5.1. Design & Construction

Tue, 09/18/2012 - 16:55 -- klm-admin

5.1.1. Rules for Planning the Site

Wastewater recycling facilities each have major variations according to the site, but some rules always apply:

  • Know the pathway and elevation where the collection system enters the site, including soil conditions underneath planned piping. Failure to account for this leads to disaster. If marshy or rocky conditions prevail where piping is planned, this may double construction cost and force realignment of elevations, causing water flow changes.
  • Avoid using pumps if possible - use gravity flow.
  • Use clay or compacted impermeable soil if possible
  • Know local agriculture and aquaculture before designing
  • Machine access: Each major component on the facility must be accessible by a back-digger or pump truck for servicing or modifications.

5.1.2. Mapping the site

Five maps are required: Location, Area, Site, Concept, Working drawings

The Location map shows the region where the site is located on a municipal road map, including compass.

The Area map shows an overhead projection of the local area served by the facility including:

  • compass
  • the surrounding neighborhood
  • the site
  • general patterns of collection system and rivers
  • where wastewater goes after it leaves the facility

The Site Map shows an overhead projection of:

  • existing trees
  • existing collection system
  • existing elevations
  • existing structures on the site
  • location of soil test drill holes
  • groundwater sources
  • legal boundaries
Location, area and site maps are completed before the final site is selected!

The Concept Drawings show overhead projection of:

  • planned slope also with a cutaway side view
  • planned ponds, with a cutaway side view
  • planned collection system on the site
  • planned site structures
  • biogas digester if planned
  • planned locations for livestock
  • planned flow pattern of water
  • planned garden areas
  • legal boundaries
  • fence

The Working Drawings show:

  • detailed structural plans for structures on site.
  • detailed structural plan of biogas digester
  • pond gate construction
  • garden irrigation system

Concept and working drawings are done after site selection. It is unnecessary to have detailed engineering for most working drawings unless required by local law except for the biodigester. This requires a separate set of drawings.

5.1.3. Staking the Site

To accurately complete concept and working drawings, each outline each structure with wooden stakes and string to show the perimeter of each pond & structure, according to the drawings.
This is done BEFORE completing detailed concept drawings, but AFTER dimensioning of the facility has been calculated and legal boundaries of the property are established. As construction proceeds, staking also occurs to guide workers regarding depth and slope, but this occurs later.

5.1.4. Planning Digester and Pond Levels

Correct levels ensure a smooth flow throughout the facility. Incorrect levels are a possible disaster if for example the outlet ends up higher than another water level on the site. Sequence for levels is explained in the Workplan.

5.1.5. Legal requirements

The law of contract is frequently ignored or contravened in many countries. For example city governments sometimes disregard contracts to pay for construction despite a full contribution by national and international NGOs. Contracted institutes and scientists often fail to complete their work without notice. Site operators sometimes do not complete their contractual obligations.

This is part of a culture taught hundreds of years ago by European colonial powers - low pay for bad work. It is changing but is still bad in many countries. If this goes on in your area, it is still necessary to have legal agreements to obey legislation, but direct personal relations with administrations and close control of sites takes priority over legal agreements.

Wastewater recycling facilities live beyond the life of most political administrations. It is necessary that a legal framework is in place before a change in governments. This is not a guarantee for success but it helps assure that when municipal governments change, the new administration has a clear framework to work with.

Go here for a list of legal documents. However, this documentation varies depending on land ownership, participation of a leading organization, and management. It is a good idea to have the advice of a local lawyer regarding contracts. However keep legal fees to a minimum and get a written estimate before having work done. Otherwise legal fees may create financial difficulties.

Table of Contents

Next Page