William H. Gates III 2018-03-14 /s/ Cascade Investment, L.L.C. by Alan Heuberger as attorney-in-fact for Michael Larson, Business Manager 2018-03-14