The New York State Public Service Commission (PSC) on Jan. 3 said that it seeking comments on Hudson Transmission Partners’ (HTP) petition requesting an amendment to its certificate of environmental compatibility and public need for the company’s 345-kV submarine/underground electric transmission line between Manhattan and New Jersey.
As TransmissionHub reported, HTP’s approximately $850m HVDC line between Ridgefield, N.J., and Manhattan began delivering power to New York City customers in June 2013.
The PSC, in its Jan. 3 notice, said that HTP’s petition seeks approval to use mechanical dredging during in-river cable maintenance, repair and replacement operations in addition to its existing authority to use mechanical dredging in the installation of the cofferdam and in related land-to-river transition operations.
All comments should be submitted to the PSC secretary by Jan. 10, the PSC said.
According to HTP’s filing dated Dec. 30, 2016, the HTP cable – which consists of three conductor phases and two fiber optic communication lines bundled together – last November experienced a fault in one of its three phases.
The location of the fault has been identified as being in New York waters approximately opposite West 90th Street in Manhattan where the cable is buried 10-15 feet below the river bed in a part of the Hudson River that experiences powerful currents and is subject to tidal forces making the exclusive use of jetting a more time-consuming process and posing greater risks to divers, the company said.
Repairing the faulted phase will require locating the fault, removing a section of the conductor containing the area damaged by the fault and sealing both ends of the undamaged sections of the conductor before proceeding to a permanent repair, the company said.
HTP said that the amendment it is applying for would grant the company authority to employ mechanical dredging to expedite the operation. The ability to use mechanical dredging in that operation would expedite the process and greatly enhance divers’ safety by reducing their time in the river and the amount of sediment they would need to excavate, the company said.
The HTP cable was installed using jet plow technology for most of its Hudson River route, and at the locations where the submarine cable transitioned from river to land, installation required additional activities, including mechanical dredging. Similar to, but potentially more complex than, those activities, maintenance, repair, and replacement operations may require the removal of large quantities of sediment lying over the buried cable, HTP added.
Mechanical dredging enables the removal of large quantities of sediment over-burden even during periods when river currents are a factor, HTP said. In contrast, reliance on jetting technologies, which in the case of repair operations are limited to hand, diver-implemented, jetting, limits activities to the approximately one-hour intervals of slack tide experienced on average four times in each 24-hour period, HTP said. By using mechanical dredging in conjunction with hand jetting, the repair or replacement operation can be completed in far less time, the company said.
According to HTP, work is anticipated to begin in mid-January, and to last about 30 days.