|Location||Middlesex County, Massachusetts|
LAKE COCHITUATE Latitude and Longitude:
|Catchment area||17 sq mi (44 km2)|
|Basin countries||United States|
|Max. length||3.76 mi (6.05 km)|
|Surface area||625 acres (2.53 km2)|
|Surface elevation||154 ft (47 m)|
|Settlements||Natick, Wayland, Framingham|
Lake Cochituate is a body of water in Natick, Wayland, and Framingham, Massachusetts, United States. Originally a reservoir serving Boston, it no longer serves that function, and is now a local recreational resource and home to Cochituate State Park.
Lake Cochituate consists of three linked ponds known as North Pond, Middle Pond, and South Pond. A large peninsula in South Pond is the site of the US Army Soldier Systems Center, and the eastern shore holds the trails of Pegan Cove Park. Middle Pond is home to Cochituate State Park, which includes boat ramps and a picnic area. North Pond is the site of both Wayland Town Beach and Saxonville Beach of Framingham.
On the edge of Middle Pond is the new MathWorks Lakeside campus . This building was originally a Carling brewery, built in 1957. The former Saxonville Industrial Track runs alongside sections of the lake, which brought supplies to both the Carling Brewery, the ITT Continental Bakery, and a Green Stamps warehouse located on the edge of the lake in an area formerly called an industrial park. The Cochituate Rail Trail will run along the lake on the former track's right-of-way, from downtown Natick to Saxonville, a section of Framingham.
The three ponds and their connector ponds cover a total of 625 acres (2.53 km2). South of Cochituate, the 40-acre (160,000 m2) Dug Pond is the site of Natick High School. The Lake Cochituate watershed, part of the Sudbury River watershed, encompasses 17 square miles (44 km2) in Natick, Wayland, Framingham, Ashland, and Sherborn. This in turn is part of the Concord River and Merrimack River watersheds. Cochituate is also the name of a village in Wayland.
In 2005, a severe thunderstorm occurred that produced a violent microburst that knocked down dozens of trees and injured some visitors, according to the Massachusetts Department of Conservation and Recreation. Two teens, Ahmie Harman and Valeria Barbier, had a tree fall on them, while another teen, Oliver Barbier, was caught in the lightning storm. Though sustaining injuries, all soon recovered. A memorial plaque, in witness of the event, has been placed there to remember them and others who survived the storm. 
Lake Cochituate was created by the construction of Lake Cochituate Dam to provide a reservoir for water supply to the city of Boston, via the 14-mile (23 km) Cochituate Aqueduct. Lake Cochituate was the first major water supply system built for the city, and replaced the previous usage of Jamaica Pond. Developed from 1848 to 1863,  it supplied Boston's water until 1951, by which time it had been supplanted by the larger Wachusett and Quabbin Reservoir supplies. The surveys and plans for the project were performed by civil engineer James Fowle Baldwin (1782–1862), the son of Loammi Baldwin who designed the Middlesex Canal, and younger brother of Loammi Baldwin, Jr. (1780–1838) who authored the earlier studies for a Boston water supply. Its 1890 dam, replacing two older dams on the lake's northwestern outlet, is listed on the National Register of Historic Places. The former gatehouse for the Cochituate Aqueduct is located on the east side of the lake.
The following is taken from the local "Natick Superfund" website regarding the toxins currently found in Lake Cochituate.
A solvent-contamination plume is in the groundwater below Building 36. Monitoring well testing found chlorinated solvents leaking from underground into two portions of the Lake Cochituate shoreline. Sensitive tests have detected these solvents in lake waters and sediments.
Polychlorinated biphenyls (PCBs) in Lake Cochituate and Pegan Cove: PCBs have been found at the Natick labs in soils and in lake sediments near Kansas Street and the T-25 outfall, likely caused in part by a PCB transformer explosion in 1984.
Ecological toxicity testing found that lake sediments were toxic to aquatic life. Oxygen-poor conditions in the sediments were also factor. Bluegill, bass, and eels all show PCB contamination near the Army Labs, at levels up to and greater than 5,000 parts per billion. Animals (including people) eating these fish would ingest enough PCBs to be harmed. A review of Massachusetts Fish and Wildlife data showed that Lake Cochituate fish have PCB levels up to 180 times higher than the statewide average.
A warning against eating bass and eels is in effect for Lake Cochituate due to PCB contamination. Fish from Natick's Lake Cochituate should not be eaten due to the proven PCB contamination. No PCB cleanup is planned because the Army assumes that no one is eating more than 1/3 of an ounce of de-skinned lake fish fillet per day. Those who eat more fish, or any amount of eels, or unskinned fish will receive higher exposures to PCBs. The Army determined that Natick's animal populations were large enough to absorb the deaths of the animals which forage around the Natick Labs.
The Army added three new monitoring wells to the area between the Labs and the Town of Natick drinking water wells beside Route 9 (Worcester Road) near MathWorks Lakeside campus. These wells will improve the odds of detecting chemicals as they are drawn into the Town's water supply wells.
- Leonard B. Dworsky, Division of Water Supply and Pollution Control, United States Public Health Service, 167 pp., 1962.
- "Lake Cochituate Resource Portal". Retrieved April 12, 2010.
- "Cochituate State Park". Retrieved November 24, 2007.
- "Cochituate Rail Trail". Retrieved April 28, 2017.
- Report on Introducing Pure Water Into the City of Boston. By Loammi Baldwin, Jr., published 1834, 78 pages.
- Report on Introducing Pure Water Into the City of Boston. By Loammi Baldwin, Jr., published 1835, 143 pages.