By Jeff Richards
Landscape Architect


The Assabet River Rail Trail (ARRT) offers hikers, bicyclists, and other users the opportunity to experience numerous natural resources common to our region. This guide identifies the most significant natural resources along the 12.5-mile trail as it passes through Marlborough, Hudson, Stow, Maynard, and South Acton in eastern Massachusetts. It begins in Marlborough and finishes in Acton (purely for convenience sake) as if one were to walk from one end of the trail to the other.

This guide has two main objectives:

(1.) To inventory the existing natural resources along the ARRT greenway and identify key flora and fauna within the proposed pedestrian trail. More specifically, to identify habitats supporting populations of species classified as rare or endangered that could require modifying the proposed ARRT route.

(2.) To prepare a guide that can help introduce us to the diversity of nature in our "backyards."

In response to the first objective, the natural resources discussed in this guide include: surface geology and soils, water, water supplies, flood plains, wetlands, plants, animals, endangered species habitats, topographical features, vistas, and adjacent open spaces. One location along the ARRT is home to a listed species of special concern; see eastern Hudson and western Stow for estimated habitat identification. More research will need to be done to determine exactly what impact this natural treasure will have on trail alignment and design.

In Marlborough, Hudson, and Maynard the trail runs through lands that are mostly urbanized; in Stow and Acton, the trail is located in predominantly rural areas with more natural resources. From one end to the other, the ARRT follows the path of a former railroad R.O.W. - the Old Marlborough Branch, which went out of service in 1973. As an abandoned railroad bed (some segments still retaining the steel track and railroad ties), the entire ARRT rail line is a human-altered feature of our landscape.

Much of this neglected R.O.W. of the Marlborough Branch has become over-grown with a mix of native and introduced or invasive plant species. This gives the trail a 'natural" feeling, especially when experienced in conjunction with its urban or suburban surroundings.


The most signifigant natural resource along the ARRT is of course the Assabet River. The trail follows the river valley in Hudson, Stow, and Maynard, where opportunities exist to walk the trail directly along the river's edge. It is no surprise that the railroad followed the generally lazy course of the Assabet: This route offered the easiest gradient for running the rail lines. Wetland protection wasn't considered when such railroads were constructed in the 1840's and early 1850's with maximized operational efficiency in mind. Today, the earthen berms on which the railroads ran, especially where they remain in the floodplains along water bodies are particularly special land forms: They allow the public direct access to nature without disturbing sensitive environments. This provides a wonderful opportunity to reconnect with our natural surroundings.

The trail can be enjoyed as an "outdoor environmental classroom" whether one is traveling through rural or more urbanized stretches of the ARRT corridor. It is hoped that this guide will encourage further investigation by students of all ages.


downtown marlboro map Starting at the site of the former Rail Road Station off Lincoln Street in downtown Marlborough, the ARRT heads north toward Hudson Street. Located one block to the northeast is Kelleher Field, a neighborhood park with a football field, bleachers, and a children's play area.

The highest point along the ARRT is at Hudson Street, with an elevation of approximately 451.5 feet above mean sea level. This high point marks the divide between the Sudbury and Assabet watersheds. Rain falling on the ARRT south of Hudson Street flows into the Sudbury River, and rain falling on the ARRT north of this point on Hudson Street flows into the Assabet River. Most of the ARRT is within the Assabet River watershed.

Beyond Hudson Street, the trail goes through an excavated cut; exposed bedrock or ledge can be seen on both sides. This reveals the western shoulder of Okoocanganset Hill, a hilltop shaped by glaciers over 10,000 years ago.

Continuing down the hill and crossing Ash Street, Mt. Wachusetts can be glimpsed 20 miles to the northwest. This view is best enjoyed in the winter when the leaves have fallen.

Soon the trail flattens out as it traverses the top of a thirty-foot-high fill placed by the railroad to facilitate crossing a drainage swale (see * on map on Page 3.) This drainage path is one of the headwaters of Sheep Fall Brook to the west and marks the division between Okoocanganset Hill and Addition Hill. Vegetated wetlands and the buffers along Sheep Fall Brook are home to a more diverse range of plant and animal species than encountered along the trail to this point.

Thus far, we have been walking through a very urbanized area. The vegetation adjacent to neighboring backyards along the trail includes introduced or invasive species such as Norway maple, burning bush, and Japanese knotweed. The wildlife is mostly comprised of creatures that can survive in city conditions, such as gray squirrels, chickadees, and feral cats.

Addition Hill map When we enter the more natural area near Sheep Fall Brook, we observe transitional plant species, such as black raspberry, poison ivy, and gray birch. Oaks dominate the tree canopy. Red-tailed fox, woodchuck, raccoon, skunk, red squirrel, porcupine, and rabbit may be watching you from hidden spots beneath the vegetation. These woods are also home to birds such as cardinal, mourning dove, downy woodpecker, tufted titmouse, owls, purple finch, robins, and woodcock.

After passing Fairbanks Boulevard, the trail skirts along the western side of a large parcel owned by the City of Marlborough. This had formerly been the site of a landfill; now part of it is a golf driving range.

Downhill slightly from the driving range, an opportunity for a scenic lookout exists, taking in the view of Fort Meadow Reservoir to the northeast.

Hagar Hill map As we approach Fitchburg Street, the rail traverses a large fill constructed by the railroad as a stream crossing. The stream is called Flagg Brook. It carries water flowing from Sheep Fall Brook and Flagg Swamp, and runoff shed by Addition Hill. Flagg Brook in turn flows to the east into Fort Meadow Reservoir Marsh and other vegetated wetlands border Flagg Brook, and during times of heavy rainfall, flooding occurs along each bank. This is part of a wildlife corridor. From the trail, sixty feet above Flagg Brook, we are at level with tree tops. Canopy trees include red oak, white oak, red maple, black birch, white pine, white ash, and shagbark hickory. A healthy understory of small trees includes common witchhazel, speckled alder, highbush blueberry, and spicebush. This wooded corridor is the most wild and natural site the ARRT encounters in Marlborough. Beavers have been active in this area recently.

After we cross Fitchburg Street, the trail is bordered on the right by the Assabet Valley Regional Vocational High School, with athletic fields directly to the east. A wooded swamp wetlands area is situated along the trail, just north and west of the football field parking lot. To the west of the trail is Hager Hill.

Additional natural resources along the ARRT in Marlborough:

Municipal water supply Water Supply Protection District
The ARRT doesn't pass through this resource protection district; Marlborough's closest municipal water supply is Millham Reservoir in the western end of the city.

It should be noted, however, that water flowing from Flagg Brook into Fort Meadow Reservoir and then into Fort Meadow Brook do subsequently pass through public water supplies in Hudson known as the Chestnut Street WelIfield.

Rare and Endangered Species Within the Marlborough locus of the ARRT, there are no rare or endangered species listed by the Natural Heritage and Endangered Species Program maps.


We enter the town of Hudson as we begin across the Connector Road. Immediately we disappear into a world of trees along the base of a steep rocky slope to the west. This hill has no name on the USGS topographic map, although its top elevation of about 480 plus feet makes it the highest point in Hudson. To the right of the trail we see areas of shrub swamp, a favorite home for birds such as red-winged blackbird and marsh wren.

As the trail swings to the left, it passes under an old over-pass; the large, rugged stone abutments flanking the trail are significant cultural vestiges of the bygone railroad era.

To the right (or east) of the trail we soon see a wooded swamp about eight acres in size. This wetland resource is the headwaters for a small unnamed brook that flows to the northwest. The brook crosses under the trail, then parallels the trail on the left for approximately nine hundred feet before disappearing into a recent residential subdivision and subsequently joining the Assabet River. This segment of trail along the small brook is very pleasant (if we look past an array of shopping carts and other debris); it has great potential as a pocket of natural beauty. Surprisingly, just 30 feet up the steep embankment on our right are parking and loading docks of adjacent commercial enterprises, such as the Victory Supermarket.

Soon we cross Washington Street. This portion of the trail is decidedly urbanized. Species that populate this section of the trail corridor include invasive plants such as Japanese knotweed and Norway maples, and urban-tolerant animals such as gray squirrels and rats.

We have been going steadily downhill ever since crossing Hudson Street in Marlborough. The hills on each side of the trail are generally comprised of glacial till on bedrock. Between the hills are areas of sand and gravel; these were deposited and sorted according to particle size by the meltwater flowing out of the bottom of the melting glaciers. Small sand particles could be carried a greater distance by the meltwaters and typically were deposited closer to the Assabet River; larger stones couldn't be carried as far by meltwaters and often stayed higher up on hillsides.

The next significant natural landmark is the Assabet River. We traverse a high trestle that crosses the river some 40 feet below. This is the first occasion for the ARRT to cross the Assabet River. By the time we reach the Commuter Rail Station in South Acton, the ARRT will cross the river a total of five times. The river at this point is fairly fast flowing and relatively rich in oxygen due to turbulence and aeration provided by the rivers ten foot plunge over the dam 1600 feet upriver at Washington Street. The river is home to reptiles such as the snapping turtle and the northern water snake. Fish, including largemouth bass and white sucker sometimes inhabit the river at this point. Though the water quality has been improving in recent years, this stretch of river is not yet clean enough to support populations of more demanding fish such as brook trout.

Soon we come to the second Assabet River crossing, which offers a pleasant view up and down the river. It is the site of persistent river clean-up efforts by members of the community who work each spring to clear branches, logs, car tires, shopping carts, and other debris from the piers that support Main Street and the railroad bridges. With each spring flood, a new batch of entanglements are lodged among the piers, making passage difficult for canoeists and water levels higher during floods.

East of this Assabet River crossing, the trail passes homes and commercial properties. After crossing Cox Street, the municipal property for the Mulready School (formerly called the Cox Street School) can be seen to the left. Wetland areas are present both north and south of the trail. These merge with broader wooded swamplands to the east. Red maple and white pine are the dominant canopy trees.

Outflow from a pond within the Rod and Gun property to the north combines (near Wilkins Street) with a tributary draining wooded swampland from the south, and gives rise to a small unnamed stream that flows east into Stow along the trail. East of Wilkins Street the land along the ARRT becomes more wild and natural than any other trail segment in Hudson. A large portion of these lands are wetlands.

At about this point, we have entered the Zone II well-head protection area associated with the Chestnut Street municipal wellfields.

We have also entered an area listed with the Natural Heritage and Endangered Species Program as home to rare plant and/or wildlife species. This estimated habitat is roughly 75 acres in area, extending south to the former Central Massachusetts Railroad line, north to High Street in Stow, and east to the Assabet River. The exact identity of the species of special concern is not publicized in this guide in order to help protect it. Further to the east and to our right, the land rises up to become Gospel Hill.


East of the Hudson-Stow line, the trail skirts pockets of wooded swamp and marsh to the south. This area is part of a 7~acre habitat listed with the Natural Heritage and Endangered Species program, and therefore has special significance.

After crossing Marlborough Road, the trail follows Railroad Avenue to its end at the Assabet River. This is the third river crossing; actually, the railroad had two bridge spans that used a small island midway for crossing the river.

The river, its banks, and adjoining landscape in this vicinity are the most natural that we've encountered so far on our journey from Marlborough. The river valley is alive with healthy marsh, shrub swamp, wooded swamp, and a diverse range of habitat for the abundant wildlife. Amphibians, including a variety of species of frog and red-spotted newts, inhabit the river's banks. The river valley serves as an important corridor for waterfowl migration. Here, human influence is minimal and nature dominates - the reverse of what is experienced on the ARRT in Marlborough, Hudson, Maynard, and Acton.

We are also within a Water Resource Protection District. This zoning classification is aimed at protecting a potential well site roughly 1,000 feet to our north, where exceptionally high groundwater yields have been documented. This zoning district also protects the Chestnut Street wellfleld, about 1,200 feet to our south in Hudson.

The proposed trail would next pass through the back land of Honey Pot Hill Orchards. At this time, it is far from certain if the family that owns and operates the orchards will allow the ARRT to follow the old railroad bed through their property. This leaves a gap roughly nine-tenths of a mile in length before we leave Honey Pot Hill Orchards and encounter an Assabet River crossing once again. This fourth river crossing on the proposed trail occurs at a location approximately 1,200 feet upriver of Sudbury Road. The land along the ARRT continues to be fully natural, with a diverse mix of riverine and upland habitats and associated wildlife.

By the time we reach Sudbury Road, the Assabet River has grown with the addition of flows from Fort Meadow Brook and Lake Boon. The water quality has improved during its slow, meandering passage through the marshlands south of Honey Pot Hill Orchards.

After crossing Sudbury Road, the ARRT follows what is locally known as Track Road. This is a private gravel road, approximately 1-3/4 miles in length, extending between Sudbury Road and White Pond Road at the Stow-Maynard line. To our left we see the Assabet River, complete with healthy deep marsh and wooded wetland riparian buffer zones.

After walking about half a mile along Track Road we begin to see the Fort Devan Annex on our right. This property is slated to be conveyed from the Department of Defense to the U.S. Fish and Wildlife Department and become a wildlife refuge. With over 2,000 acres, the Annex is by far the largest protected open space adjacent to the ARRT. It is also the only public open space parcel next to the trail within the Town of Stow. Most of the Annex is forested, with white pine, oak, ash, red maple, black birch, and cherry making up the majority of tree species. Wetlands occur on about 20 percent of the annex and include small streams, ponds, bogs, emergent wetlands (i.e., dominated by herbaceous plants rather than shrub- or forest-dominated), and vernal pools. The Annex is home to a wide range of wildlife species and provides a rest stop to many others in migration. Annex lands continue on our right as far east as White Pond Road and a few hundred feet beyond into Maynard. These federal lands are a tremendous natural resource.

To our left, we continue to pass extensive wetlands along the Assabet River. The only turn off Track Road is a driveway to the left that leads to Crow Island. The island hosts a small, private airport and runway, which also has been a soccer field. Crow Island was mined for sand and gravel deposits, as were other sites along the river. North of the river is a large, Town-owned open-space parcel containing a Town well and the Town forest. The combination of these pristine, wooded lands, the river, and the Annex to our south makes this the most wild and natural place along the ARRT.

Elizabeth Brook joins the Assabet River close to the Stow-Maynard line. Labeled as Assabet Brook on the USGS topo-map, it drains most of central Stow and is the largest tributary to the Assabet River.

Representative species present along the ARRT:



  • Red, White, and Silver Maples
  • Sugar Maple
  • Black and white Willow
  • River and Gray Birch
  • Hemlock
  • Swamp White Oak
  • Red and White Oaks
  • Pignut and Shagbark Hickory
  • White Cedar
  • White Pine
  • Quaking Aspen
  • White Ash
  • American Beech
  • Black Cherry
  • Buttonbush
  • Elderberry
  • Highbush Blueberry
  • Arrowood
  • Sweet Pepperbush
  • Meadowsweet
  • Swamp Azalea
  • European Buckthorn
  • Winterberry Holly
  • Speckled Alder
  • Silky and Gray Dogwood
  • Black Chokeberry
  • Yellow Flag
  • Blue Flag
  • Jewelweed
  • Purple Loosestrife
  • Cardinal Flower
  • Pickerel weed
  • Arrowhead
  • Arrow Arrum
  • Joe-Pye Weed


  • Common Cattail
  • Tussock and other Sedges
  • Great Bulrush
  • Soft Rush
  • Wild Rice
  • Reed Canarygrass
  • Royal and Cinnamon Ferns
  • Marsh and Sensitive Ferns

Birds along wooded riverbanks

  • Belted Kingfisher
  • Common Flicker
  • Downey Woodpecker
  • Yellow Warble
  • white-breasted Nuthatch
  • Tufted Titmouse
  • Black capped Chickadee
  • Wood Thrush
  • Gray Catbird
  • Cedar Waxwing
  • Northern Oriole
  • Common YelIowthroat
  • Tree Swallow
  • Common Grackle
Birds near fields or marshes
  • Bobolink
  • American Woodcock
  • Song Sparrow
  • KilIdeer
  • Barn Swallow
  • Cuckoo
  • Flycatcher
  • Wren
  • Indigo Bunting
  • Catbird
Birds near marshes
  • Great Blue Heron
  • Green-backed Heron
  • Red-winged Blackbird
  • Marsh Wren
  • American Bitten
  • Egret
  • Rail
  • Bittern
  • Coot
  • Gallinule
  • Wood Duck
  • Black Duck
  • Mallard
  • Ring-necked Duck
  • Canada Geese
  • Gadwall
  • Shoveller
  • Green-winged Teal
  • Sphagnum Moss
  • Blue-joint Grass
  • Yellow Pond Lily
  • White Water Lily
  • Pickerel Weed
  • Watershield
  • Duckwceed
  • Water Clover
Feathery Submerged Plants
  • Low Watermilfoil
  • Common Elodea
Ribbon-leaved Plants
  • Water Celery
Upland Meadow Plants
  • Sweet Fern
  • Sedges
  • Lowbush Blueberry
  • Beaked Hazelnut
  • Hayscented Fern
  • Canada Lily
  • Lady Slippers
  • Grasses
  • Forbes
Reptiles and Amphibians
  • Hognose Snake
  • Eastern Box Turtle
  • Snapping Turtle
  • Painted Turtle
  • Spotted Turtle (on special concern list)
  • Eastern Garter Snake
  • Northern Water Snake
  • Bullfrog
  • Toads
  • Green Frog
  • Wood Frog
  • Tree Frog
  • Red-backed Salamanders
  • Spotted Salarnanders
  • Red-spotted Newt
  • Leopard Frog
  • Pickerel Frog
  • Crayfish
Birds of Prey
  • Bald Eagle
  • Screech Owl
  • Barred Owl
  • Great Homed Owl
  • Largemouth Bass
  • Black Crappie (Calico Bass)
  • Brook Trout (stocked in tributaries)
  • Pickerel
  • Bluegill
  • Brown Bullhead
  • Red and Gray Fox
  • Little Brown Bat
  • Beaver
  • Muskrat
  • Raccoon
  • Skunk
  • Mink
  • River Otter
  • White-tailed Deer
  • Little Brown Bat
  • Mice, Shrew, Rats, Voles
  • Chipmunk, Moles
  • Porcupine
  • Coyote
  • Moose
  • Red and Gray Squirrels
  • Woodchuck
  • Opossum
  • Long-tailed Weasel
  • Eastern Cottontail
  • Dragonflies
  • Green Darner
  • Twelve Spot Skimmer
  • Blackwinged damselfly
  • Common Forktail
  • Bluet
  • Sympetrum
Aquatic Inseet Nymphs
  • Dragonfly Nymphs
  • Damselfly Nymphs
Other Aquatic Insects:
  • Whirligig Beetles
  • Water Boatmen
  • Water Striders


As we cross White Pond Road, we enter Maynard. Tuttle Hill and the forested lands of the Fort Devens Annex are to the south; a few houses sit between us and the Assabet River to the north. The next two thousand feet of trail is the most natural and picturesque in ARRT's passage through the Town of Maynard. Though privately owned, some maps refer to this stretch as Riverside Park."

Once past the houses, the river flood plain is populated by a red maple wetland. A number of small drainage swales direct runoff under the trail into this resource. A portion of this red maple wetlands is protected land owned by the Massachusetts Department of Environmental Management.

Taylor Brook and Thanksgiving Pond to our right offer some of the most scenic vistas along the ARRT. Extensive marsh, open water, and minimally developed land adjacent to the Devens Annex Wildlife Refuge provide a rich mix of habitats.

The Maynard Department of Public Works is located on our right after we pass Thanksgiving Pond.

The next significant natural resource is the Assabet River, which we cross in downtown Maynard at Riverfront Park behind the Post Office. This point marks the lowest elevation along the ARRT of roughly 170 feet above mean sea level.

As we head north out of downtown Maynard, it is not until after we've crossed Acton Street that we begin to observe vestiges of a more natural world. This takes the form of a vast wetlands plain to the west of the ARRT, which spans the Maynard-Acton line.

Though Maynard is perhaps the most densely urbanized of the five ARRT communities, ironically, it has the greatest number of publicly owned open-space parcels along the trail corridor. While generally too small to provide much habitat value for wildlife, each small green space along the ARRT in Maynard contributes important breathing room for the Town's human inhabitants.


The southernmost portion of the ARRT in Acton is flanked on each side by Red Maple Swamp. These wooded wetlands give rise to a brook that flows under the trail, under Rte. 27, and eventually joins Pratt's Brook. We are within a Groundwater Protection District Zone 3, which means that Acton's zoning bylaws set some limitations on land use activities that would be detrimental to groundwater purity. This red-maple swamp is also within the 100-year flood plain.

As we proceed north on the trail, first passing commercial properties, then passing homes on the right, the trail rises gently out of the flood plain and wetlands and becomes surrounded by second-growth forest. Trees include red and white oaks, white pine, black birch, hemlock, red maple, white ash, and northern red cedar.

Soon we see a hay field to our left. This is a special attribute for the proposed trail. It and other agricultural lands to the west of Fort Pond Brook Mill Pond are the only actively farmed land along the ARRT. Fields and their wooded edges are important for wildlife such as rabbits, moles, mice, woodchuck, pheasant, and a variety of songbirds.

In the vicinity of Sylvia Street we pass through a cut created by the railroad to ease the grade. The soils of the Stonefield Farm to our west are classified as 'Prime Farmland" and State or locally important farmland." These good soils vary with poorly draining areas of glacial till that were deposited by the glacier's retreat 10,000 years ago. Till is a compact mixture of sediment composed of a wide range of grain size - from very fine clay particles to large granite boulders - that were compressed by the glacier.

Soon the trail is once again flanked by wetlands. These provide the natural transition to Mill Pond, which was created by damming Fort Pond Brook. The Mill Pond and its surroundings are strikingly beautiful. A trestle crosses the pond, offering a pleasant resting point. Fish such as largemouth bass and perch reside in the pond, and waterfowl including great blue heron, wood duck, osprey, and mallards are occasionally observed. Beaver activity has been reported in the Fort Pond Brook drainage basin. The brook that enters Mill Pond to our West is an important wildlife corridor. The Town's Open Space Action Plan proposes the establishment of a greenbelt along Fort Pond Brook. White-tailed deer and eastern coyote travel along these types of corridors. The area around the Mill Pond, with its wetlands and floodplain, is part of the Groundwater Protection District Zone 3. Fort Pond Brook ultimately provides water that goes into the aquifer that supplies the Lawsbrook well field a few miles to our east.

The trail continues north, along the edge of Mill Pond. Were we to continue around the pond and hook back (south, hugging the embankment of Main Street), we would arrive at the half-acre, Town-owned park called Mill Pond Recreation Area. This parcel is the only Town-owned land adjacent to the ARRT in Acton. It is near the 1898 stone dam that impounds the Mill Pond.

Though the Assabet River Rail Trail terminates at the MBTA commuter rail a few blocks to our north, the land that provides our connection to that terminus is fully urbanized. The Mill Pond Recreation Area marks the end point of significant natural resources to be encountered along the ARRT.


The following sources were drawn upon to prepare this guide. They are great resources for additional information about the natural treasures along the Assabet River Rail Trail:

Beals and Thomas, Inc. "Maynard Open Space and Recreation Plan," Maynard Conservation Commission and Maynard Open Space and Recreation Plan Steering Committee, 1997.

DeGraaf, Richard M. and Deborah D. Rudis. "New England Wildlife: Habitat, Natural History, and Distribution," U.S. Dept. of Agriculture, Forest Service, Northeastern Forest Experimental Station, General Technical Report NE-108, 1983.

Ghiloni, Linda, et. al. "Town of Hudson Open Space and Recreation Plan," Hudson Recreation Dept., 1997.

Laparee, Jonathan M. "How Greenways Work, A Handbook on Ecology," lpswich, MA: National Park Service and the Atlantic Center for the Environment, 1992.

Lewis, Cathy Buckley. "Assabet River Rail Trail Feasibility Study," Boston: Central Transportation Planning Staff, 1997.

Madow, Ron. "The Concord, Sudbury and Assabet Rivers," Marlborough, MA: Bliss Publishing Company, Inc., 1990.

Ryder, Priscilla, et. al. "Marlborough Open Space and Recreation Plan," Marlborough Conservation Commission, 1998.

Tidman, Tom and Andrea MacKenzie, et. al. "Town of Acton Open Space and Recreation Plan: I 9~2001. Acton Conservation Commission, 1996.

U.S. Fish and Wildlife Service. "Study and Evaluation of Wetlands and Wildlife Habitat in the Fort Deven-Sudbury Annex, Massachusetts," 1993.

Weathers, Pam, Dwight Siper, Malcolm FitzPatrick, et. al. "Town of Stow Open Space and Recreation Plan. Stow, MA: Open Space Working Committee, 1997.


Illustrations of amphibians and reptiles by Abigail Rorer, illustrations of birds by Charles Joslin, and illustrations of mammals by Roslyn A. Alexander, D.V.M., BSc., are reprinted from "New England Wildlife: Habitat, Natural History and Distribution" by Richard M. DeGreaf and Deborah D. Rudis, General Technical Report NE-I 08.1983.