This paper compiles a detailed set of in situ chemical oxidation (ISCO) lessons learned pertaining to design, execution, and safety based on global experiences over the last 20 years. While the benefits of a "correct" application are known (e.g., cost effectiveness, speed, permanence of treatment), history also provides examples of a variety of "incorrect" applications. These provide an opportunity to highlight recurring themes that resulted in failures. ISCO is, and will continue to provide, an important remedial tool for site remediation, particularly as a component of a multifaceted approach for addressing large and complex sites. Future success, however, requires an objective understanding of both the benefits and the limitations of the technology. The ability to learn from the mistakes of the past provides an opportunity to eliminate, or at least minimize, them in the future. Over the last 25 years of ISCO application, process understanding and knowledge have improved and evolved. This paper combines a thorough discussion of lessons learned through decades of ISCO implementation throughout all aspects of ISCO projects with an analysis of changes to the ISCO remediation market. By discussing the interplay of these two themes and providing recommendations from collective lessons learned, we hope to improve the future of safe, cost-effective, and successful applications of ISCO.

Zur Bestimmung yon Thiosulfat bei Gegenwart yon Sulfit ver6ffentlichte G u t m a n n 1) in den letzten Jahren eine titrimetrische Methode. G u t I n a n n grtindete sein Verfahren auf jene Beobachtungen yon v. P e c h m ann und M a n c k 2), nach denen sich Thiosulfat, in wSsseriger LSsung mit Cyankalium gekocht, nach der Oleichung:~% S 2 03 ~-KC~ = N% 803 -~-K S CN quantitativ zersetzt. Aus der Menge des gebildeten Sulfocyanats berechnet er das Thiosulfat. Whhrend beim Verfahren G u t m a n n ' s die Flilssigkeit kein Chlorid enthalten darf, abt bei meinen Methoden die Anwesenheit des Chlorids keine stSrende Wirkung aus; zum Beispiel babe ich in 20 c c m 2 °/o Kochsalz enthaltender "/loo-Natriumthiosulfat-15sung 0,01268g Schwefel gefunden, w~hrend der berechnete Wert 0,01282 g betr~gt.Bericht fiber die rortschritte der analytischen Chemie. I. Allgemeine analytische Methoden, analytische 0perationen, Apparate und Reagenzien.