Inspection and Maintenance of Stormwater Control Measures: Helping Protect Greensboro s s Water Quality and Water-Supply

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1 Inspection and Maintenance of Stormwater Control Measures: Helping Protect Greensboro s s Water Quality and Water-Supply NC APWA Stormwater Management Conference-September 16, 2013

2 Program Background Privately owned stormwater treatment devices (SCMs)) are required throughout Greensboro s jurisdictional limit due to either watershed water- supply and/or Phase II regulations. Watershed regulations began in mid 1980 s. Formal inspection program didn t t begin until Most of the SCMs had not been maintained since originally installed. A significant educational effort along with persistent inspection and enforcement was necessary to complete first full round of inspections and necessary maintenance.

3 Program Background The City of Greensboro's water-supply watershed and stormwater management ordinances (Ch. 30) require property owner(s) ) to meet certain maintenance requirements for constructed SCMs. Since 1998, Stormwater Management Division staff have been conducting these inspections to ensure privately owned SCMs are being maintained and functioning properly. The City of Greensboro currently inspects approximately 600 SCMs! Properly designed, built, and maintained SCMs should ideally be an asset to a property, not a liability Right?

4 Asset or liability to property owner?

5 SCM Locations in Greensboro

6 Local Permit Issuance Group Development, Commercial, & Subdivision Plans are reviewed by City s s Technical Review Committee (TRC). Stormwater Engineer reviews to make sure plan meets Post construction SWM & LDO requirements. Issuance of building or grading permit contingent on TRC approval. After plan approval by TRC, a pre-construction meeting is set by the Engineering & Inspections Department

7 Local Permit Issuance Design engineers are involved during construction phase with City performing site inspections. Final inspection of SCM performed by Stormwater Operations Section. Design Engineer submits final certification and as- builts. City inspects and accepts SCM once standards are met. Then proceeds with plating and CO issuance. Ownership of SCM transfers to HOA or property owner Maintenance Inspections Start!!!!

8 Where to start first? Establish inspection process for efficient identification of any problems that may affect the safety or functional efficiency of the SCMs. 1. Development of inspection and documentation procedures Dam Safety Inlets and Outlets Vegetation Sedimentation 2. Database to manage inspection history 3. Enforcement procedures

9 Development of inspection and documentation procedures

10 SCM Inspection Process 1. Research and investigate ownership information. Contact information, especially for HOA s,, tends to change often. 2. Complete onsite inspection and fill out inspection form. 3. Mail copy of inspection form to owner(s). If maintenance is needed, allow 90 days to complete maintenance. 4. If work not complete in 90 days, allow an additional 30 days to complete maintenance. 5. If work not complete in 120 days, City may complete the maintenance and assess the owner(s) ) for costs and damages incurred!

11 SCM Inspection Program Work Flow Chart Education letter sent Attachment #1 (only if ownership has changed) Inspection list created Supervisor receives inspection list Ownership and site plan research On-site inspection Phone call to inform current owner of annual inspecition (if ownership has NOT changed) Follow up phone calls Are recommended/required items complete?? Re-inspection Follow-up phone calls and technical assistance throughout 90 days January 2007 T W T S M F S days Inspection report sent - If no action needed, send regular mail & close out - If recommended items, send regular mail - If required items, send certified mail along with formal letter, attachment #3 January 2007 send certified NOV S M T W T F S (and coordinate with Supervisor) days send 2nd certified NOV (and coordinate with Supervisor) final letter & close out (if required items complete or if recommended items complete or uncomplete) If required items NOT complete Supervisor and Managers SEEK ASSISTANCE & pursue enforcement January 2007 T W T S M F S days

12 Development of standardized inspection checklists

13 What do we inspect, and what problems do we look for?

14 Dam Safety Leakage and Seepage Inspect downstream side of earthen dam for evidence of significant leakage or seepage (saturated soil, sediment deposits, flowing water, etc). Inspect backside of reinforced concrete dam for cracks, leaks, or displacement (noticeable leaning or bulging). If evidence is observed, owner should seek assistance from a professional engineer.

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16 Dam Safety Dam material problems On earthen dam, look for evidence of pronounced cracks on the embankment surface. Perpendicular cracks may indicate differential settling of the dam. Parallel cracks may be due to improper compaction or shrinkage of the clay. Depressions, sink holes, or animal burrows. If evidence is observed, owner should seek assistance from a professional engineer.

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19 Dam Safety Vegetative growth This is one of the most common problems we see! The earthen dam should be well-vegetated, but grass should be maintained at a height of less than 9. 9 Trees, saplings, and other woody vegetation are not permitted on any part of the earthen dam. Large roots systems can jeopardize the integrity of the dam and provide pathways for seepage. Thick, tall vegetation (Lespedeza( Lespedeza,, briars, etc.) can also provide cover and hide the activity of burrowing animals (muskrats and groundhogs). The network of burrows can weaken the dam and also provide pathways for seepage and future dam failure.

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23 General Erosion The dam, side slopes, inlet and outlet areas, as well as localized watershed draining to the pond should remain vegetated and stable in order to prevent erosion and excessive sedimentation.

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26 Maintain or enforce S&EC measures within drainage area Periodic sweeping of streets and parking lots can also reduce amount of sediment and other debris entering the pond.

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28 Embankments Pond embankments should be kept well- vegetated to prevent erosion. Grass on the pond embankments should be well maintained (mowed at least once a year). Small channels and gullies should be filled, compacted, and seeded. Landscaped trees, shrubs, and flowers are acceptable on embankment areas (no trees on the earthen dam!).

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32 Inlet and Outlet Pipe Areas Structural integrity of inlet and outlet structures should be intact and functional. Inlet and outlet pipe areas should remain clear of obstructions (sediment build-up, up, trash, and debris) and overgrown vegetation. Gullies or eroded areas should be repaired with compacted soil, geotextile fabric, and rip-rap. rap. Maintain access to the outlet pipe, and discharge area should be inspected to make sure it is not piping.

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35 Water Quality/Low Flow Orifice The water quality/low flow orifice in the metal riser or concrete spillway should be protected with a trash guard. The orifice should be routinely inspected to make sure it is not clogged (sticks, bottle caps, plastic bags, fish, frogs, algae, etc).

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37 Trash Rack The trash rack on top of the metal riser is intended to trap sticks, trash, and other debris during high-flow events. Like the orifice, the trash rack should be routinely inspected to make sure it is clear of debris.

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41 Emergency Spillway Normally constructed as a depression or notch in the earthen dam or in the corner of the dam area. Typically lined with rip-rap. rap. The emergency spillway should be maintained just like the earthen dam no woody vegetation, and grass should be well maintained (mowed at least annually). In the event that the emergency spillway is utilized (e.g. during a hurricane), spillway must not be blocked or impeded!

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44 Sediment Accumulation Removal of built-up up sediment is eventually going to be necessary for every detention pond. START BUDGETING FOR IT NOW!!!! Maintain clear access easements to the pond. Set aside an onsite disposal area for dredge material. Land application is allowed and saves on hauling and disposal costs. Routinely inspect sediment levels in pond, make observations of sediment plumes, and compare to allowable sediment storage per engineering design plans.

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50 Other General Maintenance Routine trash pick-up in and around pond. Stock pond with Gambusia (mosquitofish). County Division of Environmental Health may assist. Manage sediment level and vegetation within pond or SCM. Excessive vegetation has been shown to provide cover and habitat for mosquito populations. Fencing around the pond is solely up to the pond owner(s). City of Greensboro does not require fencing.

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54 Gambusia (mosquitofish) The mosquitofish only grows to about 1.5 long, and can survive in hot, stagnant, low-oxygen oxygen water (like a detention pond). They are voracious eaters, but feed primarily on mosquito larvae ae and pupa in the water column.

55 What do we do with all the information? Store ownership and inspection history in both hard copy and a database format. Document Document Document

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59 Document everything in a hard copy file folder for each facility. Include all letters, pictures, any conversations, voice mails, or s. Should case ever proceed to enforcement, a detailed history of the City s effort to date is invaluable! TELEPHONE CALL LOG Call To: Call From: Date: Time: Comments:

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62 Enforcement Procedures 1. Was maintenance required or recommended? 2. When required work hasn t been completed within 90 day timeframe 1 st NOV is issued giving an additional 30 days to complete the required work. 3. If required work still not completed by the additional 30 day deadline, 2 nd and final NOV is written stating that the City (or our contractor) can come in at any time and complete the work and bill the property owner. Note: NOVs are standardized template letters.

63 Bioretention Areas Other SCM types: Sand Filters Approved Proprietary Devices Stormwater Wetlands

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68 Take home lessons: 1. Thorough and consistent maintenance inspections are the key to having SCMs maintained by private property owners. 2. Well maintained SCMs will protect water quality. 3. Poorly maintained SCMs will not protect water quality and will become a problem for the property owner. 4. Owner education is an essential and necessary component for the owner to understand the significance of these structures and how to take care of them. 5. It takes more persistence than originally thought to convince people to spend money on SCM maintenance. The City feels that in-house inspections of SCM s ensure maintenance is being done and wq is protected.

69 Question or Comments? (336)