Estuarine, intertidal, hardpan, partly enclosed, eulittoral

Areas of hardpan are common in Puget Sound, yet few surveys have been done. Hardpan is resistant basal till, composed of poorly sorted but well compacted glacial deposits often including clays. Hardpan shelf habitat may be seen in the mid-low intertidal and often has pockets of sand overlying it. The hardpan tends to erode more readily than bedrock and thus does not harbor as many long-lived species, but does contain some unusual organisms such as boring clams and the other species that live in their burrows.

Habitat attributes

Class ID: 
Class name: 
Estuarine, intertidal, hardpan, partly enclosed, eulittoral
70.0 km (in WA)
Primary substrate: 
Secondary substrate: 
Tertiary substrate: 
Substrate stability: 
Substrate key details: 
Semi-solid rock, some overlying sand
Wave exposure: 
Blue book classes: 
Estuarine intertidal hardpan: Open
Map/survey site examples: 
Alki Point (in part), much of Harstine Island, parts of Tacoma Narrows
Fish sampling sites: 
Diagnostic species: 
  • Petricolaria pholadiformis
  • Zirfaea pilsbryi
  • Boccardia proboscidea
  • Balanus glandula
Species notes: