“We are honored by the recognition awarded to MDM Consulting Engineers by ACEC New York. Our aim in designing mechanical, plumbing, electrical, and safety systems for the DSNY garage facilities was to provide the sanitation personnel with a healthy and safe workplace,” said MDM Principal Mariano D. Molina. “MDM has served the New York City Department of Sanitation as an engineering and design consultant for 30 years and we look forward to continuing this relationship by providing innovative and economical engineering solutions.”
MDM served as mechanical, electrical, plumbing, and fire protection engineering, design, and construction services consultant for the 235,000-square-foot project, located at 137-157 Varick Ave. in Brooklyn. Two buildings that comprise the project are situated along a common service road and house sanitation vehicle garages and maintenance facilities for the Brooklyn Community Districts 1 and 4, as well as the DSNY Brooklyn Borough administrative offices. These buildings also accommodate employee facilities, a salt storage shed, and a parking facility.
Vehicular and pedestrian traffic circulation through the site and buildings is designed to facilitate the movement of large numbers of trucks through the garages, while maintaining access to repair bays. Sanitation vehicles drive down the service road to access rear entrances of both garages. Once inside the garages, the trucks are stored, fueled, washed, and repaired for the next day’s run.
Dozens of garbage trucks are stored next to each other and drivers start the engines at approximately the same time at the beginning of each workday. The truck engines emit a high volume of air pollutants, which must be rapidly removed from the building to maintain a healthy and comfortable environment for truck operators and other personnel. The garbage trucks also emit strong odors.
DESIGNThe heating and ventilation (HV) system design called for the induction of clean air at locations where personnel occupy the garages, and for removal of contaminated air away from the employees and near the areas where the emissions are produced. The system also encompasses air conditioning equipment that serves the office areas.
The MDM team’s design focused not only on meeting the client’s performance requirements, but also on minimizing energy use and simplifying the system’s components, operation, and maintenance. At the client’s request, the team avoided specifying overly complex and costly components, such as heat recovery features or fully automated control systems.
According to Molina, “During the design research phase, MDM defined four modes of the garage operation that called for different settings of the HV system. The modes vary depending on the occupancy levels, presence or absence of running engines, and the quality of the indoor air. For each mode of the garage operation, there is a dedicated system setting that provides required environmental conditions while minimizing energy use. This approach reduced both the first cost of the system and the energy consumption.”
MDM applied a computerized airflow design program to optimize the volume and location of the fresh air induction and exhaust discharge points. The computer program also ensured the adherence of the system design and air quality with OSHA and New York City building codes and regulations.
To simplify the HVAC system and its controls, MDM included CO monitors that sound an alarm when the CO level exceeds the safe limit. As required by the client, the response to the alarm is not automated but, instead, the garage director of operations controls the ventilation system manually. The DSNY requested this type of control in order to avoid a potentially unreliable or unnecessarily complex automated system.
The system consists of relatively simple and low-maintenance supply and exhaust fans that operate at different air exchange volumes, depending on the garage operation mode. The system has the following four operational settings.
1.Garage operation mode: not occupied. HV system setting: all HV units are off and unit heaters heat the buildings.
2.Garage operation mode: occupied, but all truck engines are off. HV system setting: all HV units are off and exhaust fans operate at half speed, providing 1.5 air exchanges per hour. The heaters are on, if necessary, to maintain comfortable temperature inside the garage.
3.Garage operation mode: occupied and truck engines are on. HV system setting: all HV units are turned on and exhaust fans operate at full speed providing 6 air changes/hour. The heaters are on, if necessary, to maintain comfortable temperature inside the garage.
4.Garage operation mode: occupied, truck engines are on, and emissions exceed safe settings at one or more locations within the garage. HV system setting: all HV units are turned on and exhaust fans operate at full speed. In addition, the emergency fans are turned on and wall louvers are opened to remove an additional 6 air changes/hour of contaminated air (12 air changes total), unit heaters are turned on, if necessary, to maintain the desired temperature within the garage.
MDM’s relationship with the New York City Department of Sanitation began in 1978, under a comprehensive Department of Sanitation garage and maintenance facility modernization program. The modernization program was a result of a record snowstorm and low temperatures that prevented DSNY plow truck diesel engines from starting inside the garages. Most of the DSNY facilities at that time were not heated or ventilated. The department retained MDM to evaluate the adequacy of the MEP systems serving DSNY facilities throughout New York City.
Founded in 1978, MDM has grown to its present staff of approximately 70 engineers, technical personnel, and support staff. The firm has offices in New York City and Jersey City, N.J.