Nantucket's water world
BY PETER B. BRACE INDEPENDENT WRITER
H eavy rains during the later part of July may have staved off an outdoor watering ban, yet the island's annual peak usage period — the weeks before and after the Boston Pops are upon us.

PHOTO BY ROB BENCHLEY Water company general manager Bob Gardner in the pump house at the state forest well.

Wannacomet Water Company broke its monthly pumping record of 77 million gallons set in June 2007 with 79 million gallons pumped this June.

Records for July and August are likely to be broken as well, despite the water conservation measure taken this season of alternating watering days of the week for odd and even-numbered island properties.

While there are copious amounts of water deep down in the island's sole source aquifer, the ability of the town's system of pumping and storage to meet all water needs, especially for firefighting, is in jeopardy during periods of drought and heavy pumping loads.

"It's all sitting there," said Bob Gardner, manager of the town owned Wannacomet Water Company. "There's no river flowing, connecting to the mainland's water supply. What we have is what we have. There's a sole-source aquifer, but all that means is that there is one way of recharge."

Circular chart recorder keeps track of the numbers of gallons per minute pumped out of the ground during a 24 hour period. In this case, it is pumping 888 gallons per minute.

Precipitation — rain, sleet, snow, hail and fog — is that source, but this does not mean that the island lives and dies by what falls from the skies.

Gardner estimates Nantucket's aquifer at trillions and trillions of gallons of icy cool water resting beneath the island's sandy landmass in various layers separated by clays and rock, and acknowledged that the water pumped from the ground hardly puts a dimple in our water supply.

It is not the amount of water below ground that makes Gardner anxious, but the rate at which the water can be sucked out, the amount that can be stored on the surface, how quickly it is used and the concentration of contaminants.

These factors force restrictions of its use even though at the water company's most heavily relied on well in the State Forest, there is more than enough water coming out of the ground.

PHOTO BY ROB BENCHLEY Rob West, water company employee, in the Wyers Valley pump house making sure the operation is running smoothly.

"The most amazing thing about the water aquifer at this location is pumping at 900 gallons per minute, 1,296,000 gallons a day and you do that for 10 months and then turn the pump off, within 20 seconds, the water level is back to its original level," said Gardner. "That is some recovery. I'll bet that there isn't another well in the Commonwealth that does that."

Still, Nantucket's physical plant, which does all that pumping, Wannacomet's three wells and two in 'Sconset, can only handle so much.

H2-slow

Why would Gardner even consider putting the kibosh on nightly automatic watering schedules if there is so much water deep down inside our aquifer?

Because of days like July 2 when automatic commercial and residential irrigation systems switch on — 2 a.m. to 5 a.m. — when a peak rate of 24,600 gallons per minute drained out of the Washing Pond Road tank at an average of 4,300 gallons per minute with total water demand for these record three hours at 592,000 gallons.

An emergency repair being done by Aetna Pump Company water specialists in 2006 at 'Sconset gravel-packed well.

The tank at Washing Pond Road stands 117 feet tall and holds two million gallons, but only 777,000 of that is usable at the state-required minimum pressure of 20 pounds per square inch. That water is between 60 and 102 feet in the tank and stays above 60 feet with the town's pumps pumping 2,600 gallons per minute into the tank.

'Sconset's tank is 85 feet tall and holds 192,000 gallons, 57,000 gallons of which is usable for water pressure. From its new, gravel-packed well, 'Sconset's water system pumps around 750 gallons per minute into its tank off New Street.

While both water distribution systems do not have the smarts to choose between some giant lawn on the harbor getting watered before daybreak or firefighters dousing a blaze in the Old Historic District, Gardner's primary goal is the latter.

To meet people's water needs and keep up a good head of pressure, the town's water tower has to provide around 3,000 gallons per minute for three hours downtown for firefighting needs. For 'Sconset, 750 gallons per minute for one hour is required.

Irrigation systems for home and commercial use tax the island's stored water supply.

"The key is the sustainability," said Gardner. "They [the fire trucks] provide the pressure with their pump, but how much water do we have to give them for a long time? By law, you have to maintain 20 PSI at your highest location and it is recommended that you maintain 35 PSI."

Water, water everywhere

In 1878, before the town put up a water tower overlooking Washing Pond and sunk wells at Wyers Valley south of Milestone Road, Moses Joy, Jr. built a steam- and later a gasoline-powered pumping station on Washing Pond, according to Gardner.

The pumping station operated until 1929, when Joy sold his operation to American Waterworks, which in turn, sold its operation to the town in 1987.

Nantucket's water comes from four wells no deeper than 180 feet; one in the State Forest off Lover's Lane, two in Wyers Valley and one in 'Sconset. The wells pull water from a soup of sandy soils in the top layers of the aquifer.

PHOTOS BY ROB BENCHLEY Water collection main at the Wyers Valley pump house.

"If you go deep enough, it's big, beautiful, cold and fresh with no bacteria," said Dr. Sarah Oktay, director of the UMass Boston Nantucket Field Station. "If it's somewhere shallow and septic systems are getting into it, you couldn't filter it enough."

In an effort to comprehend the shape, depth and overall make-up of the aquifer and the potential for saltwater intrusion, the town hired Dr. Mark Person of the University of Minnesota's Computational Laboratory in the Department of Geology & Geophysics in 2001 to do a model of the aquifer.

Dr. Person's model showed that the aquifer is closest to the island's surface at its shores and deepest in its interior and that various layers of clays may segment the aquifer into layers of clay and water all resting on volcanic rock. According to the U.S. Geological Survey, which last produced a map of Nantucket in 1979, it found fresh water at 528 feet, while drilling a test well down to 1,600 feet off Russell's Way in 1975. At the bottom of this test well, said Dr. Person, 495 feet below sea level at 1,600 feet, the U.S.G.S found Triassic basalt, volcanic rock created late during the Mesozoic Era around 248 million years ago.

Proposed water storage tanks for 'Sconset and Wannacomet. The projects are currently out to bid.

From this study came a threedimensional picture of the island's aquifer its upward and outward pressure keeping saltwater intrusion down to a minimum.

"The conclusion is we have very little to worry about from saltwater intrusion coming up, maybe laterally, because we don't pump really heavy year-round and it sort of comes back to where it was," said Gardner.

Where ground water is closest to the surface along the shore such as in Madaket, where it is as close as 12 feet, sodium levels can be abnormally high in residents' private wells. Walk in the water along Monomoy at low tide and you can feel the cooler fresh water seeping out as pressure on the aquifer's perimeter relaxes.

PHOTOS ROB BENCHLEY The Washing Pond water tank off Cliff Road holds 2 million gallons of water.

"The balance in the aquifer is maintained by the tide and the pressure," said Gardner. "As the tide goes out, the hydrostatic pressure goes off and when the tide comes in it pushes it back up. If it didn't, you'd have artesian conditions, the water would bust through the surface on Nantucket."

There are several places on the island where this does happen in the form of springs including Eat Fire Springs marked with a plaque at 19 Wauwinet Road and in Folger's Marsh on the south side of Polpis Road.

With the aquifer so close to the surface of the island, saltwater intrusion is not the only contaminant the town worries about. Because of toxic runoff from impervious surfaces such as roads, leaching of fertilizers into the ground, petroleum drippings from vehicles in junkyards and an ocean of other potential contaminants, in 1997, Town Meeting voters adopted standards of use for Wannacomet's 4,600-acre wellhead protection district to protect the island's water supply.

"Some of the shallow wells that I'm measuring are deeply impacted, some of the ground water is so contaminated you could actually pump it onto your lawn and fertilize it because there's so much phosphate in it," said Oktay who monitors 18 water quality test wells around the island. "Where we're getting our town drinking water or water from any other well that is approximately 100 feet deep is very well protected because of a combination of clay layers and a large amount of filtration medias."

Pumping and storing

Starting at around 4 p.m. on any given beach day during the summer, water use spikes as people return from the beaches or other outdoor activities, and jump into the shower to wash off sand, dirt and sweat.

This enormous collective clockwise turning of faucets pulls water from the island's two water storage tanks, which flows from the tank through the town or 'Sconset water districts' mains to water service connections and into homes and businesses within either district. Additionally, automatic lawn and garden irrigation systems kicking on for the three hour early morning period strain these two water systems further.

Water from the town distribution system originates from the well in the State Forest off Lover's Lane, a well in Wyers Valley and the original Wannacomet 1914 well. 'Sconset's water comes from wells near the ball fields off the east end of Milestone Road. These wells consist of pipes running down into the sandy, watery top layers of the aquifer. The bottom 20 feet of the pipes are packed with filters and equipped with impellers that move the water up out of the wells. The open ends of the pipes sit on columns of gravel packed down into the top of the aquifer.

When the pumps are on, the impellers turn, moving water from the aquifer, through the gravel, through the filters and up through well piping and out through water mains to the storage tank on Washing Pond Road.

Gardner said that Wannacomet relies on the State Forest the most and that Memorial Day through Labor Day, most of the town's water comes from a well drilled in 1914 consisting of 70, 2.5-inch pipes sunk 48 feet into the ground

The sole source description of our aquifer may sound like a tenuous dependency on what falls from the sky, but consider this: in the 4,600- acre wellhead district protection area, four billion gallons of water percolates down to the aquifer annually and Wannacomet pumps 600 million gallons a year, said Gardner.

And by 2010, the town's water system will have a second, new twomillion gallon storage tank off Polpis Road opposite Shimmo Pond Road and 'Sconset, a 400,000-gallon tank behind its existing well field. Both will be elevated storage tanks, meaning that their entire contents will be stored high enough so as to be completely available for water pressure. I