WATER RESOURCES AND WETLANDS 3.6 WATER RESOURCES AND WETLANDS 3.6.1 Environmental Setting 1) Master Plan and Urban Renewal Plan There are two significant bodies of water associated with the proposed project area. The first, the Saw Mill River (Nepperhan River), is the primary surface water feature providing drainage for the portion of the City of Yonkers containing the Project Area. The watershed is 20 miles long, extending into twelve municipalities between the headwaters in the hamlet of Chappaqua in the Town of New Castle, to the mouth of the river at Yonkers. The total size of the drainage basin is estimated to be 24.0 square miles. The Saw Mill River in the URA area is a narrow channel contained by 2 four-foot wide, vertical, concrete bulkhead walls. The New York State Department of Environmental Conservation (NYS DEC) inspects the site annually while the City of Yonkers is responsible for the river’s maintenance. The river has been designated as a Federal Navigable Waterway by the United States Army Corps of Engineers (USACOE) and is therefore subject to federal navigational servitude, the right of the federal government to regulate navigation and to prevent the obstruction of navigation. Therefore, the public has the right of navigation, including the right to use the surface. However, because the width of the channeled river at its widest point within the project area is less than 15 feet, the waterway is generally not used for transport. The Saw Mill River in the area is neither easily accessible nor readily visible to the public. The second body of water, the Hudson River, is located approximately 2,500 feet west of the project area. HOPE VI sites within the project area are located at an elevation of greater than 90 feet above the Hudson River, which is a sea level, tidal estuary where it borders Yonkers. The oOverall the project area is located in a highly developed urban area, and does not contain any DEC, USACOE US Army Corp of Engineers or locally regulated wetlands. The project area is mostly fully paved (with exception to the Old Croton Aqueduct) and consists of impervious surfaces and vacant but re- vegetated land. Stormwater runoff leaves the paved areas as surface runoff into municipal storm basins, which are receptors for the city sewer system. The limited portions of vegetated or landscaped grounds allow for some stormwater to infiltrate into the ground. ASHBURTON AVENUE/ MULFORD GARDENS FEIS February 2006 Page 3.6-1 WATER RESOURCES AND WETLANDS 2) Mulford Gardens Hope VI Plan A. Mulford Gardens HOPE VI Sections A, B, C 1. Project Site Saw Mill River (Nepperhan River) The Saw Mill River, known as the Nepperhan River over its lower reach in Yonkers, is the primary surface water feature providing drainage for the area of the City of Yonkers that encompasses the Hope VI revitalization project and the proposed Urban Renewal Area (URA). The watershed is 20 miles long, extending into twelve municipalities between the headwaters in the hamlet of Chappaqua (Town of New Castle), to the mouth of the river at Yonkers. The total size of the drainage basin is estimated to be 24.0 square miles by the United States Geologic Service (USGS). The names of the river were derived from its early uses. The Algonquian-speaking Lenape Indians called the lower reach "Nappeckamack," or "trap fishing place," because fish were so plentiful in this area of the Nepperhan ("Trap") River. In 1646, Dutchman Adriaen van der Donck obtained a grant for the region from the Dutch West India Company, secured the title by purchasing the land from the Indians, and built a sawmill on the river. The Nepperhan River has since become more commonly known as the Saw Mill River. Since the earliest part of the last century, much of the downstream section of the river has been bulkheaded or riprapped into an approximately 20 foot wide channel. Much of this work was conducted by the United States Army Corps of Engineers (USACOE) to control overbank flooding. The lowermost section was diverted to culverts to carry the river underneath the City of Yonkers. Recently, the concept of “daylighting” this lower-most section of the river has been proposed by the City. Grants totaling $65,000 have been raised for studying the ecology of the river, including the engineering feasibility of a “daylighting” project. The Saw Mill River in this area is a narrow channel contained by bulkhead. It is designated as a Federal Navigable Waterway. The use of navigable waterways is subject to federal navigational servitude. Therefore, the public has the right of navigation, including the right to use the surface. A mapped FEMA floodplain is associated with this reach of the Saw Mill River. When the Army Corps of Engineers did work on the Saw Mill River related to the flooding, they turned over jurisdiction to DEC, which then transferred maintenance responsibility to the City of Yonkers. The DEC inspects the site on an annual basis and the City conducts maintenance. According to the City of Yonkers Engineer’s ASHBURTON AVENUE/ MULFORD GARDENS FEIS February 2006 Page 3.6-2 WATER RESOURCES AND WETLANDS Office, A Floodplain Easement on the eastern edge of HOPE VI Section C prohibits construction of structures, including buildings or retaining walls, in this area so that access to the river for maintenance purposes can be maintained (Richard Morris, telephone discussion, August 24, 2005). The HOPE VI Sections and the overall Urban Renewal Area are located in a highly developed urban area. Review of State and federal wetlands mapping confirms that there are no New York State Department of Environmental Conservation (NYS DEC), USACOE or locally regulated wetlands within the project area. The Saw Mill River is a receptor for surface water runoff from the subject HOPE VI Sections. The Saw Mill River below the Yonkers water supply dam (located 1.3 miles south of the City Line between Yonkers and the Town of Greenburgh) is rated as a Class D water body by the NYS DEC (NYS Code Part §701.9), indicating that the river is suitable for fish survival but not for propagation of fishes. Factors such as intermittency of water flow or condition of the streambed may exist that prevent the propagation of fishes in the river. Class D waters are also suitable for primary and secondary contact recreation although other factors, such as accessibility or stream flows or depths, may limit their use for these purposes. Generally, the Saw Mill River is neither accessible nor readily visible to the public. Activities within the Saw Mill River would be regulated by the Army Corps of Engineers, due to its status as a “water of the United States”. The USGS maintained a streamflow monitoring gage station (USGS Station #01376500) on the Saw Mill River from 1944-2003. The station was located approximately 100 feet downstream of the Ashburton Avenue bridge across the river. Since 2003, the station has been inactive. Average annual river flows measured at the USGS station have ranged from 12.5 cubic feet per second (cfs) to 65.3 cfs over the period of record keeping. The mean annual river flow over the period of measurement was 33.2 cfs. Peak annual river flows, representing the greatest storm water runoff event for each year, have ranged from 265 cfs to 1450 cfs over the period of record keeping. The historic peak flow occurred on September 16, 1999, following the passage of Tropical Storm Floyd. The mean annual peak flow over the period of measurement was 595 cfs. The Hudson River is located approximately 2,500 feet west of the Urban Renewal Area. HOPE VI sites within the URA are located at an elevation of greater than 90 feet above the Hudson River, which is a sea level, tidal estuary where it borders Yonkers. As described above, one of the HOPE VI Sections (Section C) is located within the 100 year flood plain, according to Federal Emergency Management Administration (FEMA) maps (Figure 3.6-1). ASHBURTON AVENUE/ MULFORD GARDENS FEIS February 2006 Page 3.6-3 Project Area Source: FEMA 0 1000 2000 ft Figure 3.6-1: FLOOD MAP ASHBURTON AVENUE/MULFORD GARDENS FEIS WATER RESOURCES AND WETLANDS Section A Section A on Ashburton Avenue consists of vacant but re-vegetated land. There are no wetlands on the Section and stormwater collected by the site either infiltrates into the ground or leaves the site as surface runoff to adjacent lots, including the area of the Old Croton Aqueduct Trailway. Section B Section B is fully paved and consists entirely of the impervious surfaces of an existing parking lot. Stormwater runoff leaves the site as surface runoff into adjacent municipal storm basins, which are receptors for the city sewer system. Section C Section C consists of vacant but re-vegetated land that is used as a community garden. The eastern boundary of Section C is comprised of a four-foot concrete wall abutting the Saw Mill River. There is a 10- to 25-foot wide permanent easement on the site abutting the Saw Mill River. This easement is granted to the New York State Department of Environmental Conservation for the acquisition of property for the Yonkers Flood Protection Project II. As stated above, access to the river for maintenance purposes is ensured through an easement that prohibits construction within area proximate tot he river. There are no wetlands within Section C, and stormwater collected by the site either infiltrates into the ground or enters the adjacent municipal storm basins. 3.6.2 Potential Impacts 1) Master Plan and Urban Renewal Plan One potential future action contained within the Master/Urban Renewal Plans is the widening of Ashburton Avenue; this specific action may include the widening of a bridge across Ashburton Avenue between Nepperhan Avenue and Saw Mill River Road.