Module 1: Construction Site Erosion Control

Transcription

1 Module 1: Construction Site Erosion Control Problems and Regulations Robert Pitt Department of Civil, Construction, and Environmental Engineering University of Alabama Tuscaloosa, AL Problems Associated with Erosion of Construction Sites Construction site erosion rates in the US range from about 20 to more than 200 tons per acre per year. These rates are about 3 to more than 100 times greater than erosion rates from croplands. Construction site erosion rates vary depending on local rain energy, soil, and topographic conditions, plus the use of effective erosion controls. Increased Construction Site Erosion Causes Many Problems: Highly turbid receiving waters adversely affects aquatic life (gill abrasion, decreased light penetration, can t see predators or prey, etc.). Stream sedimentation destroys habitat (smothers food sources, destroys spawning areas, etc.). Decreased aesthetics along linear parks (highly turbid waters can persist for several days after a rain). Damage to construction sites require re grading. Decreases real estate sales opportunities in affected areas. Causes ill will in surrounding areas that are adversely affected. Adversely Affects Real Estate Sales

2 Damages Property Bad Publicity and Ill Will of Neighbors Increased Stream Turbidity Stream Sedimentation

3 Clogged Culverts and Increased Flooding Fugitive Dust and Associated Traffic Safety Problems Sediment Sources WI DNR photos

4 Major Sediment Sources at Construction Sites Eroded slopes and channels Long term exposed/bare soil Improper site activities and waste disposal practices Unprotected storage piles Construction activity near roadways Construction in streams Eroded Slopes and Channels

5 WI DNR photo Long Term Exposed/Bare Soil

6 WI DNR photo Heavy Sediment Loadings on Streets in Construction Areas Working Near Streets

7 Storage Piles Improper Site Activities Fuel Spillage Improper On Site Waste Disposal

8 Working Near Streams and in Channels Stream erosion first season after new outfall for subdivision expansion Early Regulations The Refuse Act of 1899 (33 USC 407) was used in 1970 to establish a discharge permit system (Public Law ). This act prohibited the discharge of any material, except sewage and runoff, into navigable waterways without a permit from the Dept. of the Army.

9 Size of Water Amendments to the Water Pollution Control Act (92-500) 1956 (making the legislation permanent and to fund construction grants for POTWs), 1961 (increased funding for water quality research and construction grants), 1965 (increased construction grants and started research concerning combined sewer overflows), 1966 (removed the dollar limit on construction grants), 1972 (the most important advances to this date; act renamed Clean Water Act ), 1977 (to extend some of the deadlines established in the 1972 amendments), and 1988 (require discharge permits for stormwater). TMDL Regulations Another important regulation affecting drainage and stormwater quality is the TMDL program. The TMDL program is aimed specifically at assuring attainment of water quality standards by requiring the establishment of pollutant loading targets and allocations for waters identified as not now in attainment with those standards. Section 303(d)(1) of the Clean Water Act provides that states, with EPA review and approval, must identify waters not meeting standards, and must establish total maximum daily loads (TMDLs) for them to restore water quality. Example Alabama 2008 TMDL Status In general, a TMDL is a quantitative assessment of water quality problems, contributing sources, and pollution reductions needed to attain water quality standards. The TMDL specifies the amount of pollution or other stressor that need to be reduced to meet water quality standards, allocates pollution control, or management responsibilities among sources in a watershed, and provides a scientific and policy basis for taking actions needed to restore a waterbody. Bays and Rivers and Lakes, Reservoirs, Estuaries Streams (Miles) and Ponds (Acres) (Square Miles) Good Waters 7, , Impaired Waters 2, , TMDL completed ,886.7 TMDL alternative 4.3 Non-pollutant impairment 22.8 TMDL needed 1, , New TMDLs completed Remaining TMDLs needed 1, , Total Assessed Waters 10, , Total Waters 77, , Percent of Waters Assessed L Only about 32% of the required TMDLs have been completed. About 13% of the rivers/streams and 88% of the lakes have been assessed. None of the coastal waters have TMDLs completed, but about 83% have been assessed.

10 Beginning in 1986, and escalating since 1996, environmental public interest organizations have filed numerous lawsuits under the Clean Water Act s citizen suit provision (section 505) alleging that the EPA had failed to carry out its mandatory duty to disapprove inadequate state section 303(d)(1) lists and/or TMDLs, or to carry out state program responsibilities where states have failed to do so. Energy Independence and Security Act of 2007 signed into Law on Dec. 19, 2007 Title IV ( Energy Savings in Building and Industry ), Subtitle C ( High Performance Federal Buildings ) Sec. 438 ( Storm Water Runoff Requirements For Federal Development Projects ): The sponsor of any development or redevelopment project involving a Federal facility with a footprint that exceeds 5,000 square feet shall use site planning, design, construction, and maintenance strategies for the property to maintain or restore, to the maximum extent technically feasible, the predevelopment hydrology of the property with regard to the temperature, rate, volume, and duration of flow. This new provision requires much more attention to controlling runoff volume, in addition to other hydrologic features. Extremes in Flows cause Infrastructure Damage and Habitat Destruction Urbanization causes extremes in flows; extended dry periods and short periods of higher flows in many areas. In the arid west, urbanization increases dry weather flows in intermittent streams due to excessive irrigation. Failing Infrastructure Photos of Coyote Creek, San Jose, CA WI DNR photos Bank instability and habitat destruction due to increased flows

11 Urban Steam Classification Sensitive 0 10% Imperviousness Impacted 11 25% Imperviousness It is possible to simplify much of the receiving water biological data to relate degradation to levels of development. Damaged % Imperviousness Channel Stability Stable Unstable Highly Unstable Aquatic Life Biodiversity Good/Excellent Fair/Good Poor Figure and Table from Center for Watershed Protection Final Effluent Guidelines to Control Discharge Pollutants from Construction Sites Published in the Federal Register on Dec. 1, Regulation is effective as of Feb. 1, After this date, all permits issued by the EPA or states must incorporate the final rule requirements. Beginning on Aug. 1, 2011, all sites that disturb 20 or acres at one time will be affected. Beginning on Feb. 2, 2014, the limitation applies to all construction sites disturbing 10 or more acres at one time. These sites must sample stormwater discharges and comply with a numeric limitation for turbidity of 280 NTU. Disturbed areas on construction sites not under active construction activities, can only remain exposed for a maximum of 14 days. Sediment Sources Not All Runoff is Sediment-Laden Birmingham Construction Site Erosion Runoff Characteristics (Nelson 1996) Low intensity rains (<0.25 in/hr) Moderate intensity rains (about 0.25 in/hr) High intensity rains (>1 in/hr) Suspended solids, mg/l 400 2,000 25,000 Particle size (median), m

12 Rainfall Energy Index for Eastern US Controls to Meet Effluent Guidelines (from the Effluent Guidelines document): Minimize the amount of soil exposed during construction activity Minimize sediment discharges from the site. The design, installation and maintenance of erosion and sediment controls must address factors such as the amount, frequency, intensity and duration of precipitation, the nature of resulting stormwater runoff, and soil characteristics, including the range of soil particle sizes expected to be present on the site Provide and maintain natural buffers around surface waters, direct stormwater to vegetated areas to increase sediment removal and maximize stormwater infiltration, unless infeasible Initial Topography (grubbing and clearing phase) Controls to Meet Effluent Guidelines (cont.): Pink: low hazard Blue: Moderate hazard Yellow: High hazard Orange: High hazard Minimize soil compaction and, unless infeasible, preserve topsoil. Soil Stabilization. Stabilization of disturbed areas must, at a minimum, be initiated immediately whenever any clearing, grading, excavating or other earth disturbing activities have permanently ceased on any portion of the site, or temporarily ceased on any portion of the site and will not resume for a period exceeding 14 calendar days Etc.

13 Soil Compaction During Site Activities General Approach The most effective way to meet the numeric effluent guidelines will be through prevention: minimize the amount of disturbed land at any one time and to rapidly stabilize any disturbed ground. Runoff controls to meet these turbidity limits in the southeast are likely limited to chemical treatment in conjunction with sediment ponds. Pitt, et al Erosion Controls Diversion Channels and Berms Erosion Controls Protect Channels (Check dams and liners)

14 Erosion Controls Slope Protection with Hydroseeding and Blankets Erosion Controls Control Site Discharges Filter fencing for small sites (but only for slope lengths less than about 100 ft). Expect about 10 to 50% control of suspended solids. Sediment ponds for areas larger than 10 acres. Expect up to 80% control of suspended solids. Measured Silt Fence Performance during Alabama Tests (about 54% reductions) Total Suspended Solids Mean + Std. Error Control Fence Nothing Lalor, et al Construction site sediment ponds can capture significant amounts of sediment, but effluent turbidity is still high.

15 Chemical Treatment of Exposed Soils These newly developed materials act by chemically combining small soil particles into larger discrete particles that are more effective in settling in ponds and in channels. Polyacrylamide (PAM) is the most common chemical being sold now. Polyacrylamide used for erosion control should have a negative (anionic) molecular charge. Passive chemical addition methods used in New Zealand to enhance sediment and turbidity control of construction site wet detention ponds. Use of Chemical-Assisted Sedimentation Example Performance Data for PAC-assisted Settling Pond Inflow Outflow SS Reduction Flow (L/sec) SS (mg/l) Flow (L/sec) SS (mg/l) Mason s Rd 3 26, Mason s Rd 2 5, OVR E 15 1, OVR E E 8 14, E 1 18, B1 Gully 0.3 4, B1 Gully , (%) Auckland Regional Council, New Zealand

16 Many examples of the applicable controls are included in: Construction Site Erosion and Sediment Controls; Planning, Design and Performance. R. Pitt, S. Clark, and D. Lake. DESTech Publications, Lancaster, PA, pages. ISBN X Table.htm Alabama Handbook for Erosion Control, Sediment Control and Stormwater Management on Construction Sites and Urban Areas. Volume 1. Alabama Soil and Water Conservation Committee, Montgomery, AL /ASWCC_June_2003_Alabama_Handbook_Constructio n_e&s_control.pdf Regulations Affecting Construction Site Erosion Control Many local and regional agencies in the US have implemented erosion control regulations for several decades (Virginia is a prime example). The 1987 Stormwater Permit Program of the National Pollutant Discharge Elimination System (NPDES) required local erosion control programs for construction sites 5 acres, or greater, for more than 10 years. Phase II of this program now requires erosion control for sites as small as 1 acre, or less. Some Features of Phase II of Stormwater Permit Program Rule became final on Dec 8, Small construction site permit applications are due, starting from March 10, Applicable to all construction sites from 1 to 5 acres (Phase I covered larger sites). Smaller sites may be covered if part of larger common plan, or if designated as a significant water pollutant contributor. Waivers Available for Small Construction Sites Low predicted rainfall erosion potential (NRCS rainfall erosivity factor, R, less than 5 for period of construction activity; not expected to be applicable for Alabama conditions), or Determination that controls are not necessary based on TMDL analysis or equivalent (considering proximity to water resources and sensitivity of receiving waters).

17 Phase II Construction Program Requirements (EPA Guidance) EPA recommends the use of existing Phase I general permits as a guide for developing Phase II small construction permits. Three general requirements: Notice of Intent (NOI) Stormwater Pollution Prevention Plan (SWPPP) Notice of Termination (NOT) Notice of Intent Contains general information (location, timing, nearby water resources, etc.) Contains certification that the activity will not impact endangered or threatened species (for the EPA s NOI, not commonly included in delegated state s NOIs) Stormwater Pollution Prevention Plan (SWPPP) Lists and describes construction site erosion controls that will minimize the discharge of pollutants from the site Technology based standards (Best Available Technology, or BAT) Professional judgment of permit writer (Best Conventional Technology, or BCT) Notice of Termination This is submitted when the final stabilization of the site has been achieved.

18 Alabama has areas that Experience some of the Highest Erosion Rates in the Nation: Rainfall energy (Alabama has the highest in the US). Soil erodibility (northern part of the state has fine grained, highly erosive soils). Site topography (many areas have steep hills undergoing development). Surface cover (prior forested cover usually totally removed during initial site grading on hilly construction sites). Common Components of Many Erosion Control Regulations 1) divert upslope water around disturbed areas, or pass it through the site along a protected channel, 2) expose disturbed areas for the shortest possible time (typically 14 day limit), either through better scheduling or by using temporary or permanent mulching or other cover, 3) treat any runoff before it leaves the site (perimeter filter fencing and downslope fencing or sediment pond, depending on size of site). Other Typically Required Erosion Control Elements: Construction wastes must be properly stored and disposed. Sediment tracking controlled using graveled driveways, roads, and construction entrances. Protect storm drain inlets. Storage piles properly located and protected from erosion. Have an effective inspection and repair program. A local construction site erosion control program would qualify and meet federal requirements of the phase 2 stormwater permit program if it met the following five principles: 1) good site planning 2) minimize soil movement 3) capture sediment 4) good housekeeping practices 5) mitigation of post construction stormwater discharges

19 and the following eight elements: 1) program description 2) coordination mechanism 3) requirements for nonstructural and structural BMPs 4) priorities for site inspections 5) education and training 6) exemption of some activities due to limited impacts 7) incentives, awards, and streamlining mechanisms 8) description of staff and resources States are already addressing these key requirements of the initially proposed Federal effluent guidelines: Stormwater Pollution Prevention Plans All 50 states require site managers to prepare a stormwater pollution prevention plan, erosion and sediment control plan, or an equivalent document. Inspections by Construction Site Operator All 50 states require construction site operators to inspect their sites on a regular basis. Erosion and Sediment Control All 50 states require site managers to implement a combination of erosion and sediment controls to prevent soil erosion and to manage construction site runoff. The EPA s proposed effluent guideline would have mandated sediment basins of a particular size across the country. Currently, states base their technical requirements for basins or other erosion control techniques on local rainfall patterns and other considerations. Stabilization of Soils After Construction All 50 states require stabilization of soils after construction activities have temporarily or permanently ceased. The EPA s proposed effluent guidelines would have mandated this step within 14 days. States currently set their own requirements based on local conditions. In dry areas, for instance, 14 days may not be necessary because of low rainfall. It may also be impractical due to slow growth of vegetation.

20 Existing Local Programs Many local governments have long standing programs in place to control sediment and erosion from construction sites within their jurisdiction. EPA s stormwater regulations (Phase I and Phase II) set minimum requirements for these programs. Approximately, 6,000 municipalities are covered by these regulations. Many of the approximately 5,000 communities covered by Phase II are just now developing or upgrading their programs to meet these requirements. Some of the minimum requirements for these local programs include: Ordinances or other regulatory mechanisms requiring the implementation of proper erosion and sediment controls Review of site plans to ensure proper design and installation of sediment and erosion controls Site inspections and enforcement of control measures Sanctions to ensure compliance Procedures for public review and comment Review of Site Plans The NPDES regulations require that municipalities set up procedures for review of site plans to ensure proper implementation of sediment and erosion controls. The EPA s proposed effluent guideline would have required certification of the design and installation of sediment and erosion controls by a qualified professional (generally a third party). States and communities are working together to define and develop effective programs. Communities have until 2008 to fully implement these requirements. The problem is lack of resources (and will) to enforce regulations, improper sizing and design of controls (let alone maintenance), and application of inappropriate controls for local conditions. This book and course are intended to help the engineer in proper application and use of erosion and sediment controls.

21 Module 1 Homework Problem Value of continuing education and engineering registration Search the internet (and/or other resources) for available continuing education classes in a technical discipline of interest to you (not necessarily construction erosion control!) Prepare a summary of the types of workshops available and how they would supplement material you have learned during your forma university education Also prepare a summary of the job opportunities available to a person having an FE and a PE license. What work activities would you not be allowed to do if you are not registered as a professional engineer.