Script for Module 2: What is a SWPPP



Script for Module 3: Typical Roadway Drainage

Slide 1: This module looks at the Good Housekeeping requirements for some of the physical components of what we think of as a traditional or typical stormwater system. The focus will be on where stormwater enters the MS4 system, and where it leaves the system. (MS4 – Municipal Separate Storm Sewer System)

Slide 2: As we noted in the BMP (Best Management Practices) module, at this point in time most of our systems send runoff directly to a water body, be it wetland, pond, stream or estuary. So it’s very important that we keep them in a condition where they can trap sediments and other pollutants.

Slide 3: We’ll review the Good Housekeeping goals related to catch basins, shoulders & ditches, and outfalls.

Slide 4: As we did in the last module, we’ll read each Good Housekeeping Goal as it’s written in the General Permit. Then we’ll review some background that may help clarify or expand on the intent of the goal. Next will be a discussion on what our MS4 does to meet that goal, and how we report progress. If you come up with ideas on how to improve the way we do things, please write them down on the sticky notes and stick them on the flip chart.

Slide 5: We’ll start with the catch basin program. Catch basin and manhole sumps are the major devices in “traditional” systems for trapping sediment.

Slide 6: Hold on, because this is a long goal. The Permit requires “procedures for implementation of a regular catch basin inspection and cleaning program to inspect all catch basins annually commencing by the third year of the program, document the results of the inspection, and clean structures as necessary. The operator may request approval for a lesser frequency of inspection based on at least two consecutive years of operational data indicating the system does not require annual cleaning. Documentation supporting a different frequency of catch basin cleaning may be based on observations made on sediment accumulation in catch basins, sediment accumulation at outfalls or observed flooding problems. The operator must submit this documentation and supporting rationale to the Department with the Annual Report required in this permit. The program must also include procedures to increase the inspections and cleaning based on field investigations, complaints and areas that are prone to sediment accumulation. Changes to the frequency of catch basin cleaning must be made when field observations reveal that the chosen frequency is not being effective. The program must also include the inspection and cleaning of other elements in the system, such as manholes, when catch basins in the system are found to be overfilled or failing. Describe coordination of inspection of catch basins for maintenance and inspection for illicit discharge detection and when recording additional elements of the MS4.” The goal goes on to provide special direction to RIDOT.

Note to RIDOT trainer: Include the remaining section of IV.B.6.b.iii. on page 24 of the General Permit. This text is as follows:

“The RIDOT must apply this program to the MS4 within the urbanized and densely populated areas but may propose an alternate program for the MS4 that serves divided highways outside the urbanized and densely populated areas or if the divided highway is inside the urbanized or densely populated area, the RIDOT can provide justification that road sanding is the only potential significant source of sediment accumulation and the MS4 is not physically-interconnected with another MS4 or receive discharges from other properties.”

Slide 7: That’s a lot of words for what can be a fairly simple, routine practice, so let’s take it a bit at a time. First, note that the program should start by inspecting all catch basins, at least for the first two years. That implies that we know where all the catch basins are.

Slide 8: This is a point where the Good Housekeeping program is coordinated with the Illicit Discharge program; you may recall it is another one of those six Minimum Measures of the SWMPP (Stormwater Management Program Plan).

Slide 9: Requirements under Illicit Discharge include recording the location of outfalls, along with catch basins, manholes and pipes in the system on an on-going basis; at a minimum noted on plat maps. This mapping project went one step further, and also delineated the catchment, or area that drains to this particular system.

Note to trainer: You can also discuss your municipal maps of the stormwater drainage system here, instead of in slide 12, if you chose.

Slide 10: After 2 years, we should have enough information to consider changing the frequency of inspections. Under RI General Law 45-61.1, the MS4 has to designate those storm drain systems that are prone to flooding or contribute significantly to storm water management problems. Catch basins in those systems must be inspected at least once a year; we’ll do it more frequently if our records show the need. We may be able to reduce the frequency for non-flood-prone catchbasins, IF WE HAVE THE RECORDS TO SHOW that there is not enough sediment in the system to require annual maintenance.

Catch basins are meant to remove runoff from the road surface. Catch basin sumps are meant to trap pollutants, particularly sediments. They are most effective when in good condition and less than 60% full. We can be most effective if we document their condition and use that information to schedule maintenance where and when it is most needed.

Slide 11: Another part of the goal is to maintain as necessary. Maintenance needs are determined and scheduled based on the inspection. Trash and debris are removed, sediment is cleaned out with a clamshell or vac truck, broken grates are replaced, and so on. And records are kept so we can compile our Annual Report to RIDEM, and so we can focus the inspection and cleaning programs to where they are most needed.

Slide 12: (Talk about your catch basin program: where the maps are, how flood prone areas are designated, inspection and maintenance forms, who maintains the inspection schedule, what is looked at during inspection, how inspections are translated into work orders for maintenance, what to do when illicit connections, biohazards or petroleum products are found, safety procedures, cleaning procedures, how volumes are estimated, how field records are used).

Note: RIDOT’s Inspection & Maintenance Checklist is in the workshop material. The forms are located: \Resources\RIDOTDatabase\RIDOT_BMP_Inspection_Forms.xls

Slide 13: Before you head out to the field to inspect catch basins, it is recommended that you make sure you have all these materials with you: maps so you know where the catch basins are, a camera to record anything unusual, a supply of forms to fill out as you inspect or clean, something to write with, a probe to help determine depths, something to lift grates or manholes, and a cellphone.

Slide 14: Our inspections should be more than a quick look to see if the catch basin needs cleaning or repair. The Illicit Discharge Minimum Measure requires an inspection of manholes and catch basins for illicit connections and non-stormwater discharges. If found, those need to be reported so followup procedures can be undertaken.

Note: The Neighborhood door-hanger found in the workshop materials can be used to notify residents of illicit discharges in their area. Door hanger is located: \Module3_Final\Resources\DoorHanger

Slide 15: We need to estimate volumes, to improve our schedules and back up funding requests. Volumes can be estimated in the office if depths are measured in the field, as long as we also have sump area and/or pipe size. With a known or assumed total sump depth, we only need to measure from the invert of the lowest pipe to the top of the sediment, then subtract. If you’re cleaning at the same time you’re inspecting, a quick rule of thumb is to clean the catch basin if the top of sediment is less than 2 pipe diameters down.

Slide 16: I wanted to talk briefly about infiltrating catch basins, or dry wells. They usually sit alone, disconnected from a drainage system, and could almost be considered structural BMPs, because they are intended to introduce stormwater into the ground.

These structures should be inspected about 72 hours after a significant rain. If they still have water in them, the bottom needs to be scarified to increase infiltration. Does anyone have any suggestions on a tool to help break up the bottom?

Note to trainer: Solicit responses from staff on what equipment might be used to scarify the bottom in a confined space (e.g. small backhoe).

Slide 17: And a quick reminder to be safe out there; you’ll be working at the edge of the road.

Slide 18: Other opportunities for capturing pollutants in the drainage system are along the shoulders and in the roadside ditches or swales. We will see these play a larger role in our storm water systems as Low Impact Development (LID) techniques are adopted.

Note to trainer: It is recommended that you pause here for questions or comments on catch basins.

Slide 19: To be in compliance with our General Permit, we need to have “Procedures to minimize erosion of road shoulders and roadside ditches by requiring stabilization of those areas. Some recommended methods for stabilization may include rip rap, or gravel, to reduce the velocity of the storm water runoff, or planting of grass, shrubs or trees.”

Slide 20: This slide reminds us of a couple things about shoulders: 1) they can contribute runoff TO the road as well as accepting it FROM the road, depending on topography, and 2) they will most likely not be accepting water from the road if there’s a curb. A curb automatically concentrates flow, usually directing it to a catch basin.

Slide 21: One of the first stormwater standards of LID is to get rid of the curbs and spread the flow through a well-vegetated shoulder, to slow runoff and encourage infiltration.

Slide 22: Erosion at the interface of road and shoulder can lead to the same type of channeling as a curb does. Road sand build-up can also reduce the effectiveness of the shoulder in getting storm water off the road surface.

Ideally, shoulders should meet flush with the driving surface, and slope slightly away – at ½ to ¾ inch per foot.

Slide 23: A well-vegetated, smooth-shaped shoulder can act as a filter strip, allowing sheet flow from the road to slow, drop sediments, and perhaps infiltrate. Routes 1 and 4 in South County have some excellent examples of well-maintained shoulders and swales.

Slide 24: Way back when, the old Soil Conservation Service used the term “ditch” when describing a practice whose main function was to remove ground water. If you wanted to remove storm water, you installed a waterway – either grassed or rock-lined.

But for the Good Housekeeping Measure, any channel that carries a concentrated flow, but that isn’t on the list of BMPs, should be considered a “ditch” and included in the maintenance schedule.

Slide 25: Channels carrying concentrated flows should be designed to have sufficient capacity to carry that flow (using a 10-year storm at minimum). The grade of the channel will influence its shape and the need for stone, because grass will not hold the soil under high velocities (3.5 feet per second maximum). Grade also influences the ability of the channel to treat storm water; the flatter the grade the more opportunity for solids to settle out and infiltration to occur.

Slide 26: As we look for opportunities to implement LID practices, we’ll see “ditches” become more and more elaborate. They’ll have names like “rain garden” or “biofilter”, and may have site-specific O&M (Operations and Maintenance) plans. In that case, they’ll move to the list of structural BMPs.

Slide 27: (Talk about your program of maintaining shoulders & ditches: maintenance forms, how your MS4 identifies/locates, what is in your database, how you establish priorities for maintenance, safety procedures, typical steps, how potential illicit discharge or biohazards are handled, how information from the forms is used in the Annual Report and in determining need for major repairs or retrofits.

Note: RIDOT’s Inspection & Maintenance Checklist is in the workshop packet. Document is located: \Resources\RIDOTDatabase\RIDOT_BMP_Inspection_Forms.xls

Slide 28: Safety tips for shoulders and ditches are fairly similar to those for catch basins.

Slide 29: Among the suggestions from other states is to create a map of potential problem areas, and inspect them after heavy rains.

Slide 30: For shoulders, scour areas should be refilled and compacted, and seeded as necessary. If scouring continues, it may indicate concentrated flow, requiring an asphalt or rock-lined chute. Vehicle pull-offs may require gravel, or fencing.

Road sand will build up the shoulders, perhaps to the point where storm water can no longer run off the road. Once the shoulder builds up so it’s 3” or more higher than the road, it’s time to knock it back down, reseed and mulch.

Slide 31: Vegetation for shoulders and, to some extent, ditches should be salt-tolerant, require little fertilization, and be fairly short to reduce the need for mowing.

Slide 32: Unfortunately, we do have to contend with some invasive species, especially in the wet pockets of ditches. Cleaning these areas out will require special treatment of the spoil to prevent the spread of the invasives.

Slide 33: Which brings us to ditch maintenance. As an area of concentrated flow, a ditch is subject to RI’s Freshwater Wetlands Regulations, so we need to plan our maintenance activities in advance. We’ll schedule cleanout only in the driest times of the year. The recommended procedures include starting at the outlet end, going up only a short stretch, then either waiting for that to stabilize before doing the next stretch, or divide the length of the ditch into short sections and only disturb every other section in a given year.

Slide 34: We need to maintain the capacity of the ditch and minimize re-suspension by removing sediment once it builds up to 3” deep. We should be checking sediment depth at least every 5 years or so, depending on the channel grade and the amount of sand applied in the drainage area. If we expect infiltration through the bottom, we’ll need to maintain a friable surface by discing or rototilling – again in short sections at a time.

Slide 35: Finish up each day by seeding and mulching, in case it rains overnight. Once the change in grade of the exposed channel exceeds 2 feet, install a temporary check dam. For example, if the channel is on a 2% slope, put in a check dam every 100 feet. The check dam in the image is of stone, and they are adding compost to help filter finer particles. If the bottom continues to scour, it’s time to go back to the drawing board, to design an armored channel.

Slide 36: Keep your eyes and nose open when you’re out on the road. If you smell something unusual, or you see a strange color or oily sheen, report it immediately. And keep an eye out for any impacts on the integrity of the shoulder or ditch when changes are made in the area: increased runoff, concentrated flow or higher velocities can take them out of equilibrium.

Slide 37: Outfalls provide our last chance to reduce the impact of our storm drain system on the waters of the State.

Note to trainer: It is recommended that you pause here for questions or comments on shoulders & ditches.

Slide 38: According to the General Permit, we need to have “Procedures to identify and report annually as part of the annual report submitted to the Department in accordance with Part IV.G.2.e. known discharges causing scouring at outfall pipes or outfalls with excessive sedimentation for the Department to determine on a case-by-case basis if the scouring or sedimentation is a significant and continuous source of sediments. The operator of the MS4 must include procedures to remediate scouring or sedimentation upon written notification by the Department. Some recommended methods of remediation may include the repositioning or extension of outfalls and the addition of rip rap.”

Slide 39: Here’s another point where the Good Housekeeping program is coordinated with the Illicit Discharge program. We inspect outfalls two times a year under the Illicit Discharge Minimum Measure. As part of that inspection, scouring and sedimentation should be noted.

Slide 40: We report the condition of those outfalls under the Good Housekeeping Minimum Measure in our Annual Report to RIDEM. Because outfalls have the potential to directly impact State waters, and because permits will be required, we don’t begin major repairs until notified by the State.

Slide 41: Not that we should ignore a problem until RIDEM steps in, especially in cases of excessive sedimentation. Something like this is an indicator of problems in the system above the outfall: catch basin sumps are probably full, perhaps a construction site needs some enforcement action.

Slide 42: Especially in tidal waters, we want to make careful note of whether we think the sediment seems to be coming out of the pipe, or is being carried into the pipe by the receiving waters. We have more ability to control what’s coming through our system.

Slide 43: Scouring may be caused by concentrated flow coming downslope near the pipe, again an “uphill” problem which we may be able to address by redirecting flows. In this particular slide the stream channel also appears to be cutting into the bank, and I’m sure the tree is doing wonders for the physical integrity of the pipe and headwall!

Slide 44: (Talk about your program of inspecting and maintaining outfalls: who does inspections, how they are documented, how problems are reported to RIDEM and maintenance staff, how maintenance schedule is compiled, typical access and/or equipment issues they should expect)

Slide 45: In general, outlet protection will be needed anytime the velocity of water leaving the pipe is greater than 2.5 feet per second. The size of the apron and stone is determined based on size of the pipe, flow and tailwater. A stilling basin should help trap sediments where they can easily be removed.

Slide 46: If an outfall ends at the top of a bank, chances of there being a scouring problem are roughly 100%. Half-culvert chutes have been used in the past, but there may be problems in providing the support needed to keep them in place on a steep slope. Flexible pipe conforms better to the slope, and should require only some stakes to keep it in place.

Slide 47: Sediment removal can be tricky, due to the sensitivity of the area and accessibility, not to mention you’ll often be dealing with saturated soils. There may be a lot of hand shoveling involved, plus dragging the spoil material back up hill. Like ditch cleanings, these sediments may have rhizomes or seed from invasive species mixed in, so they’ll need special treatment.

RIDEM wetland regulations indicate that as long as you are maintaining a structural BMP that you DO NOT need a permit from RIDEM. This comes from Rules 6.03D and 6.03L of the Rules and Regulations Governing the Administration and Enforcement of the Fresh Water Wetlands Act. (Rule 6.00 – Exempt Activities). RIDEM wetland regulations indicate that as long as you are maintaining a structural BMP that you DO NOT need a permit from RIDEM. This comes from Rules 6.03D and 6.03L of the Rules and Regulations Governing the Administration and Enforcement of the Fresh Water Wetlands Act. (Rule 6.00 – Exempt Activities). Be sure to review section 6.01 “General Conditions for Exempt Activities” for more information on any specific things you must do while working in the wetland on these exempt activities.

CRMC notes that BMP maintenance usually falls under the assent for a development / redevelopment project, and is allowed for the life of the BMP.  A BMP maintenance schedule is usually submitted as part of the project application, though if the maintenance schedule isn’t followed, this does not negate permission for future maintenance.  If there is no associated project permit, apply for a permit; CRMC generally treats these types of applications as “administratively approved as having no significant impact”.

Slide 48: And remind those who are looking at retrofitting outfalls (to provide more pollutant attenuation) to design for ease of maintenance!

Slide 49: For 300 years or so, we’ve been building and maintaining a system for getting water out of the way of our travel path. It is only fairly recently that we’ve started to recognize how serious the impact of our activities is. Now we know, and it’s comforting to know that some of what we’ve been doing all along has helped to clean our water. We just have to do more of it, more often, with a few tweaks, and keep our eyes peeled for problems.

Slide 50: Thanks for your attention. Shall we see what we have or want to add to the flipchart, in terms of suggestions for improving our current procedures?

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