Draft EIS/EIR for the San Luis Reservoir SRA Resource ...

5. Environmental Analysis
operation of these new facilities could result in minor changes in drainage
patterns and runoff quantities, but adverse effects would remain minor and
short-term. Overall, Alternative 3 would have greater effects on water
quality than Alternatives 1 and 2 but less than Alternative 4. Effects would
be minimized to minor levels through implementation of the trails
management plan and measures such as those described in Section 5.4.1.4.
• Alternative 4 includes two new trails, which would link Basalt Use Area
with Dinosaur Point Use Area and Los Banos Creek Use Area with Basalt
Use Area. Otherwise, trails and roads and the associated impacts from
construction and use would be identical to Alternative 3. Construction of
trails through currently undeveloped areas, including privately owned land
between the two parts of the Plan Area, would have the potential for minor
to major adverse effects. These effects would be minimized to minor
levels through implementation of the trails management plan and other
measures such as those described in Section 5.4.1.4. Effects would be
minimized to minor levels through implementation of the trails
management plan and measures such as those described in Section 5.4.1.4.
Motorized Vessel Emissions Any release of fuel or other pollutants from a
motorized vessel has the potential to affect Plan Area water quality. Some
personal watercraft and fishing boats with outboard motors have carbureted twostroke
engines (nonconformant engines) that release an unburned fuel mixture
from the engine directly into the water. As a result of new emissions regulations,
all recreational marine vessel engines and personal watercraft were required to
have compliant two-stroke (direct injection) or four-stroke engines from 2008
onward (see Sections 2.4.3.3 and 2.5). Almost 50 percent of the remaining
nonconformant two-stroke engines are projected to remain in use by 2012
(Federal Register 1996). No data are available for the percentage of vessels with
nonconformant engines typically present in the Plan Area.
Potential water quality effects from motorized vessel emissions would vary by
alternative as follows:
• Alternative 1, No Action/No Project, would not impose a timed phaseout
of nonconformant two-stroke engines. The duration of nonconformant
engine use in Plan Area waterbodies would be longer in the absence of a
timed phaseout. Water quality data show that no water quality standards
associated with vessel fuel discharges have been exceeded (see Section
2.4.3.2); however, continued use of nonconformant two-stroke engines is
anticipated to have minor adverse impacts on water quality, which would
be greater than with the action alternatives.
• Alternative 2 and the other action alternatives would impose a three-year
phaseout of nonconformant two-stroke engines. During the three-year
phaseout period, continued use of nonconformant two-stroke engines
would have minor adverse impacts on water quality, followed by
beneficial impacts after the phaseout. After the three-year phaseout period,
all recreational marine engines in use in the Plan Area will be required to
5-14 San Luis Reservoir SRA
Draft RMP/GP and Draft EIS/EIR