Environmental Information Document

Project 2009-23

Berwick Water Department

Backup Systems for Emergency Response

Installation of Diesel Electric Power Generator at the Water Treatment Plant

Project Description

Install a 250 kilowatt electric power generator and a fifty-hour-endurance diesel fuel supply at the Water Treatment Plant of the Berwick Water Department so that when electrical power is unavailable from the local grid, the Plant may continue to operate.

The source water of the Berwick Water Department is the SalmonFallsRiver. The Department serves 921 accounts, and a calculated population of 2,300. There is one standpipe, about 13 miles of water mains, and 104 fire hydrants. Its service area is the entire Town of Berwick, with the exception of that part of the Town lying southwesterly of the Guilford Transportation Railroad Tracks at the southwestern boundary of the Town.

Environmental Setting of the Project

The Treatment Plant is at 150 Rochester Street (see Aerial Map), to the northwest of the town center of Berwick. The proposed site of the generator is six feet away from the Plant’s northwest wall, about equidistant from that exterior wall and the Plant’s security fence (see Detail of Generator Site Plan).

The site is within the floodplain of the Salmon Falls River: “the lowland and relatively flat areas adjoining” the river, and “including at a minimum, that area subject to a one percent or greater chance of flooding in any given year” (Executive Order 11988, May 24, 1977). The enclosed FIRM 230144-0006B, dated 5 August 1991, upon which the site is labeled “Project Location” and marked by a black spot drawn inside Zone AE, can be compared with the Aerial Map to confirm that the Project site is within the floodplain.

The site is not within the floodway of the Salmon Falls River: in FIRMs showing the base flood elevation, such as the one enclosed (note the “177” on the finger of Zone AE extending toward the top of the page), the floodway is represented by a cross-hatched area extending outward from the river, in this case defining an area more than 500 feet distant from the site.

Although the enclosed FIRM does depict the site as being in the riverine Special Flood Hazard Area, this is no longer the case. The enclosed FEMA letter of 15 September 1997 is a Letter of Map Amendment executed prior to the construction of the current Water Treatment Plant; it redesignated the Plant;s site into Zone X. The new Digital Flood Insurance Rate Maps show that the Water Treatment Plant and the area immediately surrounding it are in Zone X.

As shown on the FIRM, the base flood elevation is 177. Referencing the enclosed Detail of Generator Site Plan, land at this elevation lies on upwardly sloping land outside the security fence, the fence being at approximately elevation 180. In the lawn area lying between the fence and the Plant’s foundation 22 feet away, where the generator is proposed to be installed, the slowly upwardly sloping ground reaches elevation 181, putting the lowest part of the proposed installation—the bottom of the 12-inch high concrete slab—at about four feet above the base flood level.

If the generator is installed as proposed, the environmental setting will only be changed in a minimal way. Not only is the site already developed, and the generator at an elevation unlikely to be reached by floodwater, but even if it were reached, the volume of floodwater displaced by the generator during a flood reaching elevation 187 would be less than 840 cubic feet, not enough to raise the level of an acre of water by one quarter inch. The environmental setting will be very nearly the same with or without the project.

Alternatives to the Project

The alternatives to the proposed installation of the generator in the floodplain fall into three groups: finding another location where the generator might be sited; developing another way to achieve the purpose of the proposed generator, and abandoning the project.

Alternate Sites

No other site within the floodplain could have less impact on the floodplain than the proposed site, although some others might have a similarly low impact. However, being farther from the Plant, those other floodplain sites would be much more expensive to develop and operate without providing any corresponding benefit.

Any site outside of the floodplain would be at least several hundred feet from the Plant and would be much more expensive to develop and operate. In addition, the minimal reduction in floodplain impact offered by removing the generator from the floodplain would be counterbalanced by the impact created by building flood-safe power transmission facilities adequate to carry high quality 480 volt, three phase, power from the generator to the Plant.

Although it is technically feasible to site the generator at an alternate site, there is no reasonable likelihood that it will produce a lower impact on the floodplain than the proposed site, and the cost would be higher to an unreasonable degree.

Alternate Means

Stated broadly, the purpose of the Project is to provide up to a week of potable water to the Town of Berwick during a period when the local electric power grid is not supplying power to the Water Treatment Plant.

There are, therefore, two branches to the discussion of an alternate means: one, what other ways exist for electric power to be generated at the Water Treatment Plant, and, two, what other ways exist to meet the general need identified in the Project’s purpose.

  1. Wind, solar, and hydroelectric power generation might conceivably be used to provide electricity to the Plant on a daily basis, and, not being fed off the grid, act as “emergency power” at the same time. But there are significant disadvantages: the cost would be somewhere between 25% and 300% higher; the wind generation potential, the available sunlight, and the river velocity at or near the Plant site are all mediocre; any one of these alternate means of generation would require a back-up conventional generation capacity and even by themselves would represent a much more intrusive presence in the floodplain than the proposed generator if they were to provide the large power requirements of the Plant. For these reasons, no other means of electric power generation is considered environmentally, technically, or economically feasible.
  1. Providing a week of average water consumption to the Town when the Plant wasn’t able to produce it would require another source for about 1.085 million gallons. Three options are worth evaluating:
  • Obtain the needed water through the existing interconnection to the Somersworth, New Hampshire Water Department.

An 8-inch main connects the two systems. There is an agreement in force providing for water to be sold to Berwick under emergency conditions. The Somersworth treatment plant has excess capacity, and the Berwick Water Department personnel have a good relationship with the Somersworth personnel.

Unfortunately, substantial problems exist. The two opposing system pressures at the interconnection do not allow flow into the Berwick system until the Berwick standpipe is down to the lowest level that will provide “barely legal” pressure (25 psi) to the residents clustered around the base of the standpipe at the top of Pine Hill. Also, Somersworth employs a free chlorine disinfection residual in the distribution system, while Berwick uses a chloramine residual. Taste and odor issues, as well as regulatory residual issues will be created by the altering of the ammonia/chlorine ratio and the neutralization of the free chlorine as it oxidizes the chloramines compounds. In addition, if there is a grid power failure in Berwick there may be one in Somersworth, too, and in that emergency environment, Somersworth may want to shepherd its resources and run its own emergency generator as little as possible.

For technical reasons, this is not a viable option.

  • Increase the volume of the Department’s Standpipe by 1.085 million gallons.

Our welded steel standpipe holds 1.1 million gallons when full. Doubling the height from 85 to 170 feet, or adding a mushroom top of 30 extra feet with 25 extra feet of diameter would provide the water needed, although significant reinforcement would be required.

Here, again, the problems outweigh the benefit. The age of the water in our current standpipe is a problem, presenting a risk of health problems through nitrification of the chloraminated water and increased disinfection byproducts. With twice the volume, it would be much worse, although, of course, for extra cost, a circulation system could be installed. The cost of the larger standpipe would be a least equal to an entire new million gallon standpipe—on the order of 2 million dollars.

For economic reasons, this is not a feasible option.

  • Construct a booster station at the existing standpipe so that the entire volume of water in the standpipe could be used.

As currently employed, the standpipe is never lowered below 65 feet because the pressure becomes undesirably low for the customers near the standpipe. If a booster station could pump water out of the standpipe as the water level drops below 65 feet—adding pressure to it—it would be possible to virtually drain the tank when the Plant was unable to operate due to a power failure, providing over five days of water to the Town.

Several problems emerge, however: the stored water lasts for five days, not seven; the generator at the treatment plant might be refueled and continue operating past seven days while the standpipe is absolutely limited to five days; fire protection flows diminish with each passing hour (unless a high volume fire pump was incorporated in the booster station); and if there is no electric power at the Plant, the standpipe, less than a mile away, could easily be also affected--although installing a generator at the booster station would remedy this problem.

For technical reasons, this is not a practicable solution.

After considering the alternatives, the installation of a generator at the Plant is the most effective and reliable choice within the economic means of the Water Department.

Potential Environmental Impacts of the Project

The unwanted and foreseeable environmental impacts of the project (i.e., the harm or injury to the environment that can be reasonably anticipated as a likely result from acts or omissions taking place because of the project) occur at three separate times: one, during installation; two, during normal operational status, including maintenance and generation of electricity in response to a grid power failure, and, three, during flood conditions.

During Installation

A hole will be excavated, and gravel placed in it. Later, concrete will be delivered to the site, and a 12-inch thick slab poured. Wiring work will be done, inside, outside, overhead, and perhaps underground. Finally, a crane of some type will arrive--the Plant’s parking lot pavement comes within twenty feet of the site—picking up the generator and placing it on the slab.

While it is easy to imagine a variety of mishaps that could arise out these simple construction steps, there are no foreseeable environmental impacts of the installation. Even the mishaps are much less likely, and would be no worse in their impact, than a vehicular accident on busy Rochester Street, in front of the plant.

During Normal Operational Status

Normal operational status of the installed generator will consist of weekly running for maintenance purposes; generation in times of a grid power failure; fueling; other repairs and maintenance, and sitting doing nothing for days at a time. Because the weekly running will be powering the Plant, it need not be considered separately from emergency running.

The foreseeable environmental impacts of normal operational status are noise pollution, airborne pollution, and spilled or leaked fuel and lubricants.

  • The generator will be surrounded by a Level 2 Sound Attenuating Enclosure, with the Plant structure between it and Rochester Street, 150 feet away. It will sit 75 feet from the southeast property line, 200 feet from the northwest line, and over 200 feet from the northeast line. Contract Specifications require that the engine-generator noise not exceed 71.5 dBa at 23 feet from the enclosure. Normal generator operations will be allowed under the Town of Berwick Land Use Ordinance, Article VII, which includes noise control provisions at Section 7.6. The noise of the generator’s operation during an emergency situation is exempted in section 7.6(B), as an “emergency activity,” and the noise of the generator’s weekly scheduled running is exempted in section 7.6(A) as a “maintenance activity.”

Although the generator will add a noise source to the local floodplain, there is no foreseeable environmental impact beyond a negligiblelevel.

  • The EPA’s New Source Performance Standards have significantly reduced the permissible airborne emissions of non-road diesel engines. The engine for the generator will be required to comply with Interim Tier 4 standards when installed, and starting in 2011, the final Tier 4 standards. The same diesel fuel as used in over-the-road engines, with a 500 ppm sulfur component, will fuel the generator initially. As of June 2010, the sulfur content will be reduced to 15 ppm. It is anticipated that selective catalytic reduction, perhaps in combination with advanced exhaust gas aftertreatment, will be a significant part of meeting final Tier 4 requirements. As of 2011, the final Tier 4 regulations will apply to engines of the size that will drive the generator at the Plant, reducing the emissions standards for non-road diesel engine to the point that they approach—but are not yet as low as—road diesel standards.

Although operating the generator will add airborne pollutants, including particulate matter, nitrogen oxide, and carbon monoxide, to the local floodplain, considering the substantial reductions in emissions of off-road diesel engines, both past and soon to be; the short running times anticipated for the generator, and the busy truck-frequented Rochester Street roadway through the floodplain next to the Plant, the foreseeable environmental impact of the additional airborne emissions produced by operating the generator will be negligible.

  • The capacity of the fuel tank for the diesel engine will be at least 600 gallons, and it will be double-walled with a spill detector in the empty space between the two walls, allowing slow leaks to be monitored for, detected, and fixed before fuel escapes into the floodplain. There is no foreseeable event that would cause a sudden rupturing of the fuel tank. The CERCLA (Comprehensive Environmental Response, Compensation and Liability Act) Reportable Quantity for diesel fuel is 500 pounds, about 75 gallons. Incidental drips during filling and maintenance are foreseeable, but could be mitigated by catch pans or wiping, and wouldn’t be significant.

Although the generator will introduce a large tank of diesel fuel to the floodplain, there is no foreseeable environmental impact beyond a negligiblelevel.

During Flood Conditions

Applying the concept of foreseeability to flood conditions is particularly difficult. On the one hand, floods are known to occur on the SalmonFallsRiver and the FIRM that includes the Plant site makes straightforward probability assessments, showing a 100-year flood level and a 500-year flood level, both very unlikely occurrences. On the other hand, probability dictates that it is possible for two 500-year floods to take place in two successive years—even though the likelihood of such a flood was 0.2% in each of the years. But does that make it foreseeable to the extent that planning must take it into account?

Recent history can be helpful, yet falls into the same trap. In 2006 and 2007, there was a flood each year along the SalmonFallsRiver that by informal measurement exceeded the 100-year flood elevation of 177 feet at the Plant. But the Gambler’s Fallacy reminds us that no matter how many times the coin-toss comes up heads, there will still be no better than a 50/50 chance of tails on the succeeding toss. Statistically, there’s only a 63% chance that there will be another 100-year flood in the next 100 years.

In the final analysis, three factors ought to considered: the severity of the impact to the environment from floodwater action on the generator installation; the likelihood that flood levels that could affect the generator would arise, and the investment that would be required to prevent or mitigate the floodwater’s effect on the generator and the subsequent impact on the floodplain environment.

  • The floods of 2006 and 2007 reached about 178 feet, a foot above the listed 100-year flood elevation. Yet, had the generator been in service at that time, the flood waters would have been four feet below the lowest part of the proposed sub-base diesel fuel tank situated below the generator and engine. What’s more, from personal observation I can say that, at 178 feet, the floodwater had virtually no relative motion to the higher ground upon which the Plant is built—the surrounding water was nothing but a reservoir of stored water, pushed there by water rushing by in the floodway, but having practically no flow, no energy, itself. A repetition of those slightly-more-than 100-year flood would not produce any risk of an impact on the environment from the proposed generator.

The FIRM showing the Plant location can be used to get a rough idea of the 500-year flood level, delineated by the outer edge of Zone X. Using topographical data, it appears to be somewhere between elevation 180 and 183. If it were 180, and the flood occurred, the floodwater would reach as far as the base of the Plant’s security fence, still two vertical feet below contact with the sub-base fuel tank. At 183, however, it would be about a foot up above the bottom of the fuel tank. I imagine there would be more flow in the deeper water, also, but with only one foot of the installation to work against, the foreseeable impact on the installation, and the environment, would be negligible. The proposed generator site is not on the bank of a river, and the potential for water velocity sufficient to create destructive erosion at the base undermining the generator is very small.