The Stony Brook Office Park, located in Waltham, MA, abuts City of Cambridge-owned water supply land. Before the project, the office park's parking lots and driveways drained uncontrolled down a steep slope to the Stony Brook Reservoir, the second of the three in-series water supply reservoirs in the Cambridge water supply system.
Although meeting the standards of the time, the drainage infrastructure did not treat, nor control runoff to today's stormwater standards. Concerns over slope erosion, reservoir sedimentation, and stormwater quality drove the watershed division to request immediate retrofits to protect and improve reservoir water quality. Recognizing the impacts that run-off from the property’s parking areas had on the water supply and reservation land, the property owner, Clarion Partners, and its property management representative, CBRE New England, undertook steps to improve the water quality and control the run-off leaving the site.
The owner/property management team retained the services of John G. Crowe Associates, Inc., civil engineers and landscape architects of Winchester, to assess current conditions and develop an implementable plan to improve the site. The primary goals of the storm water management redevelopment plan were as follows:
- Redesign the property’s site improvements where possible, to increase, protect, and preserve natural vegetation, reduce impervious surfaces, even minimally if possible, to slow down times of concentration, and reduce runoff;
- Provide source controls, pollution prevention, and construction period erosion and sediment control: Introduce and implement nonstructural measures to prevent pollution or control it at its source; and
- Incorporate into the redevelopment plan structural stormwater "Best Management Practices" (BMPs). Design, construct and maintain structural BMPs to attenuate peak flows, to capture and treat runoff, and to provide recharge to groundwater to the extent the soils are capable.
The storm water design for the site minimized disturbance to the parking lots, maintained existing grades inside parking lots and on adjacent slopes. Installation of erosion and sedimentation controls consisting of silt fence, straw bales and straw wattles down gradient of the construction area further minimized disturbance of existing conditions.,
New vertical granite curb was installed along the entire length of the existing parking adjacent to the Reservation to contain surface run-off and direct it to new and existing catch basins. Some of the new catch basins were designed as water quality proprietary storm water units and velocity reducers to treat the storm water run-off. The storm water structures were then connected to several underground perforated pipe storage and recharge trenches to infiltrate the treated runoff and allow the larger storm events to overflow into underground crushed stone level spreaders day lighting out to existing grade conditions along the length of the adjacent Reservation land. The design and construction of the new storm water drainage system has resulted in the significant reduction of erosion and sedimentation onto the Reservation land while still maintaining existing drainage patterns and has dramatically improved the water quality of the run-off discharging from the site towards the Reservation.
Beyond the storm water improvements now in place, the owner and property management team have committed to incorporate environmentally sensitive winter deicing and landscape maintenance practices that will further protect the Reservation land and water supply.