My post yesterday, Protecting a Trench Drain talked about the difficulty of protecting trench drains. This is what can happen if you don’t protect them. These photos show sheen from oil and grease generated by construction activities around the slot drain during a rainstorm.
Phasing a Stockpile Project
Phase 1-
(A) Install silt fences on perimeter and at base of future stockpile.
(B) Clear, grub, grade, construct drainage ditches and temporary stormwater pond including outlet structure and perforated pipe level spreader drains. Grade to drain water away from outer perimeter silt fence and toward ditch.
(C) Hydroseed and install blankets in ditch line.
(D) NOTE: Background stockpile, built later, used an early generation construction stormwater treatment system and discharged to creek instead of level spreaders into vegetation.
Phase 2-
(A) Place and compact fill material to approximately 20 feet of vertical elevation.
(B) Trackwalk and hydroseed slope.
Phase 3-
(A) Same as Phase 2.
(B) Same as Phase 2.
Phase 4-
(A) Place and compact fill material to approximately 20 feet of vertical elevation. Start base of slope 15 feet in from lower fill and grade to drain away from lower slope and to the stormwater pond.
(B) Trackwalk and hydroseed slope.
(C) No hydroseed on top of the pile as material is continually brought in as available.
Thousands of gallons of clean rainwater draining off the roof deck onto bare soil turning into thousands of gallons of water that’s too dirty to discharge without treatment. With pre-planning, a temporary collection system could have been developed and installed to contain, collect and convey the clean water to an existing drainage system. Without such a system, the dirty water had to be treated chemically to reduce the turbidity enough to discharge to the storm system.
Questions to ask: Is this an existing manhole? If it is, is it connected to the storm system? Is this a new manhole? Is it connected? Is everything grouted? Since this is below existing, bare grade, any water that drains to this manhole will be very dirty. If the system is live, and the manhole is not grouted, all of the dirty water will end up somewhere it shouldn’t.
Pipe slope drains are a great best management practice for conveying water down to the base of a slope. Water allowed to flow over a slope will cause rills and gullies to form, depositing tons of sediment at the bottom of the slope. This clip shows a good application of a pipe slope drain, except the pipe doesn’t go to the base of the slope.
Construction Site Stormwater Runoff Control
Poorly maintained BMPs can result in significant quantities of sediment being discharged to storm drains. Uncontrolled storm water runoff from construction sites can significantly impact rivers, lakes and estuaries. Sediment in water bodies from construction sites can reduce the amount of sunlight reaching aquatic plants, clog fish gills, smother aquatic habitat and spawning areas, and impede navigation.
Phase II MS4s are required to develop a program to reduce pollutants in stormwater runoff to the MS4 for construction sites disturbing one or more acres. This primarily includes developing:
An ordinance,
Requirements to implement erosion and sediment control best managment practices (BMPs),
Requirements to control other waste at the construction site,
Procedures for reviewing construction site plans,
Procedures to receive and consider information submitted by the public, and
Procedures for inspections and enforcement of stormwater requirements at construction sites.
In addition to the stormwater requirements that Phase II MS4s place on construction sites, construction operators must also apply for NPDES permit coverage if their project disturbs at least one acre and discharges to a waterbody.
A description of these requirements is available at EPA’s stormwater construction website.
Temporary construction erosion and sediment control means managing storm water until the permanent storm system is operational and the site has been stabilized with vegetation, concrete, asphalt, landscaping and other practices. This shows how to inspect a temporary drainage system.
If I’ve said it once, I must have said it 3 or 4 times: “Keep your tires clean!”. Who wants to use a tire wash and have to get rid of a whole lot of dirty water (process water) that can’t go down the storm drain? Save yourself some hassle and money. Give your employees a raise with the money you save. Make sure your trucks are loaded when on asphalt.
Catch Basin Open to the Rain – When inspecting a project, I always look closely at the storm drain system to verify whether any dirty water from the project will drain to an active system. In this example, the catch basin has been installed but the main line it is connected to is not active.
Low Impact Development for Public Works Construction:
Erosion and Sediment Control Compliance
David S. Jenkins, Seattle, Washington
Introduction
Construction is a messy business; in the Puget Sound region of western Washington, with average annual rainfall of 40″ to 60″, it can also be challenging. Uncontrolled erosion from a construction site can generate 10-1000 times the quantity of sediment that occurs naturally from vegetated areas. Most construction in western Washington occurs near wetlands, streams, lakes, or the Puget Sound where sediment loss can reduce beneficial uses, or worse, destroy a salmon stream.
This paper will discuss proven methods that public works professionals can utilise to improve erosion control compliance and reduce project impacts.
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