I found out through some deep research that my pond was built in 98. It looks to have maybe 3 layers. (Cement, some kind of stuff that looks like insulation and then a black outer to protect everything. I've attached some pictures for everyone to see. I'm curious if anyone knows what exactly is the shell made out of and recommendations for repair. The sides have taken a beating from the weedeaters. Thank you in advance for your suggestions and help.