An independent forensics team cited thinning concrete and lack of reinforcement as possible causes of a spillway failure in February at California’s massive Oroville Dam.

在美国最高水坝的主要斜道中出现了一个40英尺的洞，这导致了另外两个渠道的问题，并迫使该州的水资源部呼吁撤离近20万人。

On May 10, the agency posted a memo from an independent forensics team that listed possible reasons for the failure. The dam’s overly large slab placement that could have led to the cracking were caused by design flaws when the dam was built 50 years ago, according to the report.

Other issues, such as clogged drains due to tree roots, insufficient slab repairs and an increase in spillway discharge shortly before the slab failure, were linked to maintenance and operations.

该报告还指出，扩展的干旱可能会在已经粘合的基础上缩小土壤。空化被认为不是重要因素。

紧急溢洪道（一个无用的山坡）是在2月的暴风雨中首次在大坝历史上投入使用，并且在几个小时内开始显示侵蚀的迹象。该报告指出，导致波峰控制结构的头饰的松散土壤，溢洪道底部的能量耗散不足以及波峰结构下游的侵蚀防护。

DWR代理总监比尔·克罗伊尔（Bill Croyle）表示，尽管计划要求改善紧急溢洪道，但目标是提高从主要插座的安全流量水平，因此不必再使用替代版本。

The preliminary findings will be “taken into consideration” as the agency develops plans to reconstruct the spillway before November, says Croyle. A final forensics report will not be complete until the fall.

A $275 million recovery contract was awarded to Kiewit in April. The agency faced calls from residents and politicians to release the entire forensics report after it did not release details about the contract due to security concerns.

独立的取证团队包括来自私人和政府部门和学术界的六名专家。