As the pressure mounts to address the housing crisis with more residential development, one limiting factor stands out: the water supply.
The growth pattern recommended by the state, and echoed in the Town Plan, is “smart growth” that adds housing density in villages and their immediate surroundings. Rural sprawl is strongly discouraged. And, indeed, many towns already have dense village centers. They were able to build that way because they possess a centralized water system.
Thetford is somewhat unique in that there is no town center. Rather there are seven villages that are geographically separated. Some of those villages do have private water systems that serve multiple homes.
To better understand present water supplies and plan for the future, the Town commissioned a study on its water systems from Stantec Engineering using funding from a municipal planning grant. Existing water systems in Thetford are summarized in the resulting 154-page Report on Community Water Systems.
As shown in the table, most of the water systems serve a small number of users through narrow pipes, some running from holding tanks fed by springs. Wells provide the water for the Thetford Water Co-op on Thetford Hill, the East Thetford Water Co., the Post Mills Water Co., and the North Village Water Co. in North Thetford and the two school systems. None of these systems has the capacity to provide fire protection. According to the Report, a water supply for firefighting must deliver between 500 and 12,000 gallons per minute.
Water systems with narrow pipes have low water pressure; therefore those homes utilize basement storage cisterns to compensate. A trickle of water fills the cistern, and a pump lifts and pressurizes water to the rest of the house. Cisterns store several days’ worth of water and are an old, traditional home water supply. They are still used, for instance, to collect rain runoff in dry areas of the country where water conservation is critical. However the Vermont Water Supply Rule “does not allow the use of cisterns,” citing risks of contamination from bacteria and foreign objects falling into the cistern. Instead they call for changing to water mains to provide the correct water pressure.
Such a change is not for free. The Report states, “the private costs associated with the removal of the existing basement cisterns could be on average $12,000 per user” based on an average 50-ft connection to a public water supply.
Certainly water mains in villages would make it possible to build central in-fill housing and clustered development at village margins. But the prospect of changing to water mains brings up many questions. In what location would Thetford build water mains? There is no one center of population, unlike in neighboring Fairlee where water mains have allowed a dense mix of housing and commerce to flourish in the downtown.
Based on discussion with town officials, planned changes to Zoning Regulations, and considering natural resource limitations on developable areas, the villages with the most promising potential for growth were deemed to be Post Mills, East Thetford, and North Thetford. However, the cost of a water mains system shared between even two of these non-interconnected villages would be very steep. Post Mills lies distant from the other centers and would need its own water mains.
EXISTING WATER SYSTEMS AND POTENTIAL NUMBERS OF USERS;
Union, North Village and South Village Water Co.s are in North Thetford
There is also the question of where a system of water mains would obtain its water. Existing detailed maps of aquifers in Thetford are not readily available. According to an “approximate map” of well yields in Vermont from the VT Geological Survey, most of Thetford has a projected well yield of 10-15 gallons per minute, dropping to 2-9 gallons per minute near the Connecticut River. The river itself was considered as a potential water source; however its large watershed area encompasses likely contamination sources with a broad array of pollutants. The cost of treating river water to meet drinking water standards is anticipated to be greater than developing an additional well as a water source. However, even wells need some water treatment. The water from the relatively new well supplying the East Thetford Water Co. is treated with liquid chlorine injection and is scheduled to have additional treatment installed for pH (acidity/alkalinity balance) and removal of the heavy metals iron and manganese.
The town will have to prospect for water to locate sources with adequate yield in the vicinity of North Thetford and Post Mills. This would involve hiring a consultant to detect and map fractures in the bedrock that may yield water and then paying for some test drilling. The East Thetford Water Co. is fortunate to have a 505-ft deep drilled well with an estimated yield of 25.5 gallons per minute. However, even this is not sufficient for fire protection. To suppress an average sized house fire requires 60,000 gallons of water at 1000 gallons per minute.
The Report states, “Water main infrastructure to provide an 8-inch water supply pipe, valves and hydrants to provide a water system that is capable of fire suppression flows and pressures can be anticipated to cost roughly $1.3 million per mile.”
Apart from the prospecting work, the replacement of existing low-flow, low- pressure systems would be a significant expense. For instance, Stantec anticipates that just to replace the spring-fed systems (Union and South) for 41 users in North Thetford with a community well and water distribution mains may cost between $300,000 and $700,000. However, there are a lot of unknowns and variables, such as the well depth and location, the required water yield for the whole system, the cost of building the infrastructure and improvements for access and installing all the pipes, pumps, valves etc needed to convey the water from well to users.
Likewise, increasing the water mains size to give more pressure within the existing systems seems cost-prohibitive without outside funding. Stantec based their calculation on existing pipe running for 0.5-1.0 miles to serve between 9 and 22 properties. The average separation between users is 250 feet.
AVERAGE COST PER USER TO INCREASE WATER MAIN PIPE SIZE
BASED ON 250 FT SEPARATION OF USERS
LF = linear feet
Once villages begin any system replacement they will be held to the strict demands and regulations of the Water Supply Division (WSD) of the Agency of Natural Resources. In the past the WSD has been less than benevolent to Thetford water companies, for instance ordering Union Water Co. to commission a hydraulic analysis just to get a permit to operate. This cost the Company almost a full year’s worth of dues. The WSD also ordered the Company to obtain an engineered design that replaced the cisterns and booster pumps because they do not meet the WSD’s rules. That design ate up another year’s worth of dues and concluded it would cost $500,000 for only 20 houses to replace cisterns with water mains and a well. This spending did nothing to improve the actual water quality. (The $ figure is from many years ago; prices have risen dramatically since then. It does not align with Stantec’s much lower recent estimate in the previous paragraph.)
Another potential solution to bringing North Thetford’s water up to standard is suggested in Stantec’s Report. This would be to run a pipe downhill from the Thetford Hill Water Co-op’s well to North Thetford Village, a cross-country distance of at least 1.2 miles. The difference in elevation would provide the necessary water pressure. Under this scenario, it is possible that more wells would have to be drilled on Thetford Hill to keep up with demand. It would also require permission from private landowners whose land the pipeline would cross
There are many decisions to be made about water. Firstly, how to best upgrade the spring-fed systems into a modern, State-compliant system. Then, what location(s) to target for additional housing, and thus where to build out additional water infrastructure. More build-out in Post Mills will require a whole new water system, as the current one in South Post Mills was sized only to replace wells contaminated by the former landfill. And a most important piece of the puzzle will be where to find the funding, because this will be very expensive. Among several potential funding, some are available only to municipalities rather than private water companies, which raises the issue of whether the Town, and thus the taxpayers, should take ownership and shoulder the financial responsibility for communal water systems. And not to stop there, the old model of volunteers running and maintaining water systems has run its course. New and upgraded systems will need more professional — read paid — management as well.
Photo credit: Li Shen