A horizontal directional drill burrowed through the earth beneath the rushing tides at the mouth of the Bolinas Lagoon on Monday, directed by employees for a small West Marin cable company with big dreams of bringing broadband internet to Bolinas. 

The news of Horizon Cable’s activities, which were aided by a boring contractor, came as a surprise to the Bolinas Community Public Utility District, which has backed plans by a different company, Inyo Networks, to…