Res 2003-152 - Laserfiche WebLink

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VOW upper walls, graded to slope and re- vegetated with riparian woodland species. The second site is located in Rio Vista Park (Enclosure 7, Photo 14). Approximately 1800 cubic feet of concrete debris will be removed, graded to slope and re- vegetated with native bottomland hardwood species. Approximately 4000 cubic feet of concrete will be removed from a building foundation and railroad debris located along the west bank of the river, south of the railroad crossing. The San Marcos River diversion spillway (Enclosure 7, Photo 1 6) located just upstream from the Rio Vista Dam diverts a small amount of flow under Cheatham Street and through a concrete vault that was once part of a gristmill built in the late 1800s (Enclosure 7, Photo 17). The concrete vault currently impedes flow to the Crooks Oxbow area, collects litter and creates stagnant water behind the structure (Enclosure 7, Photo 18). The removal of the headwall within the vault would increase the flow of water from the diversion spillway to the Crooks oxbow area located downstream. Approximately 5 000 cubic feet of concrete will need to be removed within the area. Due to the possibility of cultural and historical significance associated with the structure, an assessment by a certified cultural resource specialist will be required prior to including this measure in the final restoration plan. (7) River Bank Stabilization: The lack of riparian corridor vegetation and associated recreational use have promoted riverbank erosion at several locations within the project area (Enclosure 7, Photos 19 -21 ). Identified areas are located above and below Purgatory Creek, within City Park, below the Rio Vista Dam and within Lucio Park. The majority of the erosion within these areas is due to the loading and unloading of equipment and floatation devices associated with recreational use. Approximately 9000 square feet of riverbank will need to be stabilized and re- graded within the project area. The use of gabions or concrete bags will be used to establish a hard toe at the base of the eroded bank. Above the hard toe, native vegetation with extensive root systems, such as deer muhly grass, elbow bush, coralberry, black willow and bald cypress, will be used to stabilize the riverbank. Installation of permanent docking and access points (outlined in measure 10) along the river will also help protect newly planted vegetation and minimize riverbank erosion associated with recreational use. The area located underneath Hopkins Street Bridge (Enclosure 7, Photo 7) is an example of an area that receives a large amount of street runoff and as a result of being constantly shaded by the bridge has little vegetation to reduce erosion. The City of San Marcos would like to install native cobble or riprap in areas such as this to promote bank stabilization, reduce erosion and minimize the deposition of sediment into the river. Approximately 2100 square feet of riprap will be required for the proposed restoration project. The use of vines and mid - grass species that are shade tolerant may also be utilized in such areas. (8) Wetland Enhancement & Creation: Three areas have been identified as potential locations for wetland enhancement and creation. Creation of emergent wetland areas within the project area will increase habitat biodiversity, help process polluted runoff and improve water quality within the San Marcos River. The first site is located south of Hopkins Street on the east side of the San Marcos River and the Hopkins Street Bridge (Enclosure 7, Photo 22). The existing structure consists of a storm water drainage ditch and associated culverts leading into the San Marcos River. The area II