Initial Study MND - Sonoma County Agricultural Preservation and ...

Taylor MountainINITIAL STUDY/MITIGATED NEGATIVE DECLARATIONPrevention Plan (SWPPP) that includes detailed erosion and sedimentation controls and BMPsfor controlling runoff, construction practices, vehicle fueling and maintenance and othermeasures to protect water quality (Master Plan Standard 141).Operation of the Preserve would have the potential to result in impacts on water quality due torun off. Operation of private vehicles on the site could result in the deposition of oil and greaseon surface parking lots that could subsequently be carried to surface water on the site.Impervious surfaces could result in increased runoff. However, the amount of impervious areawould be very limited, as the staging areas would be primarily unpaved pervious surfaces, asshown on the Master Plan conceptual design figures. Staging areas and visitor developmentwould contain features to achieve Low Impact Development (LID), as required by theNCRWQCB MS4 Permit. These design features would capture onsite runoff and preventincreased discharge to nearby water sources. Reuse of the existing bathhouse would furtherlimit the amount of new impervious features.The proposed project would allow hikers, bicyclists and equestrians to use Taylor Mountain ona regular basis. While equestrian use and dogs would result in some additional urine and fecesbeing deposited on the site, park information would emphasize minimizing the amount of urineand fecal matter that enters the drainage. Any potential increase would not be substantial inrelation to the existing use of the site for cattle grazing.One of the Master Plan’s objectives is to protect upland hydrology to maintain existingstormwater and sediment delivery levels to creeks. The Master Plan includes numerousstandards to minimize erosion and sedimentation during construction and operation,summarized as follows: S21 – Utilize Low Impact Development (LID) techniques in landscaped or other developedareas, as required by the NCRWQCB MS4 Permit and as specified in the in the Storm WaterLow Impact Design (LID) Technical Design Manual, to intercept flows and allow water topercolate into soil and reduce sediment delivery. S26 and S66 – Maintain vegetated buffers from creeks. (Table 3 in the Master Plan listsbuffer requirements for various types of proposed development.) S37 – Locate new trails well away from headcuts. S44 – Site new trails at least 500’ from the existing freshwater pond. S86 – Avoid and minimize erosion in trail routing and construction. S87 – Use full bench construction for trails where feasible. This means the full tread width issupported by undisturbed soil without the need for fill on the downhill side. This techniqueresults in more stable trails that are less susceptible to erosion. S93 – Use rolling dips to direct water off the trail for minor seasonal drainage crossings and atappropriate intervals based on trail slope. S94 – Use armored rolling dips at moderate seasonal drainage crossings to minimize erosionand sediment impacts and provide all weather access for trail users.September 2012 B-83 Final