Septic tank
While a properly maintained and located septic tank does not pose any more environmental problems than centralized municipal sewage treatment, certain problems can arise with septic tanks in unsuitable locations. Since septic systems require large drainfields, they are not suitable for densely built areas.
Sudbury Aqueduct
The aqueduct consists primarily of a horseshoe-shaped brick lining that is in diameter and high. The bricks are set in concrete atop a foundation of concrete and stone rubble. The aqueduct is covered by an arch built of brick. The aqueduct was initially designed to carry 80 million gallons of water per day, limited by the Rosemary Brook Siphon. An additional barrel was later added to the Rosemary Brook Siphon increasing the design capacity to 110 mgd. The main conduit from Farm Pond to Chestnut Hill Reservoir is inclined one foot per mile. At a number of places on the aqueduct small buildings were built to house control equipment of various sorts. These include a gate house at Farm Pond (abandoned after a channel was constructed feeding the aqueduct from Framingham Reservoirs #1-3 due to poor water quality at Farm Pond), a metering house in southeastern Framingham, and control houses over weirs where the aqueduct crosses over other bodies of water. These control points allow water from the aqueduct to be diverted into the watersheds it crosses. There are also control houses on either end of the Rosemary Brook siphon in Wellesley, where the water is sent through cast iron pipes to traverse an extended low spot on the route. This stretch of the aqueduct illustrates a number of the techniques used in its construction: parts of the aqueduct here are raised on an embankment, while others are in a cut, due to significant changes in local topography. Portions of the aqueduct in Natick and Newton were created by tunneling, the longest being a tunnel in Newton. In addition to the Echo Bridge, the aqueduct also passes over the "Waban Arches" bridge. Located in Wellesley near the Elm Bank Reservation, this nine-arch bridge carries the aqueduct across a valley containing Waban Brook near its mouth at the Charles River. The aqueduct formally ends at a terminal house just above the Chestnut Hill Reservoir in Newton.