X0306 4 2018-03-14 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 2018-03-14 4 P 0 15552 137.2626 A 30209607 I by Casacde Investment, L.L.C. Common Stock 2018-03-14 4 P 0 98216 136.8334 A 30307823 I by Casacde Investment, L.L.C. Common Stock 2018-03-15 4 P 0 301931 136.6253 A 30609754 I by Casacde Investment, L.L.C. Common Stock 2018-03-16 4 P 0 32300 137.9351 A 30642054 I by Casacde Investment, L.L.C. Common Stock 2018-03-16 4 P 0 43500 137.2272 A 30685554 I by Casacde Investment, L.L.C. This transaction was executed in multiple trades at prices ranging from $137.2000 to $137.3200. 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 $136.2000 to $137.1950. 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 $136.1800 to $136.8500. 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 $137.7100 to $138.0800. 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 $136.7100 to $137.7050. 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 2018-03-16 /s/ Cascade Investment, L.L.C. by Alan Heuberger as attorney-in-fact for Michael Larson, Business Manager 2018-03-16