Management of Non-Point Source Pollution CE 296B

1
Management of Non-Point Source PollutionCE 296B

• Department of Civil Engineering
• California State University, Sacramento

Lecture 19, April 26, 1998 Management Strategies
- Part II
2
Recall where we left off
I. Categories of BMPs (cont.)

• A. Location with respect to where the pollution
  is coming from and where it is going
• Front of the pipe
• In the middle of the pipe
• End of the pipe
• BMPs that dont seem to be associated with the
  pipe at all.

? Here
3
Recall where we left off
I. Categories of BMPs (cont.)

• B. At the front of the pipe, categories could
  include
• BMPs that seek to minimize the use of a
  substance that could be a pollutant.
• BMPs that seek to adjust peoples behavior.
• BMPs that seek to keep pollutants in their
  place.
• BMPs that seek to prevent pollutants that have
  been mobilized from entering the pipe.

And Here ?
4
II. Front-of-Pipe BMPs (cont.) D. Keeping
pollutants immobilized. Two principle categories
come to mind here, BMPs associated with
construction and BMPs associated with existing
facilities. (cont.)

• 2. Existing Facilities. Many sub-categories
  exist here. Some are
• a. Cleaning up of spilled material ?
• b. Cleaning surfaces
• c. Maintaining vegetative cover
• d. Storing materials properly.

5
Cleaning-up Spilled Material-I

• In the course of human activities, materials are
  sometimes spilled onto the ground.
• When those materials could be a pollutant,
  clean-up procedures need to be implemented.
• There are several factors associated with quality
  clean-up procedures
• The people cleaning up a spill have to know that
  it occurred. The means of assuring each spill
  gets reported to the appropriate people in a
  timely fashion is difficult. This is probably
  the weakest link in most spilled material
  clean-up procedures.

6
Cleaning-up Spilled Material-II

• Factors associated with quality clean-up
  procedures
• The people cleaning up a spill must
• Be able to actually find the reported spill in a
  timely manner given the varied quality of
  reporting information.
• Have at their disposal the appropriate equipment
  to clean-up the spilled material.
• Have adequate knowledge of the material spilled

7
Cleaning-up Spilled Material-III

• Factors associated with quality clean-up
  procedures
• The drainage path to the receiving water from any
  patch of ground that is likely to be spilled upon
  picked at random must be known. In a large
  metropolitan area, having this kind of knowledge
  of the storm-drain system is very difficult.
• If the spill has entered the drainage system, the
  ability to intercept it should exist.

8
II. Front-of-Pipe BMPs (cont.) D. Keeping
pollutants immobilized. Two principle categories
come to mind here, BMPs associated with
construction and BMPs associated with existing
facilities. (cont.)

• 2. Existing Facilities. Many sub-categories
  exist here. Some are
• a. Cleaning up of spilled material
• b. Cleaning surfaces?
• c. Maintaining vegetative cover
• d. Storing materials properly.

9
Cleaning Surfaces - I

• One idea for preventing pollutants that are on
  the surface from becoming mobilized is to clean
  those pollutants off of that surface.
• On impervious surfaces, this has typically meant
  sweeping.
• Two types of materials are typically cleaned from
  a surface
• Trash
• Particulates
• With trash, this typically works fairly well.

10
Cleaning Surfaces - II

• Cleaning large particulate material, coarse sand
  and above, works fairly well also.
• The ability to pay for surface cleaning
  activities varies from one kind of public entity
  to another.
• Cleaning particulate material off of impervious
  surfaces has a problematical pollution control
  benefit. There is an equilibrium thickness of
  fine particulates that is difficult to change.
  Consider the animation on the following slide

11
Equilibrium Thickness of Fine Particulate Layer -
I

• Start with a perfectly clean surface.
• Assume that no wind is blowing.
• Watch the dust accumulate.

• Turn on normal wind conditions

12
Equilibrium Thickness of Fine Particulate Layer -
II

• Start with a completely clean surface
• Normal wind conditions exist
• Note the accumulation of particulates with time

13
Equilibrium Thickness of Fine Particulate Layer -
III

• Start with system at equilibrium
• Sweep the surface partially clean

• Repeat

14
Discussion Break

• What are the kinds of wind we have been
  talking about?
• Are there locations in an urban area that might
  collect a substantial amount of material through
  wind action?

15
Discussion Break

• Why is there a concern about cleaning up the
  fine particulate material off of impervious
  surfaces?
• With respect to non-point source pollution, what
  kinds of surfaces benefit more from sweeping
  operations? What kind less? Why?
• How much of a difference does a highly effective
  cleaning device make over a moderately effective
  device? Why?

16
Discussion Break

• There has been a suggestion in some quarters
  that to help meet TMDLs, an urban discharger
  might measure and count the pounds of pollutant
  in street sweepings.
• Does this mean that those pollutants have really
  been removed from the non-point source stream?

17
II. Front-of-Pipe BMPs (cont.) D. Keeping
pollutants immobilized. Two principle categories
come to mind here, BMPs associated with
construction and BMPs associated with existing
facilities. (cont.)

• 2. Existing Facilities. Many sub-categories
  exist here. Some are
• a. Cleaning up of spilled material
• b. Cleaning surfaces
• c. Maintaining vegetative cover ?
• d. Storing materials properly.

18
Maintaining Vegetative Cover

• Many surfaces in urban locations, both public and
  private, are covered with vegetation that holds
  sediment in place.
• Establishing vegetative cover where it does not
  exist and maintaining existing cover is the focus
  of much non-point source pollution effort in
  urban areas.
• In California, maintaining vegetative cover
  usually requires irrigation. This potentially
  produces a flow stream during dry weather that
  could be considered non-point source pollution.

19
Discussion Break

• A chic idea is to use California native plants
  for vegetative cover. One of many positive
  attributes to this idea is that California native
  plants are by nature drought resistant and
  require less irrigation. Several problems do
  exist though
• Is it worth the expense of keeping out exotic
  plants?
• During drought conditions, many native plants
  provide less cover, making it possible that
  erosion would take place. How does this fit with
  the context of the CWA?

20
II. Front-of-Pipe BMPs (cont.) D. Keeping
pollutants immobilized. Two principle categories
come to mind here, BMPs associated with
construction and BMPs associated with existing
facilities. (cont.)

• 2. Existing Facilities. Many sub-categories
  exist here. Some are
• a. Cleaning up of spilled material
• b. Cleaning surfaces
• c. Maintaining vegetative cover
• d. Storing materials properly. ?

21
Proper Material Storage - I

• Many items that are pollutants are pollutants if
  they find their way into a receiving water have
  legitimate uses. As these items are stored for
  use the idea is to prevent them from becoming
  mobilized in a flow stream. Examples include
• Aggregate piles
• Sacks of fertilizer
• Containers of herbicides, pesticides, or
  fungicides
• Petroleum products

22
Proper Material Storage - II

• BMPs associated with proper material storage
  direct that techniques specific to the
• Material in question
• Particular use of that material
• Location of that material
• Be devised.
• The list of such techniques is endless, but
  includes
• Placing a tarp over aggregate piles
• Storing materials on a pallet
• Construction a berm around a storage area.

23
III. Middle-of-Pipe BMPs

• A. Recall our drawing defining what the pipe is

Pipes
Polluting Activities
24
III. Middle-of-Pipe BMPs (cont.)

• B. The idea of middle-of-the pipe BMPs is to
  arrest the movement of pollutants that have found
  their way into the non-point source pollutant
  stream on its way to a receiving water. These
  can be BMPs that
• 1. Hold the pollutant in place until it can be
  retrieved.
• 2. Make the pollutant part of the pipe

25
III. Middle-of-Pipe BMPs (cont.)

• C. Storm drain type pipes. Basic engineering
  principles used in the design of storm drains
  insure an efficient transport of pollutants.
  After all, the point of most storm drains is to
  get the water away as efficiently as possible.
• Thus, devices in storm drains to intercept
  pollutants have an uphill battle to fight.
• The most often discussed item here is a catch
  basin and variations on that theme.

26
Catch Basin Usage - I

• Picture to be inserted by tonight.

27
Catch Basin Usage - II

• The basic problem with this idea is the extremely
  short detention time. It is often less than one
  second meaning that only very large and dense
  items will be trapped.
• Rocks are typically not thought of as
  pollutants.
• Cleaning costs can be extremely high as well.
• A variation on the theme of a catch basin is the
  use of filtering inserts placed in the basin.
  These inserts made up of adsorbent material are
  designed to trap fine particulates and dissolved
  constituents.
• The maintenance on these is appalling.

28
Discussion Break

• Periodically, the use of catch basins are
  studied as a means of reducing non-point source
  pollution (going back decades). The conclusions
  are usually the same.
• Despite this, they still keep coming back as a
  suggested BMP.
• Why do you think this is?

29
Discussion Break

• How could these type devices serve to enhance
  the propagation of disease vectoring?
• If they did improve water quality, how would you
  compare those benefits with the detriments of
  increase disease due to insect vectors? What is
  the equation?

30
III. Middle-of-Pipe BMPs (cont.)

• D. Small water course type pipes. These can be
  flood control type channels (the classic concrete
  trapezoidal channel) or small, often ephemeral,
  streams.
• A popular, but expensive idea is to reestablish
  or enhance existing riparian habitat. Wetlands
  restoration is particularly popular.

31
Discussion Break

• As mentioned in the previous slide, this is an
  expensive process. If multiple benefits could be
  established for such a process the probability of
  securing adequate funding improves.
• What are other benefits of constructing BMPs
  that enhance small water courses?

32
III. Middle-of-Pipe BMPs (cont.)

• E. Overland flow type pipes. When water flows
  over a grassy slope in a thin sheet, substantial
  pollution control benefits may accrue. Among
  them
• 1. Removal of sediment
• 2. Removal of conventional organics
• 3. Removal of nutrients (if the grass is mowed
  and removed to a landfill)
• 4. Removal of metals (somewhat temporary though)

33
III. Middle-of-Pipe BMPs (cont.) E. Overland
flow type pipes. (cont.)

• Problems include
• 1. Irrigation requirements, in an arid region
  this may mean several feet of water.
• 2. Maintenance requirements.
• 3. Possible disposal problems associated with the
  clippings if they contain metals.
• 4. These systems only work well if the grass is
  of a particular height. What if the grass is too
  long when it rains?