Water and Sewage Sumter SC
Water and Sewage
In the last issue, we discussed getting access (road or driveway) and electricity to a building site. In most states a plot of land is not considered buildable - you won't be allowed a building permit - unless it is served by a sewer line or the soil is acceptable for on-site sewage disposal. This brings us to the remaining site services: water and sewage. WATER If you buy bottled water, you've seen distilled water on the shelves as well. The process of distillation - evaporation followed by condensation - removes all impurities from water, making it pure and nearly tasteless.
Illustration 1 shows nature's great still, the hydrologic cycle, wherein water molecules evaporate from the surfaces of plants, puddles, lakes and oceans, rise into the atmosphere and fall again as condensed rain or snow. As the rain falls, it dissolves carbon dioxide from the atmosphere and becomes slightly acidic (containing carbonic acid). Unfortunately, as more pollutants are added to the atmosphere from industrial and power plants, rain downwind of these sources is becoming increasingly acidic and otherwise impure. Some of the rain and snowmelt runs off the surface and collects in streams and surface ponds (A). What doesn't run off or evaporate sinks into the ground as groundwater. The dashed line shows the water table, the level at which the ground is saturated with water. Due to the extremely slow horizontal movement of groundwater, the water table tends to follow the surface of the ground, although it rises and falls with rain and drought. Water below the minimum level of the water table, and therefore independent of the season, is called an aquifer. When an aquifer breaks the surface, the water flowing from the earth is called a spring (B).
If our site isn't close to a public water main, we can also reach water in the ground through wells: digging a pit until we reach the water table (C), driving a pointed pipe through sand to the water table (D), or drilling through solid rock to an aquifer (E). To a city person, a well sounds pretty primitive, but that is how 15 million U.S. households get their water. Water Quality Table 1 lists problems that can plague drinking water and what you can do about them. Unless you live on the shore of a large lake in an unpopulated area, a surface pond or lake is usually a bad bet. Typical pond water contains sediment from streams, algae and parasitic cysts, organic compounds from decaying vegetation, and bacteria. If you live downwind of a major industrial area, both surface water and groundwater may be acidic. Acid water dissolves calcium and magnesium from limestone and marble, leading to hard water in more than half of the United States (Illustration 2).
Acid water also dissolves iron and manganese, leading to red and black water stains on your fixtures. A rotten-egg odor is most likely due to decaying organic matter but may also be caused by sulfur in the ground or by industrial pollution. Though we think of soil as dirty, the earth actually purifies water of pathogens. As water slowly percolates through the fine soil, solids are filtered out, anaerobic bacteria (in the absence of oxygen) are killed by the oxygen in the unsaturated soil, and then aerobic bacteria (in the presence of oxygen) are killed by lack of oxygen at deeper levels. Finally, in an aquifer, in which water may reside for hundreds or thousands of years, even viruses expire. So we have opposing actions: The earth adds dissolved minerals at the same time that it is removing pathogens. Well Options The oldest type of well is dug - simply a lined hole in the ground. Many such wells are still providing excellent water 100 or more years after they were dug.
It's not as backward as it may seem. Just make sure the water table will remain at least 4 feet above the bottom through the worst drought. In the days before power equipment, wells were dug by hand. One person stood in the hole, filling a lowered bucket with soil, while a helper at the surface emptied the bucket. A more modern and much safer method, possible when the water table is within 15 feet of the surface, is excavation and setting of round, concrete well tiles with a backhoe. In this case, a very large hole is excavated to the maximum reach of the hoe. Provided the hole fills with water, crushed stone is spread on the bottom, the well tiles placed, the hole backfilled with clean sand, and the area around the well covered with a sloping and impervious material, such as clay or concrete. In areas of deep sand and a reasonably shallow water table, driven-point wells are the best option. The sand acts like a giant filter, clarifying and purifying the water.
The well consists of a sharp wellpoint with very fine slots (smaller than the sand grains) driven to below the level of the water table by pounding on the end of coupled lengths of galvanized pipe. In any area where driven wells are common, professional well-driving companies will be found. Illustration 3 shows the most common well, and the one usually most satisfactory. A 6- or 8-inch-diameter hole is drilled through rock in search of a water vein or aquifer below the water table. A submersible pump is connected to polyethylene pipe and electric cable of lengths equal to the well's depth, less an allowance for bottom debris. A rubber "snubber" is expanded to fit the inside of the pipe to center the pump and keep it from twisting, and the whole thing is lowered into the well. Not shown is a safety rope attached to the pump, in case the pipe connection fails. At the top the pipe is connected to one half of a pitless adapter. The pitless adapter is a bronze fitting through the well casing below the maximum level of frost.
It keeps the pipe from freezing and allows the pipe/cable/pump assembly to be removed easily. The water storage tank, pressure switch and pump control can be located in a pump house at the well or inside the building. Drilling wells can be an expensive and risky business. The deeper the well, the more likely it is that the water will be unpolluted. But the farther one drills, the less likely it is that water will be found. Many a 500-foot dry hole litter the countryside. At $5 to $10 per foot, some homeowners are driven to using dowsers, who claim to be able to divine the location, depth and flow rate of aquifers. However, much as my romantic soul might wish to believe in such mystic abilities, it simply cannot. I tried mightily once, but the old geezer let me down. I had struck a fixed-price deal with a "straight" driller for a minimum of 1 gallon per minute. I then called a local dowser much acclaimed for his ability to find missing persons as well as water.
Happily, he also ran a well-drilling company as a sideline. On the appointed day, the old fellow cut a fresh alder branch, assumed the well-known position, and tacked back and forth across my site. After a half-dozen passes he proclaimed a vein at 90 feet that would undoubtedly produce l0 gallons per minute. Interestingly, his vein crossed the exact spot where the other driller proposed to drill. Intrigued by the coincidence, I asked if I might try the rod. Furthermore, in the interest of science, might I be blindfolded? So, blindfolded and guided by the dowser's directions, I too crisscrossed the site. And damned if the rod didn't seem to dip of its own accord at the very same spot! Needless to say, the validity of my MIT-instilled scientific philosophy seemed in jeopardy. At this moment of crisis, however, a certain thriftiness passed on by my Scottish maternal grandfather prevailed. "How certain are you of this vein?" I asked cagily. "Haven't missed one yet." (An impressive answer considering the age of the old coot.) "Well, then, you would be willing to guarantee the well for a fixed price, wouldn't you?" "Never guarantee anything. Against principles." So I still don't know.
But without further proof, I recommend waiting until the dead of winter when most well drillers are sitting around wondering how they're going to make the next payment on that $250,000 rig in the yard. Tell each you are going for the lowest fixed-price bid from all the well drillers in the area, then wait by your phone. Flow Rate One gallon per minute doesn't sound like much. It isn't if you are watering the lawn, but multiply l gallon per minute by 60 minutes and then by 24 hours and you'll find (Illustration 4) that it adds up to 1,440 gallons per day. Furthermore, a 6-inch-diameter well stores 1.5 gallons per foot, or 150 gallons for the average drilled well. The average person consumes 75 gallons per day without water conservation, so the daily amount is adequate for any family. However, watering a lawn or garden, or mindlessly leaving the water running for hours on end, may run a 1-gpm well dry. Freezeproofing Nearly everyone north of the Mason-Dixon Line has experienced frozen pipes at least once.
Having suffered every possible variation, I'm somewhat of an expert on the subject, and I can say with some assurance that there is only one foolproof way to avoid frozen water pipes. That is, as shown in Illustration 3, to bury the supply pipe beneath the maximum frost depth. Illustration 5 shows the maximum frost depth, in inches, across the United States. What the map doesn't show is that the soil beneath roads and driveways will freeze as much as 2 feet deeper because of the lack of an insulating snow cover and the higher conductivity of the compacted soil. If you are too close to bedrock to bury the pipe as deep as the map suggests, there are technological solutions that will at least increase your chances. Illustration 6 shows a water pipe running close to the ground over a shallow ledge. Above it are panels of rigid extruded polystyrene (blue Styrofoam). This rugged and waterproof foam acts like snow cover in retarding the escape of the earth's stored heat. Each horizontal foot of the foam has approximately the same effect as a foot of burial, so the installation shown provides the same protection as burying the pipe 3 feet deep. The foam panel technique shown is more foolproof than insulating the pipe with a foam sleeve, for the following reason.
A foam sleeve merely retards the loss of heat from the pipe. As long as water is drawn from the well several times each day, the well water never cools to the freezing point. If the homeowner goes away for a week, however, the water in the pipe will freeze. In contrast, the foam panel is retarding heat loss from the earth. The amount of heat stored in the earth is effectively infinite, so the pipe surrounded by the earth beneath the foam will never freeze. SEWAGE DISPOSAL About 0.1 percent of sewage is solid, the remaining 99.9 percent being water. About 40 percent of private sewage comes from the 5 gallons we flush down the toilet every time we pull the handle. The other 60 percent comes from bathing, clothes washing, dish washing and cooking. Altogether, the average person uses 100 gallons per day around the home. (With the new 1.6 gallons-per-flush toilet, the average is closer to 75 gallons per day.)
It is easy to think of this huge volume of water as a pollutant. But it is a pollutant only if we mismanage it, if we fail to safely dispose of the small number of pathogens it contains. Sewage treatment can be performed on a massive municipal scale, or it can be done in your own backyard. Twenty-two million American families have private sewage treatment systems, so you can see you will not be alone or without help if this is what your site requires. The operation of a municipal treatment plant is so massive that the effluent has to be dumped into a lake or river. Since the treatment is never 100 percent complete, the remaining chemicals necessarily pollute these bodies of water to some extent. Municipal treatment plants also have to speed up the natural processes involved in sewage breakdown; otherwise the treatment plant would cover a considerable percentage of the town. The treatment plant heats, stirs and aerates (adding oxygen to) the sewage. The sewage-disposal system in your own backyard operates on the same biological principles, except it is completely passive. The Septic Tank Except where a septic tank must be at a greater elevation than the lowest fixture, the raw sewage flows from the house to the tank through a 4-inch PVC house drain sloped at 1/4 inch per foot (Illustration 7).
In the tank, grease and whatever else is lighter than water floats at the top as scum. Solids heavier than water settle to the bottom. The tank is sized (Table 2) to retain the water in the tank for several days, allowing time for the solids to either float to the surface or sink to the bottom. The septic (from the Greek septikos, meaning rotted) tank contains anaerobic bacteria. These bacteria are present in nature and don't have to be added by you, even when the tank is new. The bacteria decompose the solids, reducing their volume by half. Better septic tanks contain two chambers to maximize decomposition and reduce the chance of solids leaving the tank. Increasingly, sanitary engineers are also recommending a septic filter after the tank or in the second chamber to prevent solids larger than 1/16 inch from clogging the drain field. In the drain field, the liquid effluent is distributed along the lengths of level pipes with holes in the bottom.
As the effluent percolates downward through a bed of stones, any pathogens not killed by the anaerobic bacteria are set upon by aerobic bacteria, altogether achieving a rather complete slaughter. The effluent is further filtered and purified as it travels downward through the soil toward the water table and upward to be evaporated to the atmosphere. If the site of the drain field is remote or higher than the outlet of the septic tank, the effluent first flows into a pump chamber, where it is periodically pumped up to the level of the field. The effluent pump has proved the salvation of many a tough building site, allowing the drain field to be as much as 1,000 feet from the house. If left in the tank, the solids could build to the level of the outflow. At that point, raw sewage would flow directly through the tank to the drain field and clog the pipes. When this happens the old field must be abandoned and a new one constructed at great expense. Septic tanks should therefore be pumped out on a regular schedule, as shown in Table 3. Mound Systems When the site doesn't provide at least 24 inches of original inorganic soil of the proper drainage characteristics, or when the seasonally high water table (generally the level of the water table in spring) or bedrock is too close to the surface, the conventional leach field of gravel-filled trenches is prohibited. Provided there are at least 18 inches, a designed mound of soil may be added over the site soil (Illustration 8).
As with a conventional trench system, the base area of the mound system is sized to the expected amount of effluent. The usual rule of thumb is to assume 120 gallons per day per bedroom and to require 1 square foot of drainage area per gallon per day. Thus, a two-bedroom home would require 240 square feet of trench or mound base area. A mound system must be designed by a state-licensed sanitary engineer or soil scientist, and it must be constructed exactly as designed. The mound is the most common of dozens of engineered leach fields, but your codes official or soil evaluator may have an idea better suited to your particular site conditions. Setbacks Whether you have a conventional trench-type leach field, a mound system, or some other engineered system, the leach field is subject to several setback requirements:
20 feet from the house foundation
10 feet from property lines and driveways
100 feet from a water well
75 feet (in some states more) from a stream or water body
25 feet from a drainage ditch or swale In addition, most state codes require that the site contain an additional area of acceptable soil for the likely case that the original leach field will some day have to be replaced. As you can see from Illustration 9, on-site sewage and water require careful site selection and layout to satisfy all of the numerous code requirements. Check with your code officials to make sure your local requirements aren't more restrictive than those listed here. Assuming your site meets all of the requirements so far, we will next begin the fun part - the preliminary design.