Your first option (present continuous) is a grammatically correct sentence, but it is not what would be most often used for an event in a chronology. It might be used if it was used to introduce another simultaneous event, such as:
The soil material is being rejected for dumping. Everyone is getting frustrated.
or if it is an event that is repeated or ongoing:
The soil material is being rejected for dumping, time and time again.
Your second option (noun phrase) is a grammatically correct noun phrase, but it is not a sentence, and not at all how someone would describe this event in a chronology. (Unless it was the title of a section?)
In a chronology, you'd be more likely to see the simple present tense:
The soil material is rejected for dumping
or the past tense:
The soil material was rejected for dumping
or, with "the" and "be" elided:
soil material rejected for dumping
You should choose either present or past tense for your whole chronology, and stick to it.
The last option I presented, with "the" and "be" elided, isn't a full, grammatically correct sentence, but I believe it's the most common way to write these things.