Washington Administrative Code › Title 173 - Ecology, Department of (See also Titles 197, 317, 372, and 508) › Chapter 173-183 - Preassessment screening and oil spill compensation schedule regulations › COMPENSATION SCHEDULE FOR SPILLS INTO FRESHWATER STREAMS, RIVERS, AND LAKES › Section 173-183-620 - Habitat index

Current through Register Vol. 24-14, July 15, 2024
(1) Most state
				freshwaters vary to some degree from the natural condition as increased
				activities within individual watersheds have decreased stream, river, and/or
				lake habitat quality. In order to account for that degradation prior to
				assessing damages using the compensation schedule, a habitat index (HI) is
				calculated to represent existing stream conditions prior to the oil
				spill.
(2) For each stream, river,
				or lake impacted by an oil spill where the preassessment screening committee
				determines that the compensation schedule shall be used, a habitat index (HI)
				shall be calculated following an oil spill using the following methodology. The
				HI measures the amount of stream degradation from natural conditions and shall
				be calculated using the following formula:
Habitat Index (HI) =
				  [(P1+P2+P3+P4+P5+P6)Ã·Np]
				  x f1 x f2 x
				  f3
where:
P1 = barriers to natural
								fish movement
P2 = urbanization
P3 = condition of riparian
								vegetation
P4 = condition of flood
								plain
P5 = land use of
								watershed
P6 = flow alteration
Np = number of P parameters
								used to calculate HI
f1 = channel
								modifications
f2 = impoundment
f3 = water quality
(3)
				The RDA committee shall determine which of the habitat quality parameters
				described in subsection (2) of this section are applicable to the particular
				spill under consideration. If a parameter is not applicable to the spill under
				consideration, the parameter shall not be included in the formula provided in
				subsection (2) of this section.
(4)
				Habitat quality parameters (P).
(a) Barriers
				to natural fish movement (P1). Barriers, to some degree,
				limit the free passage of fish upstream thus limiting the ability of streams to
				recover. The scoring of this parameter is based on the influence of barriers in
				the natural dispersal of fish populations as follows:
Table 12. Scoring of Barriers to Natural Fish Movement
				  (P1).
RATING QUALIFICATION
10
No manmade obstructions to free upstream passage of
								fish
8
No dams or other structures causing a vertical drop
								of more than 1 foot during low flow
5
No dams or other structures causing a vertical drop
								of more than 3 foot during low flow
3
No dams or other structures causing a vertical drop
								of more than 10 foot during low flow
0
One to several dams or other structures each
								causing a drop of more than 10 feet during low flow
(b)
				Urbanization (P2). Urban development has historically
				had negative habitat effects on freshwater ecosystems. The percent of urban
				development in a watershed directly influences siltation, riparian abuse, and
				water quality deterioration. The scoring of this parameter is based on the
				percent of urbanization in the stream watershed.
Table 13. Scoring of Urbanization
				  (P2).
RATING QUALIFICATION
10
Less than 5 percent of the watershed in urban
								development
8
Five to 10 percent of the watershed in urban
								development
5
Ten to 40 percent of the watershed in urban
								development
3
Forty to 70 percent of the watershed in urban
								development
0
Seventy to 100 percent of the watershed in urban
								development
(c)
				Condition of riparian vegetation (P3). Riparian
				vegetation is important to seventy percent of the animal and bird species in
				Washington for some part of their life cycle. It also exerts thermal regulatory
				and thermal controls for the aquatic system. The scoring of this parameter is
				based on the percent of banks that are protected by effective riparian
				vegetation.
Table 14. Scoring of Condition of Riparian Vegetation
				  (P3).
RATING QUALIFICATION
10
Ninety to 100 percent of the banks are protected by
								appropriate perennial vegetation
8
Sixty to 90 percent of the banks are protected by
								appropriate perennial vegetation
5
Forty to 60 percent of the banks are protected by
								appropriate perennial vegetation
3
Ten to 40 percent of the banks are protected by
								appropriate perennial vegetation
0
Zero to 10 percent of the banks are protected by
								appropriate perennial vegetation
(d)
				Condition of the flood plain (P4). The condition of the
				flood plain forecasts the amount of sedimentation and erosion in the watershed
				and as such is a primary predictor of stream degradation. The rating of this
				parameter is as follows:
Table 15. Scoring of the Condition of the Flood Plain
				  (P4).
RATING QUALIFICATION
10
Little or no evidence of active or recent erosion
								of the flood plain during floods
5
All segments show evidence of occasional erosion of
								the flood plain. Stream channel essentially intact
0
Flood plain severely eroded and degraded, stream
								channel poorly defined with much lateral erosion and much reduced flow
								capacity
(e)
				Land use of the watershed (P5). Land use practices exert
				a great deal of influence on the quality of the aquatic habitat. The rating of
				this parameter is as follows:
Table 16. Scoring of Land Use of the Watershed
				  (P5).
RATING QUALIFICATION
10
More than 80 percent of the watershed protected by
								timber, improved pasture, terraces, or other conservation practices
8
Sixty to 80 percent of the watershed protected by
								timber, improved pasture, terraces, or other conservation practices
5
Forty to 60 percent of the watershed protected by
								timber, improved pasture, terraces, or other conservation practices
3
Twenty to 40 percent of the watershed protected by
								timber, improved pasture, terraces, or other conservation practices
1
Zero to 20 percent of the watershed protected by
								timber, improved pasture, terraces, or other conservation practices
(f)
				Flow alteration (P6). Alteration of the natural flow
				regime can frequently alter habitat conditions that are necessary for certain
				behavioral and ecological needs of species. The rating of this parameter is as
				follows:
Table 17. Scoring for Flow Alteration
				  (P6).
RATING QUALIFICATION
10
Less than 1 percent of the watershed controlled by
								impoundments and/or less than 50 percent of the watershed controlled by farm
								ponds
8
One to 30 percent of the watershed controlled by
								impoundments and/or less than 50 percent of the watershed controlled by farm
								ponds
5
Thirty to 60 percent of the watershed controlled by
								impoundments and/or less than 50 percent of the watershed controlled by farm
								ponds
3
Sixty to 95 percent of the watershed controlled by
								impoundments and/or less than 50 percent of the watershed controlled by farm
								ponds
0
Ninety-five to 100 percent of the watershed
								controlled by impoundments and/or less than 50 percent of the watershed
								controlled by farm ponds