The Patterson Site Improvements include a new playground (1,917 SF) and turf field (2,174 SF) zone and a rain garden with a stone infiltration storage trench (2513 SF). A performance area has the rain garden as the backdrop, and an outdoor classroom area is nestled into the center of the rain garden. A concrete path and paving (1400 SF) separates the rain garden from the permeable turf field and porous recycled rubber safety surface playground. The site improvements are included in one continuous area of site disturbance that also includes the two asphalt basketball half courts surrounded by a two lane asphalt track (4,115 SF).
The area of disturbance/concrete pavement removal is 13,572 square feet. The Patterson School stormwater management design will retain 2” of stormwater over an 20,110 SF drainage area. The rain garden with its boulders and field stone outdoor classroom will have a 10” stone infiltration bed with 2’-0” of planting soil above.
The rain garden is graded to allow stormwater to pond during a large rain event to a maximum of 6” deep. At the west end of the site, the water from the impervious existing concrete pavement starting at the Holbrook St. Sidewalk edge (elevation 44.61) and the new asphalt basketball court pavement will surface flow towards the playground and turf field which will capture stormwater at a 1:1 rate. All excess water from the playground porous rubber safety surface and the turf field areas will migrate subsurface and, also, surface flow to the rain garden infiltration bed at the east side of the site. The low edge of the rain garden will be at the northeast corner: elevation 41.0. Any extreme storm event that results in more than 2” of stormwater will be managed by overflow piping to the existing sewer main in Holbrook Street on the south side of the site.