URBAN ACTIVITIES



 POTENTIAL WATER QUALITY PROBLEMS

Urban activities such as lawn fertilization, street sanding, sewage disposal, and construction can cause a number of water quality problems.  Sediment, nutrients, salts and bacteria may be increased.  Also, herbicides and pesticides as well as petroleum products and heavy metals may be carried to water bodies by runoff.  In some cases, stream temperatures may be elevated.

Increased sediment concentrations in waterbodies can impact fisheries and other aquatic life. This may include: less successful spawning activity; a change in the macro-invertebrate populations; and a change in the aquatic plant community.  

Increased nutrient concentrations can cause over fertilization of waterbodies creating a condition known as eutrophication.  This situation, which is often more serious in lakes than streams, results in excessive algal growth.  When the algae die and decompose, oxygen is depleted.  Depending on the extent of the oxygen depletion, a fish kill may result.  Increased nutrient levels can also impact water supplies that are used for human consumption. Elevated nitrate levels can interfere with the blood's ability to carry oxygen.  This can be a serious problem for infants and the elderly.  

Elevated total dissolved solids (TDS) concentrations, which may result from road sanding activities, can impact aquatic life and reduce the value of the waterbody for irrigation purposes.  

Elevated bacteria levels may result from municipal sewage treatment plants (a point source) and/or from on-site sewage treatment (a nonpoint source).  Some of these bacteria may be pathogenic.

Increased herbicide and pesticide concentrations as well as petroleum products can impact aquatic life.  Depending on the chemicals involved, a number of human health problems are possible.

For more information about the sources of these substances, please see page 5 of DEQ's 'Urban Best Management Practices'.

CRITICAL AREAS AND ISSUES

As with rural activities, the closer the urban activity is to a surface waterbody or ground water source, the greater the chance for a water quality impact.  However, because urban watersheds include numerous impervious surfaces and highly developed drainage systems, pollutant carrying runoff can come from great distances.  Project planners should carefully examine the drainage pattern and then exclude only areas that have closed drainage systems or  drain away from a public waterbody.  All other areas should be considered critical.

A number of urban management tools can be used to protect water quality.  They are outlined in the 'Making Improvements' section below.   However, before improvements are planned existing conditions should be assessed.

ASSESSING EXISTING CONDITIONS

When identifying pollutant sources, it is important to consider: type of land use including commercial, industrial or residential; soil type; topography; drainage patterns; precipitation patterns; lawn fertilization practices; street cleaning practices; traffic patterns; etc.

Identifying pollutant sources can be greatly facilitated by the use of maps.  While the level of detail of the mapping and assessment process may vary, additional attention should be given if any of the following exist:

  • There is a known water quality problem in a watershed.
  • Street sanding is utilized in the watershed.
  • Salts, to melt road ice, are used in the watershed.
  • High use road ways exist in the watershed.
  • The watershed has a large amount of impervious surface such as paved roads, parking lots, industrial complexes, malls, rooftops, etc.
  • A large amount of construction activity exists in the watershed.
  • Homes and businesses in the watershed are served in part, or entirely, by on-site sewage disposal systems.
  • Homes and businesses in the watershed are served by a community water supply system but not by a community sewage disposal system.

MAKING IMPROVEMENTS

Improvements, often called Best Management Practices (BMPs), fall into two broad categories: structural or management. A good water pollution control plan often contains both types of BMPs. Excellent sources of information for planning specific BMPs include:

There are many kinds of structural BMPs including: culverts; bridges; dikes; rip-rap; detention ponds; infiltration trenches; infiltration basins; porous pavement; storm water wetlands; sediment traps; check dams; sand filters; oil grit separators; runoff diversion channels; wet ponds; steep slope terraces; filter strips; etc. Depending on complexity, a detailed engineering drawing may be required.  In some cases, existing drawings provided by NRCS can be utilized or modified to fit a given situation.  (Also see drawings in DEQ's 'Urban Best Management Practices'.)

Management BMPs (sometimes called indirect management practices) include: landuse regulations; construction regulations; street sweeping; proper snow removal and storage; recycling; homeowner education regarding fertilizer, herbicides, pesticides, and lawn irrigation; cleanup campaigns; etc.  

FINANCIAL AND TECHNICAL ASSISTANCE

Section 319 funds are available from DEQ to assist with conservation practices in urban areas.  Applicants for these funds must show that a water quality problem exists and that the proposed practices will improve the problem. Interested parties should apply through their local conservation district.  The NRCS may have funds available through the Environmental Quality Incentives Program.  The Wyoming Game and Fish Department has funds for practices that benefit fisheries.

Technical assistance is available from local conservation districts, the Natural Resources Conservation Service, and the Cooperative Extension Service.  The Internet also contains a wealth of information including the following sites:

NPS Home | Identify Problem | Set Objectives | Plan BMPs | Obtain Funds | Implement BMPs | Evaluate