Mont Vernon has no public water or sewage utilities; every house in town currently manages its own water supply and waste disposal, as is typical in rural communities. Groundwater supplies virtually all the domestic water in this country.

Groundwater is a renewable resource, but not an infinite one and it is not found equally everywhere. Mont Vernon, being sited on a rocky hilltop, is not blessed with generous amounts of groundwater uniformly available. Water is a finite resource in town, and it must be managed carefully to ensure that it is not withdrawn faster than it can be replenished or that it is not contaminated due to waste disposal.

This chapter provides a summary on the water and septic situation in Mont Vernon, as well as a few recommendations for actions the town might take relative to water. The final pages of this section contain background information, essentially a primer, on water sources, the mechanics of public water suppliers, and the mechanics of septic disposal.

Water in Mont Vernon

The USGS Water Investigation Report 86-4358 states "Mont Vernon does not seem to have any stratified-drift aquifers that could be developed into a municipal water supply. Individual users in Mont Vernon rely mostly on water in the till or bedrock aquifer for household needs."

In essence, we have water, but no one source that could serve a significant number of households. The town’s population today relies on private wells and must assume it will continue to do so in the future.

Clean water is essential for human health. Mont Vernon residents rely on groundwater for drinking and cooking. We must be extremely careful to protect the cleanliness of our groundwater, as it is a key component of the health of the community.

Water is a resource that is renewed locally, but recharge is slow because the water must seep through a layer of rock. The nature of bedrock groundwater is that the size and direction of fractures within the rock dictates the amount and yield of water. One well may have sufficient water yield, but the next well taps different fractures and may have a much lower yield. All local wells tap into the same reservoir of groundwater, but the high yielding well is in the more porous rock. Water flows towards more porous rock; therefore it flows away from low yielding wells toward the high yielding wells. The number of wells in an area also affects water supply because each well draws the water table lower in its immediate vicinity. The more wells, and the closer they are together, the lower the local water table becomes.

A public water supply is not an option for any significant portion of the town either now or in the future. There is no aquifer in town from which to get water. The cost of running water mains any distance is enormous. Public water is not economically feasible in Mont Vernon. Individual homeowners must continue to be responsible for their own water. Mont Vernon as a town must remain aware of, and protective of, its water resources, as they are fragile and critical to residents' health. The American Ground Water Trust has well documented the connection between water quality and human health in publications such as Ground Water, A Source of Wonder: Drinking Water From Wells (1999).

Sewage Disposal

In cities, most houses are hooked to a municipal sewer system. A city-operated sewage treatment plant cleans everything from the sewer system and then pours it back into the ground. Houses not on a municipal sewer system usually pour waste into a septic system. Solid waste stays in a septic tank; the liquid flows out into a leach field where it seeps slowly into the groundwater.

Mont Vernon has no municipal sewer, nor do we ever expect to have one. Everyone pours waste into some sort of waste system. All waste systems eventually return the liquid waste to the groundwater. Some septic systems clean the waste better than others. The only given is that the waste will eventually and inevitably return to the groundwater and we will drink it.

Properly designed, constructed, and maintained septic systems filter wastewater sufficiently well so that when it has returned to the ground via a leach field, filtered back into the groundwater and migrated to a well, it is clean enough to drink.

Improperly designed, constructed, or maintained septic systems return polluted water to the groundwater. Wells constructed too close to even a good septic field will pull up the returning wastewater too soon for it to have been adequately cleaned.

A Municipal water treatment plant is not an option at any time in the future. Generally, our options are few: we need clean groundwater, and we must continue to rely on private waste treatment systems - septic systems. We must build and maintain these systems while understanding that they eventually feed our drinking water, and therefore we must do our utmost to see they are well designed and located sufficiently distant from groundwater sources so the waste is properly filtered before it rejoins the town’s source of drinking water. In the end it remains the individual homeowner’s responsibility to manage each home’s waste responsibly.

Recommendations

• The town should institute a program to monitor the change in static water level in wells over time in the areas of high density growth. Recently drilled wells were registered with the state, and their original static water level was recorded. Noting the change in the static well level might provide us with an indicator of stress being placed on the amount of groundwater available.

• The town's water is safe only if septic systems are well-constructed and maintained. Education is one way to help homeowners realize the importance of maintaining their water and septic systems. Although the state ultimately governs septic systems, the town building inspector is responsible for reporting non-compliance. Town regulators and inspectors should be particularly vigilant and wary of potential groundwater problems when considering acceptance of septic construction in order to protect groundwater quality.

Nevertheless, water and waste remain the responsibility of the individual homeowners.

Information About Water

Infiltration is the process of water moving down through the soil.

Recharge refers to the amount of time it takes for infiltrating water to reach the water table.

Porosity is the measure of how many holes there are in the ground/rock that can hold water.

Permeability is the measure of how easily water can flow through the holes.

(Example of the difference between Porosity and Permeability. Clay is very porous so it can hold significant amounts of water. Clay is not at all permeable, meaning water cannot move through clay at all.)

Aquifer is a general term for saturated deposits that are both porous enough and permeable enough to provide water in high volumes.

Confined aquifer – bounded top and bottom by impermeable layers.

Artesian aquifer – an aquifer that is under pressure so when it is penetrated, water is pushed out.

Perched aquifer – a small porous permeable area bounded by impermeable layers. Generally unpredictable and results in wells of varied depth and yield.

Stratified Drift Aquifer – stratified drift refers to layering of sediments. They are usually deposits of a stream running off a glacier in the Ice Age. The sediments are laid down in layers of similar particle size based on the flow of the stream. (Fast flowing streams lay down big rocks. Slow streams lay down little rocks.) As the glaciers receded the stream deposits naturally became stratified. These deposits are generally both porous and permeable so when they are saturated (below the water table) they are good sources of significant volumes of water.)

Till Aquifers - till is rock and soil left by the glaciers melting out from under them. They were not part of the run-off. Till is easily likened to the dirt on snow banks left when the snow bank melts. Because the soil types are so random, generally till aquifers are very porous but not very permeable. They hold water, but water does not move readily through the soil, and therefor it does not lend itself to providing significant amounts of water.

Draw-down – the effect on the water table by withdrawing water.

Cone of depression – Every well draws the water table down in the immediate area of the well. How big this "cone of depression" is depends on the how permeable the soils around the well are and how fast water can flow back into the area around the well after water is withdrawn.

Yield is the measure of water flowing into a well bore. It is usually measured in gallons of flow per minute.

Static Water Level is the level of water in the well bore when there is no, and has been no, demand. Generally it is the level of the local groundwater table. Occasionally it is higher than the water table if the aquifer that the well penetrates is under pressure.

Recharge Area – the surface area from which all water seeps down to enter, or recharge, the water table. The recharge area for large aquifers can be roughly related to the watersheds that flow into the aquifer area. On a small, domestic well, the recharge area is more difficult to define as private wells rely on the local direction of groundwater seepage. Certainly areas within several hundred feet of a well directly affects recharge, but because of the rate of groundwater flow (often measured in inches per day) true recharge areas affecting specific wells are more depend on internal rock fracture orientation. The result is a well’s primary recharge area may be physically downhill from the well.

Water moves naturally through the ground to discharge points. The water is removed from the ground and distributed, eventually returning to the ground to begin the cycle again. The returning of the water to the ground is the recharge part of the water cycle.

Water is removed from the ground, used, and returned to the ground, but not always in the same place from which it was removed. Plants take water from the ground and put it in the air and it leaves the area. Domestic wells pull up groundwater for use by people. Domestic septic systems return most domestic water to the ground and recharge the groundwater system.

Generally groundwater supplies in New England are naturally recharged during spring and fall. Rainwater during the growing season generally does not come in significant quantities to have significant amounts go past the root zone. Rainwater must come in the spring and fall when trees/plants use less water for it to be a source of groundwater recharge. Winter rain is lost because water runs off the frozen ground. Snow that melts in the spring and soaks into the thawing ground is a significant source of recharge water. Snow melting in midwinter when the ground is frozen is generally lost to groundwater recharge.

The part of the water cycle the homeowner can control is irrigation. Watering lawns and gardens is a net loss to the local groundwater supply. Plants normally trap all the water in their roots preventing the water from seeping down to the groundwater level. Septic fields leach below the root zone, so household water is largely returned to groundwater.

The natural evidence of the seasonal movement of the groundwater levels are streams. Streams are groundwater discharge points. Ground water levels are naturally recharged in the spring by rains and snow melts, which cause the water table to rise, and the streams to rise. In the summer the water table falls, recharge slows or stops, and stream flow lessens or stops. During the late autumn rains, the groundwater recharges and streams begin to flow again.

Before drilling equipment became common and cost effective to operate, wells were large shafts dug in the ground, lined with stone. The wells were usually dug as deep as possible, and digging stopped when either bedrock was reached or incoming water filled the hole. These dug wells were and are subject to contamination and are generally no longer constructed.

Drilling equipment makes it possible for wells to be drilled in bedrock, tapping deeper groundwater sources. A shaft generally about 1.5 feet in diameter is drilled in the ground. The top of the shaft runs through soil and unconsolidated rock and is lined with an impermeable steel casing. After the well shaft gets into the top layer of bedrock, the well bore is an unlined hole into which groundwater can seep through the natural fractures in the rock. The quantity of water a well supplies is a function of the water table, the nature of the rock surrounding the well bore, and the depth of the well.

Drilled wells are commonly and usually mistakenly called Artesian Wells. A drilled well is a shaft drilled below the water table. A drilled well becomes an Artesian well if the shaft goes into ground water that is under pressure. Artesian wells have a static water level significantly higher than the water table and often do not even need a well pump. Wells into ground water that is not under pressure are just plain drilled wells.

Cities and towns (Milford and Amherst) rely on buying water from a public water supplier (Pennichuck). These public water suppliers get their water from a number of sources, rivers, reservoirs, and wells being the most common. Common perception is that these public water suppliers are tapping into sources unavailable to the public (rivers and reservoirs) because they are able to treat the water and clean it. In truth water utilities like Pennichuck rely heavily on groundwater wells. The only difference between their well and a private well is the size. The water and water source is the same.

Water companies obtain, clean, and deliver it to customers. They obtain water from natural sources, clean it, and pump it through their pipes to houses. People pay for the water, and the cleaning, and the pumping, and the water company must make a profit to stay in business.

Expected water use is planned for all types of customers. Water companies assume houses need 150 gallons/day/bedroom, with a safety factor of 2. In other words a public water company must have the capacity to provide a three-bedroom house with 900 gallons of water per day. Note that the company must have the capacity to provide that much water, not that normally any house ever uses that much water on a regular basis. Capacity requirements are defined by state standards.

Water companies must develop their water source and pumping capacity. In the case of water supplied from a well, a sufficiently saturated, permeable and porus aquifer must be located. (Stratified Drift Aquifers are generally the local source.) Hydrologists use ground penetrating radar to study potential sites to find potential aquifers. Such hydrologic studies can cost upwards from $5,000 to locate any potential water sources.

After the potential aquifer is located, the water company drills test wells. Public wells need to be able to pump roughly 60 gal/minute, with sufficient recharge to make this a constant rate even considering the drawdown and cone of depression caused by the drawdown. Assuming the source is good, and there is an acceptable pump site available with the necessary sanitary radaii, or buffer, generally this is about 200 feet.

The water company is required to have a site storage tank, steel or concrete, that stores between 4000 and 9000 gallons of water for each 30 bedrooms it serves. (Basically the storage tank must hold one day’s water for the customers; the exact requirements are determined by Department of Environmental Standards and are based on the customer base.)

The water company must also construct the pumping facility at the well site, and all treatment facilities to ensure that the water meets a uniform standard of quality. The quality is more stringent than for private domestic wells, and is monitered very closely to meet state requirments.

After the well, storage, treatment and pumping facilities are constructed the water company can begin to run pipe to the customers.

Water mains must be buried 5’ below grade. Bedrock must be blasted out when it blocks the way. The state does not permit watermains under its pavement. Watermains generally run along roads, houses get hooked up from the main as desired.

The cost of developing a water utility is not negligable. An uncomplicated hydrology study runs $5000 - $6000. A single well of the size and yield satisfactory for a water source could cost $35,000-$40,000. The pumphouse, controls and storage facilities would run $150,000 - $200,000. In otherwords a simple bedrock public well could cost $200,000 - $300,000 before the first foot of watermain is laid or variable operating cost is incurred.

The cost of laying watermain varies depending on the situation. Bedrock, state road frontage, existing road, new roads all present different situations. A general rule at this time is that laying watermain runs $50 - $75 per foot. If a house has a 200-foot road frontage, assume $10,000 to run the main along the frontage. This does not include the cost of hooking up the house to the main.

The cost of developing a new public water system is generally considered cost-prohibitive unless a grant is available. Sometimes State or Federal funds are available. The cost of running watermains is much less in a new development under construction and generally developers are the ones who install new mains.

There are instances where towns extend existing watermain systems to new areas, but generally it is the result of a developer generating the need and paying significant parts of the cost.

Homeowners eventually bear the cost. The average cost per year currently to the homeowner for being on an existing system is $300-400. In the case of the development of a new water system, homeowners benefiting pay the costs through both water rates, and through taxes. Towns typically set up a new taxing system specifically to tax for the public utilities.

Information about Sewage Disposal

Septic/Septic systems - Septic means poisonous. Septic system is the common term for household waste disposal systems.

Percolation - The "perc rate" is the rate at which water is absorbed into soil. This is important because water absorbed too fast will flow into the groundwater too fast. Water absorbed too slowly will not flow, and the system will back up.

House water usage - It is necessary to know the expected daily volume of waste flowing into a septic usage. Normally it is calculated in gallons/per/day. It differs somewhat from the expected water usage because not all water used is waste. Generally one figures between 130 and 150 gpd per bedroom, but other items need to be factored as well. For example, in some areas a garbage disposal is calculated to have the same waste disposal impact as a bedroom.

Septic Tank - Waste generally leaves a house and flows into a steel or concrete tank specially constructed for this use. The interior of the tank has a series of baffles which encourage solid wastes to settle, insoluble floating waste to be trapped, and the remaining fluid to trickle slowly out into the leach field.

Leach Field - The septic tanks drains its overflow liquid into a network of perforated pipe. This network of pipe is laid in sand. The liquid drips out of the perforated pipe and leaches through the sand. This network of pipes in sand is called the leach field. The field’s relative separation from groundwater levels, its freedom from interfering roots from nearby trees and shrubs, and the size of the field are all critical to the efficiency of the waste treatment.

D-box - Also called a junction box. The leach field is a laid out network of pipes. There is typically a central trunk with a series of radiating arms coming from a D-box on the central line.

Blackwater – waste water from toilets (and maybe kitchens)

Greywater – waste water from laundries and showers

All house drains connect and flow out into a large holding tank - the septic tank. Typically the system is gravity fed with the tank lower than the waste pipe as it exits the house. The tank itself normally holds more than 1500 gallons. Most modern tanks are made of reinforced concrete. The size depends on the number of bedrooms in the house and the expected volume of waste flowing into the tank.

Inside the tank is a series of baffles. The waste flows to the tank via an inlet pipe that discharges below the baffle level. The waste separates over time into three layers; solids on the bottom, lighter than water scum on the top, and "clean" water in the middle. It is an oxygen free environment, and bacteria are constantly at work converting the wastes to simpler forms. The top of the tank normally has three access locations that allow the tank to be opened for pumping and inspection. On the far end of the tank, the outlet pipe reaches down to the clean water level and is generally only an inch or two lower than the inlet pipe so the flow-through rate is slow. The outlet pipe, again gravity fed, flows out to the leach field. The solid-free "clean" water from the septic tank flows out into the leach field.

The leach field is a network of perforated pipes laid in sand-filled trenches. The wastewater from the septic field dribbles out through these pipes, filters through the sand, eventually down into the groundwater. Generally the bottom of the leach field (the bottom of the layer of sand) must be not less than 4’ above the highwater mark of the groundwater. The ground in which the leach field is constructed must also be of a soil type that allows water to perc not-too-fast and not-too slow. The soil type in which a leach field is constructed is extremely important.

The size of a leach field is determined by the expected volume of waste. The more bedrooms in a house, the bigger the leach field needs to be. The location of the whole septic system is dependent on the individual lot. The tank needs to be set away from the house, away from property boundaries, away from wells, away from wetlands or other areas of high water table, away from tree or shrub roots, and away from areas of heavy crushing traffic where the soil might be compressed and the pipes broken.

There are sites where there is no gravity-fed location and in those instances there can be a holding tank with a pump that pumps up to the leach field area. There are areas where fields need to be built up and placed in a mound because the natural water table would otherwise be too close to the leach field trenches. There are also areas where there is no place to site a safe leach field, instead one must use a holding tank which is pumped into a tanker and taken to a local waste treatment plant for disposal.

The inlet pipe and the outlet pipes must have their ends located in the clear water level between the organic solids on the bottom and the solid floating scum layer. If the outlet pipe is located in either the solid or scum layer the pipe will either clog backing the system up towards the house, or solid material will flow out to the field clogging the field. If the inlet pipe is located in either the solid or scum layer the inlet pipe could clog backing the waste system up towards the house.

To ensure the inlet and outlet pipes are in the clear zone it is necessary to pump the tank every few years and clear out the solids and scum. The frequency of pumping depends on usage, size of the tank, and kinds of waste. (Detergents generally inhibit the natural breakdown of the wastes and so the tank fills up faster.)

The leach field itself generally does not need maintenance. If the pipes and D-boxes are not crushed or obstructed it should last 20-30 years. If the tank is not pumped regularly, then solid wastes will flow into the field, clog the pipes and the soil, and the field will have failed. If the pipes are crushed or the D-boxes damaged waste will not be distributed; the field will become clogged and fail.

A failed leach field at its best looks like a very lush lawn, that smells and is mushy. At its worst a clogged leach field will clog the tank and waste will back up into the house.

After 20 or 30 years the sand in the field will begin to lose its porosity. It will cease to permit the waste water to leach through it. Even perfectly maintained systems eventually need the field replaced with fresh sand.