Who is Dictating Sewer Design – Developers or Designers?
Abstract:There are many attributes that utilities must evaluate when implementing good operation and maintenance (O&M) programs. One frequently overlooked factor is sewer design and inspection programs that are compiled based on the whims and special requests of developers rather than good engineering practices and inspection programs.
Developers impact city politics and programs in a multitude of ways. Developments bring money into the community, create and sustain jobs, and provide many benefits to the community. Developers have the ability to influence many people, including those in political offices and can quickly implement programs. However, the proposed development O&M costs may be higher than a typical sewer design. It is critical that utilities have programs that look at opportunities to reduce O&M costs during the design process.
Simple revisions to design, sewer ordinances, construction, and inspection and enforcement programs may save your utility money. Proper evaluation of these criteria will provide the utility with information to help make educated decisions regarding the best programs for their community. It will provide data to convince public officials that the special requests developers propose may not be in the best interest of the community.
There are several main criteria that impact the operation and maintenance of sewers. These are:
Capacity, minimum velocity
Cleanouts and locations
Materials for pipe, manholes, covers, laterals
Construction and Contract Completion
Construction inspection programs
CCTV and testing of sewers
Sewers ownership - private or public
Location of sewers is an issue that appears on the surface to be relatively straightforward but in reality tends to result in increased utility costs if the sewers are not placed in the right location. Many developers have a preference to locate sewers in easements located in residential backyards. Their argument to the community is that maintenance is not necessary if designed properly and if the utility or homeowner needs to replace their sewer– it will be less costly than digging up the paved street. This presents many unique issues known to utilities – but the cost factor of these decisions may not be properly accounted for. As many are aware, homeowners do not respect easements and everything from garages, storage sheds, decks, playground sets in addition to elaborate and sometimes expensive landscaping are located above sewers and manhole covers. In order to access the sewers to perform routine cleaning and inspection this becomes a logistical nightmare and include many hidden costs as outlined below.
Cleaning and inspection easement machine maybe required. To perform this activity using a special machine typically increases the crew size from 2 people to at least 4 people thus doubling the labor cost. Special equipment is required adding capital as well as maintenance costs for the equipment.
Manhole covers are inaccessible. If feasible the manhole could be not uncovered but this could result in purchasing longer lengths of hoses and lines for cleaning and inspection. Consecutive manhole covers that are inaccessible may require the need for a tractor camera. These cameras cost from 40,000 to 50,000 - four to five times the cost of a conventional CCTV camera.
Access to fire hydrants for cleaning programs may require additional hose or require tanker trucks for water use.
Notification of the homeowner to go on private property might be required in some communities resulting in costs associated with postage or site visits.
Fenced in backyards require notification of homeowner which might result in several trips to the home to get access.
Pets left outside with absent homeowners create another set of problems.
Ability to “restore” the property to the homeowners concept of what it was like before entering the property is not only time-consuming – it requires documentation of before and after.
These are some factors that relate to just one design issue. A more in-depth analysis of other design criteria will be presented including benefits and disadvantages as well as a range of costs to assist utilities in making informed decisions for their community
Document Type: Research Article
Publication date: January 1, 2003
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