This book is intended to assist property owners by informing them that there are numerous types of sewage disposal systems available.

Dingman Township is not served by central sewage (city sewers). As such, you will need to construct a sewage disposal system on your own property.

It is the purpose of this document to provide the reader with information to assist in making an informed decision about which type of sewage disposal system is best suited for their property. The document was intended for use by the layman, particularly those who have no prior experience with on-lot sewage disposal systems. The reader is advised to seek professional guidance (e.g.. attorney, soil scientist, engineer, etc.) as may be required prior to applying for a sewage permit.

The Sandmound Myth.

It is commonly believed that the elevated sandmound is the only sewage disposal system that may be used in Dingman Township. Nothing could be further from the truth. After sewage testing is performed on the property, the property owner may choose from a menu of sewage options based on the test results. In the past, the menu was quite limited and the elevated sandmound was usually the least expensive, least obtrusive, and best functioning system that was available at that time. Today, the property owner has over 50 types of sewage disposal systems (including variations) to choose from, many of which are quite superior to the sandmound.

Side view cut away of an elevated sandmound

Why Not a Sandmound?

Most people agree that the elevated sandmound is ugly and obtrusive. But the biggest drawback is not as obvious. When the sewage effluent is pumped into an elevated sandmound, it often contains suspended solids. The solids pass through the aggregate and are filtered out by the sand. Under normal circumstances, the sand holds these solids while decomposition takes place. If the suspended solids collect at a rate greater than they can decompose, a semi-permeable bio-mat develops. As the effluent flow is restricted, pressure builds in the mound. Eventually the effluent will push though the point of least resistance and a leak develops. The mound can be repaired, but such repairs are costly and often result in destruction to the property’s lawn and landscaping.

Many of today’s systems employ a filter between the septic tanks and the dosing tank. The filter catches suspended solids before they get to the aggregate. In the event that the accumulation of solids exceeds the rate in which the solids decompose, the filter can be cleaned --- a relatively inexpensive procedure.

 

Elevated Sandmound with Excessive Bio-mat

Why are Sandmounds So Common?

There are three reasons why elevated sandmounds remain the sewage disposal system that is permitted most often in Dingman Township.

Property owners are not aware that they have other options.

Real estate sales people and housing contractors are more familiar with the elevated sandmound and are more comfortable promoting systems that they are familiar with.

Sewage system designers often promote the elevated sandmound over other systems because they are easier to design.

 

Factors to Consider when Choosing a Sewage Disposal System

Soil testing is performed on the property in the area where the system is to be sited. After the soil testing is completed, the property owner should examine the available system options and investigate the following points:

A Brief Review of Some of the Options Available

The following is a list of just some of the systems available that may be used in place of an elevated sandmound. The information has been kept general as each site must be evaluated on a case-by-case basis.

At-Grade Bed

This system requires a primary treatment tank (septic or aerobic), a dosing tank and a bed of aggregate placed directly on the ground. The aggregate may either be placed to level the slope or it may be placed with the top of the aggregate parallel to the ground.

• At-Grade Bed with Peat Bio-Filter

This system is the same as the At-Grade system previously discussed with one major difference. A peat bio-filter is located between the primary treatment tank and the dosing tank. The peat bio-filter is essentially a box filled with specially graded peat moss. The effluent is filtered through the peat moss which provides a very high level of treatment.

 

Limiting Zone                 20” min.                                    20” min.

Average Perk Rate         3 – 180                                     3 – 180

Slope                             12% max.                                12% max.

 

 

At-Grade Bed with Free Access Gravity Sandfilter

Once again, the same as the At-grade system described in #1 (above) only instead of adding a peat bio-filter, the system utilizes a free access gravity sandfilter. A free access gravity sandfilter is constructed using a filter tank (similar in size and construction as a septic tank), gravel, and specially approved sand. It only takes about one hour to construct the filter on the house site. After construction, the property owner is responsible for maintaining the system. Typical maintenance takes about 5 minutes every 3 months.

 

Basic Requirements

 

                                At-Grade with FAGSF                Elevated Sandmound

Limiting Zone                      20” min.                                     20” min.

Average Perk Rate              3 – 180                                      3 – 180

Slope                                 12% max.                                  12% max.

 

Drip Irrigation

There are many ways to design a drip irrigation system. Some employ septic tanks, others aerobic tanks. Some employ sandfilters. Others do not. All systems utilize a hydraulic unit, dosing tank, and drip tubes. The system has three big advantages. First, the drip tubes are completely buried – no unsightly mound! Second, there is very little digging. A slit is cut into the ground, the drip tube is placed in the slit, and then the slit is closed. Trees, rocks, etc. are left in place keeping the natural beauty of the woods. Finally, the tubing may be laid in a myriad of shapes allowing the system to be sited in areas that may otherwise not permit a system to be sited.

 

Basic Requirements

 

                                    Drip Irrigation                    Elevated Sandmound

Limiting Zone                   20” min.                                      20” min.

Average Perk Rate         not required                                   3 – 180

Slope                              25% max.                                    12% max.

 

Individual Residential Spray Irrigation System

 

Individual Residential Spray Irrigation Systems (IRSIS) filter then chlorinate the sewage. The treated sewage is then sprayed onto the natural vegetation. The biggest drawback to the use of this system is that it requires a fairly large property. Spray field size varies based on the amount of usable soil, the slope of the land, and the type of vegetation growing on the site. The minimum spray field would be 10,000 square feet.

 

Basic Requirements

 

                                      IRSIS                               Elevated Sandmound

Limiting Zone                  10” min.                                  20” min.

Average Perk Rate       not required                                3 – 180

Slope                             25% max.                               12% max.

 

Profiles drawn show the components found in a typical system for the system types previously noted.

Elevated Sandmound

House, septic tank, dosing tank, mound.

House, septic tank, sandfilter, dosing tank, at-grade bed

House, aerobic tank, sandfilter, chlorine contact/dosing tank spray field

Note: Spray heads would normally be spaced 100 feet apart. Actual spray field would range from ¼ acre to 2 acres for a 3 bed room house.

Note: Only tank accesses and spray heads are above ground.

House, aerobic tank, dosing tank, hydraulic unit, drip field.

Note: Only tank accesses and hydraulic unit are above ground.  Drip tubing and return lines are completely underground.