According to the Washington Department of Fish and Wildlife, this entire 745 acre site is a "unique habitat matrix" containing wetlands, riparian wetlands, native outwash prairie and oak woodland habitat which house and feed many different species, some of which are endangered or threatened. Read the full in-depth 2016 report on the importance of the property by the Wash. Dept. of Fish & Wildlife.
There are only 3% of native outwash prairies remaining in Washington State. Native outwash prairie is defined as “open areas of excessively drained soil…greater than five acres in size that are covered with native drought-resistant species of grasses, lichens, mosses and forbs. The topography may be flat or mounded.” [TCC Chapter 17.15 Table 8]
Native outwash prairie is an extremely rare and endangered habitat with only 20 extant areas in the world. It is protected as an “important habitat” by the Thurston County Critical Areas Ordinance (CAO). [TCC 17.15.700] There is a portion of native outwash prairie located in the northeastern boundary of the site, bounded by the railroad on the north.
This site is one of only two remaining sites in the Puget Trough that has been known to support all prairie “specialist” butterflies including the state endangered and federal “candidate” species, Taylor’s (or Whulge) Checkerspot, and Mardon Skipper (as identified by the Washington Department of Fish and Wildlife.) The butterflies identified as inhabiting the property generally tend to inhabit the native outwash prairie areas and use native plants as host and nectar plants. Unlike other butterfly species that relocate during their life-cycle stages, the species listed below live out their full life cycle on this prairie.
Water Howellia, a state and federally endangered plant -- an aquatic, winter annual with submerged and floating stems -- is found in wetlands that typically flood from snow melts and spring rains and dry out during the growing season. Water Howellia plants were found in shallow margins around the edges of some of the property’s wetlands.
The site also supports the state endangered Oregon spotted frog and Olympic mudminnow, several state candidate species, including the Puget blue butterfly and the Oregon vespar sparrow, and the state sensitive white top aster The property is considered prime habitat for the federally endangered Golden Paintbrush and the bald eagle, and has been assessed as an excellent re-introduction site for the Mazama pocket gopher and the state endangered western pond turtle and streaked horn lark.
Two salmon-bearing streams, Beaver Creek and Allen Creek, run through the property. The Port’s portion is the headwaters for these streams which support the Black River Watershed. (See Water/Headwaters of Salmon-Bearing Streams )
Three stands of Oregon White Oak woodlands are found on the property in the north central, southwestern and eastern part.
Endangered, Sensitive, or Threatened Species of Rocky Prairie
The species list, below, is available in a printer-friendly version. It was compiled from the sources noted. WDFW suspects rare plant species exist that have not yet been classified on the site.
1. Prairie Specialist Butterflies – According to the Washington Department of Fish and Wildlife (WDFW), West Rocky Prairie is one of only two remaining sites in the Puget Trough that has been known to support all of the prairie specialist butterflies (and an incredible 45 of the 53 Thurston County species of butterflies) including:
- Taylor’s (or Whulge) Checkerspot – federal candidate & state endangered
- Mardon Skipper – federal candidate & state endangered
- Valley Silverspot – federal species of concern (FSC) & state candidate
- Puget Blue – state candidate
- Sonora Skipper – state CWCS*: species of greatest conservation need (SGCN)
- Oregon Branded Skipper – SGCN
- Coastal Woodland Skipper
- Juba Skipper
- Dunn Skipper
- The oak specialist, Propertius’ Duskywing – SGCN
2. Olympic Mudminnow – state endangered – “The extensive wetland riparian complex supports 1 of 3 known populations of the endangered Oregon spotted frog and the Olympic mudminnow.”
3. Oregon Spotted Frog – federal candidate & state endangered – Identified on adjoining WDFW property, and assumed to be in the wetlands and streams on the Port of Tacoma property.
4. Oregon Vespar Sparrow – FSC & state candidate
5. White Top Aster – state sensitive
6. Water Howellia – federally and state endangered – This water plant was found on the adjoining southern property owned by WDFW. In all probability, the plant exists on the Port of Tacoma property though it has not yet been confirmed. The same is true for any of the “water related” species listed.
7. Oregon Oak Woodlands – Three areas are on, or bordering, the Port of Tacoma property contain rare Oregon Oak Woodlands.
8. Bull Trout (federally threatened & state candidate), Cutt-throat Trout and Coho Salmon – WDFW indicated a high probability of these in the streams located immediately adjacent to Port’s property. Residents confirmed.
9. Native Outwash Prairie and Wetlands – Both are located on the Port of Tacoma property. There are only 3% of native prairie lands remaining in Washington.
10. Bald Eagles – Rocky Prairie is an excellent hunting ground for this species.
11. Rocky Prairie has been assessed as an excellent site for the reintroduction of: The federally endangered Golden Paintbrush; the federal candidate & state threatened Mazama Pocket Gopher; the FSC & state endangered Western Pond Turtle; the federal candidate & state endangered Streaked Horn Lark; and the FSC & state threatened Western Gray Squirrel.
Rocky Prairie “represents one of the last opportunities to protect a large piece of functioning prairie/oak/wetland landscape in the Puget Trough and is one of only about 5 remaining high quality examples of glacial outwash prairie landscapes.”
*CWCS: Comprehensive Wildlife Conservation Strategy
WA State Department of Fish and Wildlife
Thurston County Development Services, Planning and Environmental Section & Report
Thurston County Hearing Examiners Report
Re-Issuance Of Mitigated Determination Of Non-Significance
Washington Department of Natural Resources