From Pittsburgh Water (PW):

This week we will begin geotechnical work at the covered Highland Reservoir. The purpose of this work is to collect soil samples to assess and determine the condition of the dam. Community members may notice equipment on site including a drill, tanks, pumps, and hoses. This is related to the dam stabilization project and all we are doing at this time is collecting the necessary samples. If you have any additional questions, please let us know.

From HPCC:

The work described above is related to PW's need to comply with DEP's regulations about dams, which DEP posits are applicable to the reservoirs in Highland Park. It's expected that the regulations would eventually require removing the trees from around both reservoirs. The HPCC would like to protect as many trees as possible and is beginning to have regular meetings with PW, DPW, and Deb Gross' office about this issue and the Pump Station. We'll keep the community posted as things progress.