Attachment_C_EOC_Stormwater_System_BMP_(2).pdf

EOC Stormwater Management System BMP

Gainesville Regional Utilities

Eastside Operations Center

Best Management Practices for

Stormwater Control System Inspection, Operation and

Maintenance

Prepared by:

Innovative Waste Consulting Services, LLC

6628 NW 9th Blvd, Ste. 3

Gainesville, Florida 32605

November 2017 williamska Typewritten Text williamska Typewritten Text williamska Typewritten Text williamska Typewritten Text

ATTACHMENT "C"

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Table of Contents

1 Introduction

1.1 Statement of Purpose

1.2 Stormwater System Design

1.2.1 Collection and Conveyance

1.2.2 Stormwater Ponds and Wetlands

1.3 Document Version

2 Personnel

2.1 Utilities Facilities Manager

2.2 Water Distribution Supervisor

2.3 Utilities Facilities Lead

2.4 Utilities Facilities Technicians

3 Inspections

3.1 Monthly Inspection Guidance

3.1.1 Collection and Conveyance Infrastructure

3.1.2 Wet Detention Ponds

3.1.3 Pond 600

3.1.4 Wetlands

3.1.5 Material Storage Bays

3.2 Post-Storm Inspection Guidance

3.2.1 RCP Obstructions

3.2.2 Pond 600

4 Pond Bottom Surveys

5 System Operation and Maintenance

5.1 Preventative Maintenance

5.1.1 Vegetation Management

5.1.2 Aerators

5.1.3 Pond 600

5.2 Corrective Maintenance

5.2.1 Infrastructure Damage or Obstruction

5.2.2 Bank Erosion

5.2.3 Algae Blooms

5.2.4 Pond Turbidity

5.2.5 Pond Sediment Accumulation

5.2.6 Pond 600

5.3 Aesthetic Maintenance

5.3.1 Litter Removal

5.3.2 Landscaping

5.3.3 Nuisance Vegetation

5.4 Summary of Routine Maintenance Activities

6 Spills and Additional Concerns

6.1 Spills

6.2 Site Construction

6.3 Onsite Material Storage Piles and Equipment Cleaning

6.4 Dumpsters

7 Record Keeping

8 References

List of Figures

Figure 1-1. Typical Stormwater Curb (A) and Grated (B) Inlets

Figure 1-2. Mitered End Section with Riprap Armor

Figure 1-3. Site Stormwater Ponds, Wetlands and Flow Paths

Figure 2-1. EOC Stormwater Control System Inspection and Maintenance Responsibility Hierarchy

Figure 3-1. Flattop Riser Flow Control Features

List of Tables

Table 5-1. Summary of Stormwater Control System Routine Maintenance Activities

List of Appendices

Appendix A Stormwater System Monthly Inspection Form

Appendix B Post-Storm Inspection Form

Appendix C Storm Drain Location Areas

Appendix D Location of Pond and Wetland Stormwater Control System Infrastructure

Appendix E Aerator Maintenance Instructions

Appendix F Stormwater Management, Grading and Drainage for GRU Eastside Operations

(Bentley, 2010a)

Appendix G Landscape Ordinance Plan (MDG, 2010)

Appendix H Exceptions Report - Operation and Maintenance Inspection Certification

Appendix I Florida-Friendly Plants for Stormwater Pond Shorelines (UF IFAS, 2013)

Appendix J Aerial Image of Storm Drain Inlets and Building 3 Parking Lot Area Maintained by

Water Distribution Unit

List of Acronyms, Abbreviations, and Initialisms

ADS Advanced Drainage Systems

BMP Best Management Practices Guidance Document

CFR Code of Federal Regulations

EOC Eastside Operations Center

FDER Florida Department of Environmental Regulation

FSM Flowers Surveying and Mapping, Inc.

GRU Gainesville Regional Utilities

Lead Utilities Facilities Lead

Manager Utilities Facilities Manager

MDG McClain Design Group, Inc.

NOAA National Oceanic and Atmospheric Administration

NTU Nephelometric Turbidity Units

OSHA Occupational Safety and Health Administration

PVC Polyvinyl Chloride

RCP Reinforced Concrete Pipe

SJRWMD or District St. Johns River Water Management District

SPCC Spill Prevention Control and Countermeasure

Supervisor Water Distribution Unit Supervisor

Technician Utilities Facilities Technician

UF IFAS University of Florida Institute of Food and Agricultural Sciences

US EPA United States Environmental Protection Agency

1 Introduction

1.1 Statement of Purpose

This best management practices guidance document (BMP) was developed to assist Gainesville Regional

Utilities (GRU) in the inspection, operation and maintenance of the stormwater control system at the

Eastside Operations Center (EOC) in accordance with Permit No. 4-001-15619-3 issued by the St. Johns

River Water Management District (herein referred to as SJRWMD or District) and the current body of standard operating procedures for stormwater control known as best management practices. Condition

24 of the site’s permit (SJRWMD, 2010a) required the inspection of the system within 2 years of construction completion and requires additional inspections every two years thereafter (minimum).

1.2 Stormwater System Design

The EOC property is comprised of 118.6 acres and has an assortment of onsite buildings used by several

GRU departments. As part of an environmental resource permit issued by SJRWMD (2010a), GRU was authorized to construct a surface water management system per the design and plans developed by

Bentley Architects and Engineers (2010a, 2010b). It appears that construction of the stormwater control system was completed in mid-2011 based on an as-built survey completed in August 2011 (FSM, 2011).

An overview of the design of the stormwater control system is provided in a calculation report and a design drawing set prepared by Bentley Architects and Engineers, last revised 16 February 2010. The system includes a series of stormwater drains located on paved and unpaved surfaces of the site that collect and route stormwater by means of reinforced concrete pipes (RCP) to wet detention ponds (i.e., Ponds 100, 301, 300, 402, 400), a dry retention pond (i.e., Pond 401) and a dry retention basin (i.e., Pond

600) (Bentley, 2010a; SJRWMD, 2010a).

Several of these ponds allow the controlled release of stormwater to wetlands located around the site that generally drain eastward to Little Hatchet Creek or westward to Hogtown Creek by way of Springstead

Creek (SJRWMD, 2010a).

1.2.1 Collection and Conveyance

Fifty (50) stormwater drains are scattered around the site, including 44 grated inlets and 6 curb inlets;

please see Figure 1-1 for the most common types of stormwater drains used at the site.

Figure 1-1. Typical Stormwater Curb (A) and Grated (B) Inlets

Site grated inlets are located on both paved and unpaved (i.e., grass) surfaces. Once stormwater enters the drains, it is routed to the ponds by a series of RCPs, ranging from 15 to 48 inches in diameter. The termination point of each RCP is a mitered end section, which discharges the stormwater over a riprap-armored slope. Please see Figure 1-2 for an image of a mitered end section.

Figure 1-2. Mitered End Section with Riprap Armor

1.2.2 Stormwater Ponds and Wetlands

When sufficiently filled, the 7 stormwater ponds located at the site drain to 5 wetland areas. Several ponds are connected to each other by RCPs which terminate as concrete headwalls; ponds 300 and 301, and ponds 402 and 400 are paired in this manner. Dry retention pond 401 is connected to Pond 400 through a grated inlet located at the bottom of Pond 401. Figure 1-3 presents an aerial image of the site which shows the location of stormwater ponds, wetlands, and stormwater flow paths between these features

(shown as yellow arrows). Please note that, for clarity, this figure does not show stormwater drainage paths from surface drains (e.g., curb inlets, grated inlets). It should be noted that each flow path shown in the figure is associated with a stormwater conveyance infrastructure component (e.g., an RCP).

Figure 1-3. Site Stormwater Ponds, Wetlands and Flow Paths

Several of the wet detention ponds (i.e., Ponds 301, 300, 402, 400) were constructed with aerators to keep the water in the ponds oxygenated and thereby prevent anaerobic conditions from developing

(Bentley, 2010b). The aerator system at each pond includes 1-2 air compressor cabinets located on the pond bank which are connected (by buried air lines) to diffuser heads located at the deepest part of each pond.

1.2.2.1 Pond 600

Pond 600 was designed as a dry retention basin; a system of perforated, 6-inch, ADS underdrain pipes underlay the bottom surface of the basin which is designed to allow the drainage of approximately

316,000 gallons over 36 hours (Bentley, 2010b). The underdrain pipes are located approximately 2 feet below the pond bottom surface and are accessible by cleanouts located on either end of each underdrain.

The cleanouts terminate at the surface as concrete collars with metal lids. Individual underdrains are connected to 8-inch manifold pipes, which combine and terminate as a single 8-inch pipe near the base of a flattop riser (i.e., S620); this flattop riser is one of the two drainage points for the basin. The other drainage point is a riprap-armored overland weir, which is designed to allow the controlled release of stormwater during very high-water level conditions.

Unlike the other ponds at the site, the mitered end section stormwater inflow locations of Pond 600 were constructed with forebays. The forebays provide additional water storage and capture incoming sediments before they collect in the main portion of the pond (US EPA, 2009). The bottom elevation of these two forebays are near the seasonal high-water table (Bentley, 2010a) and cattails have historically dominated these areas.

1.3 Document Version

This guide is intended to be a living document that can be modified over time to reflect site-specific issues encountered at EOC. Each modification to this BMP should be documented in this section along with the date of modification.

Version Date Brief Description of Modification(s)

1.0 November 2017 N/A (original document)

2 Personnel

The Utilities Facilities and Water Distribution departments are both responsible for conducting inspections of and performing and/or contracting maintenance for portions of the stormwater collection system.

Responsibility for inspections and maintenance of the system is arranged according to the following hierarchy:

Figure 2-1. EOC Stormwater Control System Inspection and Maintenance Responsibility Hierarchy

2.1 Utilities Facilities Manager

The Utilities Facilities Manager will be responsible for the review, approval, and placement of all inspection worksheets in the operating record. If an inspection reveals a deficiency in system operation, the Manager, in collaboration with Environmental Permitting and Compliance, will review and authorize maintenance work orders submitted by the Utilities Facilities Lead to address the deficiencies.

If a deficiency shows that the stormwater control system is not functioning as designed, the Manager will be responsible for completing and forwarding the Exceptions Report (Form 62-330.311(1)), attached as

Appendix H, to Environmental Permitting and Compliance as soon as possible – the Exceptions Report must be submitted to the District within 14 days of deficiency observation, per Condition 24 of the site permit. The Manager will also designate a repository for completed inspection records and other stormwater control system documents which can be reviewed by District staff during normal business hours, per permit requirements. The Manager will send a copy of each document placed in the repository to Environmental Permitting and Compliance. Please see Section 7 for additional information on record keeping.

2.2 Water Distribution Supervisor

The Water Distribution Supervisor will be responsible for conducting weekly inspections of two storm drain inlets and maintaining parking surfaces in the Building 3 parking lot area (shown in Appendix J), and completing monthly log sheets that document the upkeep of this area. As needed, the Supervisor will clean/replace the storm drain filters near the material storage bays and schedule sweeping of the Building

3 parking lot area per the outcome of the weekly inspections. The Supervisor will provide a copy of the monthly log sheet to the Lead and to the Manager each time a log sheet is completed.

2.3 Utilities Facilities Lead

Except for the material storage bay area inspection items discussed above, the Utilities Facilities Lead will be responsible for conducting all routine and non-routine inspections of all EOC stormwater control infrastructure and completing forms which detail the results of these inspections. However, due to the frequent use and changing nature of the material storage bay area, the Lead will review the conditions noted in the monthly log sheet completed by the Supervisor and note any deviations in the monthly inspection worksheet. The Lead will sign and submit all completed forms (including the forms received from the Supervisor) to the Manager.

The Lead will be responsible for coordinating all preventative and corrective maintenance tasks necessary to keep site stormwater control infrastructure operating according to the standards included in this BMP.

As necessary, the Lead will designate specific maintenance tasks to Utilities Facilities Technicians and/or contracted grounds maintenance entities.

2.4 Utilities Facilities Technicians

Utilities Facilities Technicians are responsible for conducting any maintenance tasks as assigned by the

Lead or Manager.

3 Inspections

Inspections are conducted to evaluate whether the procedures outlined in this BMP are being followed, to assess the need for repair and maintenance, and to meet District permit requirements. Maintenance can be broadly categorized into functional maintenance and aesthetic maintenance; however, these two categories will often overlap (US EPA, 2004a).

While functional maintenance is not explicitly mandated by SJRWMD (2010), the permit does require inspections “to determine if the system is functioning as designed and permitted”; functional maintenance is imperative for GRU to achieve permit-compliant inspection results. The permit further requires that “if at any time the system is not functioning as designed and permitted, then within 14 days, the entity shall submit an Exceptions Report to the District, on form number 40C-42.900(6), Exceptions

Report for Stormwater Management Systems Out of Compliance.” Example indications that functional maintenance is necessary include broken/damaged/obstructed drainage infrastructure.

Aesthetic maintenance is another critical part of this BMP plan. If ignored, aesthetic maintenance issues can lead to functional maintenance issues. Aesthetic maintenance enhances public acceptance of the site, thereby allowing it to more readily integrate into the community (US EPA, 2004a) and a visually-appealing stormwater system can increase property values (US EPA, 2009). Aesthetic maintenance is particularly important for high-profile facilities. Examples of aesthetic maintenance include trash removal and pond bank landscaping.

Inspection tasks to assess for both functional and aesthetic maintenance needs are covered by this BMP.

Specifically, this BMP provides inspection guidance for 2 types of inspections: monthly and post-storm;

corresponding inspection forms are attached as appendices A and B, respectively. Based on his or her understanding of the design of the stormwater system (please see the design drawings and Section 1.2 for more information), it is the responsibility of the Lead and the Manager, in collaboration with

Environmental Permitting and Compliance, to decide whether the system is functioning as designed and whether to submit an Exceptions Report to SJRWMD.

Inspectors should bring a camera to take pictures of system deficiencies. Any item marked as “Needs

Attention” in the inspection worksheet should be discussed in detail in the Notes section; a minimum level of detail includes a specific description of the deficiency, its location, what actions are proposed to address the issue, and an estimated date of repair or corrective action.

3.1 Monthly Inspection Guidance

While monthly inspections are specified in this BMP, additional inspections may be necessary, particularly during the rainy season. The Gainesville rainy season generally occurs from May through September (GRU, 2016).

3.1.1 Collection and Conveyance Infrastructure

3.1.1.1 Storm Drains

The storm drains at the site are located on both paved and unpaved surfaces. These structures should be inspected for blockage/obstruction as a part of routine inspections. Table C-1 and Figure C-1, and Table

C-2 and Figure C-2 of Appendix C respectively present a summary of the location and number of storm drains located throughout the northern and southern portions of the site.

Sediment/hydrocarbon traps are installed in the grated inlet(s) located adjacent to the material storage bays. These traps should be checked during each inspection and cleaned as necessary to maintain surface drainage. These filters should not be cleaned over paved surfaces – any clean sediments may be rinsed out over a grass-covered surface that is located at least 60 feet from any stormwater control system component.

3.1.1.2 Outlets

Pipe outlets at the site typically are mitered end sections placed above riprap aprons. As part of routine inspections, all outlets should be inspected for blockage/obstruction and erosion. It should be noted that many of the outlets may be underwater for a significant portion of the year and will not be accessible for inspection.

3.1.2 Wet Detention Ponds

3.1.2.1 Pond Banks

Pond banks should be routinely inspected for erosion, litter and vegetation quality. Grass should generally be maintained from 6-8 inches, but should not be cut lower than 4 inches (US EPA, 2009).

3.1.2.2 Flattop Risers

Flattop risers have several different flow control features which vary from pond to pond. Similar to the inlet collection and conveyance features described previously, pond flattop risers should be inspected for blockage/obstruction as part of routine inspections.

Flattop risers (Figure 3-1) may have one or more of the following drainage features that should observed during each routine inspection for obstruction and/or damage.

• Grates – grates are intended to prevent larger pieces of debris from entering and obstructing the RCP. Flattop risers that do not have a skimmer will be more prone to obstruction.

• Weirs – weirs are the rectangular holes located on the side of the concrete riser vault.

Weirs should be inspected for obstruction.

• PVC Tee – depending on the pond, the PVC Tee may or may not have an orifice located on the bottom leg of the tee. PVC Tees should be inspected for damage and the orifices

(or openings) should be inspected for obstruction. The inspector should look into the flattop riser to confirm the low-flow discharge through the PVC whenever possible, as these small openings are prone to clogging.

• Skimmers – skimmers are designed to prevent floating debris and oils/grease from leaving the pond. These skimmers should be inspected for damage (e.g., cracks, broken or misaligned support brackets) and for vegetation obstruction.

Figure 4-3 presents an image of a flattop riser with labeled flow control features.

Figure 3-1. Flattop Riser Flow Control Features

3.1.2.3 Aquatic Vegetation

Aquatic vegetation (e.g., cattails, reeds) should not obstruct any stormwater device. It also should not occupy more than 50% of the water surface.

3.1.2.4 Aerators

All aerator cabinets should be undamaged and cabinet vents should be free from obstruction. Above-grade air lines should be inspected for damage and cracks. The inspector should verify that all diffuser heads connected to each cabinet are operational. The inspector should observe the pond surface water quality near each diffuser head air bubble rise locations for increased turbidity.

3.1.2.5 Turbidity

Elevated levels of turbidity have historically been visually observed in the aerated ponds at the site, and this turbidity appears to be related to the operation of pond aerators. As required by the District

(SJRWMD, 2014), GRU must monitor the aerated ponds to ensure that the turbidity of the discharged water does not exceed 29 nephelometric turbidity units (NTUs) above the background condition in the receiving waters. Elevated turbidity levels are harmful to aquatic ecosystems (US EPA 2012, NOAA 2017);

low turbidity levels should be maintained regardless of whether the ponds are actively discharging to the surrounding wetlands. Increased levels of turbidity and sedimentation will also increase the rate of clogging of conveyance infrastructure and will increase the rate of corrective maintenance needed.

Based on discussion with District staff, it appears that wetland background turbidity levels are generally low - if the water of any pond appears cloudy, this indicates that an excessively high turbidity level is present and the inspector should conduct corrective maintenance as soon as possible according to Section 5.2.4 (or Section 5.2.3 if the turbidity appears to be green in color or related to the presence of algae).

3.1.3 Pond 600

In addition to the inspection items included in Section 4.1.2.1 and 4.1.2.2, the cleanout access points (i.e., metal caps with concrete collars) should be free of grass, sediment and/or debris; and the overland weir should be free of trees, shrubs and other woody vegetation. An unobstructed flow path should be maintained through any vegetation growing in the forebays located at the pond’s principal stormwater entry points (i.e., S608, S614).

3.1.4 Wetlands

Wetland banks should be inspected for trash and erosion.

3.1.5 Material Storage Bays

Material storage bays should be inspected to verify that all material piles are covered, contained within their bays, and that there is no indication that material has washed into storm drains.

Sediment/hydrocarbon filters located in nearby grated inlets should be checked to see if cleaning is necessary.

3.2 Post-Storm Inspection Guidance

A post-storm inspection should be conducted following any major storm event (e.g., tropical depressions, tropical storms, hurricanes). Post-storm inspections have two purposes: to identify if there are any subsurface obstructions in RCPs, and to assess whether Pond 600 is failing to achieve its design drawdown rate. A post-storm inspection form is attached as Appendix B.

3.2.1 RCP Obstructions

As soon as possible following any major storm event, all storm drains should be inspected for standing water to help identify any potential blockages in underground piping. If an obstruction is suspected in an

RCP, the inspector may also observe the outlet of the RCP for a low-flow condition. Any deficiency should be addressed as described in Section 5.2.1. Storm drain locations are presented in Appendix C. Outlet locations are presented in Appendix D and Appendix F.

If the water of any pond appears cloudy, this indicates that an excessively high turbidity level is present and the inspector should conduct corrective maintenance as soon as possible – see Section 5.2.4.

3.2.2 Pond 600

As described previously, the underdrain system in Pond 600 was designed to drain approximately 316,000 gallons of stormwater over 36 hours (Bentley, 2010b). Depending on the water level in Pond 600, this is the same as a water level drop of approximately 0.40 – 0.48 feet (or 4.8 – 5.8 inches) over a 3-day period. The inspector should install a staff gauge or some other graduated marker and measure the Pond 600 water level as soon as possible following the end of the storm event. After a minimum of 3 days (i.e., 72 hours) have passed, the inspector should return and measure the new water level. If the water level of Pond 600 drops by less than 1.6 inches per day, the inspector should follow the corrective maintenance procedures detailed in Section 5.2.6.

4 Pond Bottom Surveys

A survey of the pond bottoms should be conducted every five years to evaluate the need for dredging/sediment removal from the ponds, as well as the forebays located in Pond 600. As suggested by

US EPA (2009), dredging/sediment removal should occur any time more than 50% of the pond volume is lost. To conduct this evaluation, GRU will need to hire a licensed land surveyor to conduct a survey of both dry and submerged pond bottom surfaces. GRU will then need to compare the surveyed surface to the original, as-built pond bottom grades. The initial 5-year survey should be scheduled as soon as possible.

5 System Operation and Maintenance

As designed, the stormwater control system can be operated without daily supervision and/or adjustments. However, regular maintenance is critical to ensure the system’s continued and efficient function. As described previously, maintenance can be broadly classified into functional and aesthetic maintenance. Functional maintenance can be further classified into preventative maintenance (i.e., tasks routinely performed to prevent system malfunction) and corrective maintenance (i.e., tasks performed on a non-routine basis to restore system functionality) (US EPA, 2004a). The following section is organized according to preventative, corrective, and aesthetic maintenance tasks.

5.1 Preventative Maintenance

5.1.1 Vegetation Management

In general, the use of fertilizer and herbicides is discouraged for the management of vegetation in and around the stormwater control system. Herbicides may impact the growth of plant species other than those being targeted and fertilizers have the potential to wash into ponds and wetlands causing harmful algae blooms; algae blooms may result in a decrease in pond oxygen levels, which may result in fish kills and other negative impacts to onsite ponds and adjacent wetlands

If the water level of Pond 600 drops by less than 1.6 inches per day, corrective maintenance will be necessary – see Section 5.2.6.

5.1.1.1 Mowing

Pond and wetland bank mowing should be scheduled on a bi-weekly basis (minimum) during the growing season, but may be adjusted to a monthly (or less frequent) basis during the dry season. As described in

Section 3.1.2.1, mowing should be conducted to allow pond and wetland bank grasses to remain between 6 and 8 inches in height, but not less than 4 inches (US EPA, 2009). Grasses cut below this height may experience stress due to insufficient blade length, which may lead to unvegetated, bare soil patches on bank slopes. Grasses allowed to grow above this range may allow the establishment of undesirable plant species and will negatively impact site appearance.

Leaves and grass clippings should be collected following pond bank mowing to prevent them from washing into ponds. These materials have the potential to decompose and allow nutrients to enter the stormwater system, causing algae blooms.

5.1.1.2 Volunteer Tree/Shrub Removal

Volunteer trees and shrubs (i.e., those not planted as part of the approved site landscaping plan - see

Appendix G) should be removed from the stormwater control system wherever they are identified.

5.1.1.3 Easement Clearing/Grubbing

The upkeep of easement/access paths (e.g., to stormwater control features in Wetland R1A and Pond

100) should be conducted monthly/quarterly and should be incorporated into the grounds maintenance contract. For equipment mobility, easements should be kept approximately 12-feet wide. Clearing, grubbing, and mowing associated with establishing and maintaining easements and access to stormwater infrastructure shall not extent beyond the limits of clearing as defined in the original design drawings

(Bentley, 2010a). Vegetation and debris generated from easement maintenance should be removed from the site or deposited in an unpaved onsite area located well away from onsite ponds, wetlands and drainage infrastructure.

5.1.2 Aerators

Pond aerator units (i.e., located in cabinets adjacent to Pond 300, 301, 402 and 400) should be maintained in accordance with the manufacturer’s service requirements. Based on manufacturer literature, aerator filters should be replaced and equipment should be checked on a quarterly basis (minimum). The manufacturer also recommends an annual application of electric contact cleaner. Please see Appendix E for more details.

5.1.3 Pond 600

On an annual basis, the contracted grounds maintenance entity should remove any trees, shrubs or other woody vegetation that grows within the riprap of the overland weir and should also remove any sediment or vegetation covering any of the cleanout access points of the underdrain system. Any material removed from these locations should be removed from the site or should be land applied onsite at a point well away (i.e., more than 60 feet) from any pond, drain, or other component of the system.

Mowing grass below 4 inches may lead to unvegetated, bare soil patches on bank slopes.

5.2 Corrective Maintenance

5.2.1 Infrastructure Damage or Obstruction

5.2.1.1 Inlets

Any obstruction of a ground surface inlet structure (i.e., curb inlets, drop inlets) should be cleared away as soon as possible. Similarly, any obstruction to or damage found in a drainage feature of a pond flattop riser should be removed or repaired as soon as possible. Care should be exercised whenever a stormwater control feature is unclogged – forces associated with rapid drainage can cause unsafe conditions for maintenance personnel. If unclogging a system feature looks like it may cause a safety concern, GRU should designate the repair work to a qualified contractor.

In the event water is observed to back up even after a visible obstruction is removed, GRU should consider maintenance procedures described in Section 5.2.1.3.

5.2.1.2 Outlets

Sediment and/or vegetation obstruction is one of the most likely events that would trigger the need for corrective maintenance at outlet structures. Depending on the degree of obstruction and resulting sediment/debris accumulation, it may be necessary to clean/flush out the pipe preceding the outlet. For more information on corrective maintenance of underground pipes, please see Section 5.2.1.3.

5.2.1.3 Underground Pipes

In addition to access by means of drop inlets (with removable grates), numerous manholes are located throughout the site at pipe joints and junctions. Once a clog has been identified or is suspected based on low flow or the absence of flow through pipe inlets and/or outlets, GRU should use the access points to confirm the presence of the suspected obstruction in accordance with all OSHA confined-space entry regulations and any other applicable federal, state and local regulations/requirements. As necessary, GRU should jet clean the compromised section of pipe.

The layout of the storm drain RCP network and associated access points can be found in drawings C-1400 through C-1413 of the design drawing set included as Appendix F.

5.2.1.4 Aerators

Aerators should be repaired whenever they cease to function as designed. Repair services may be acquired through manufacturer-recommended service providers; the manufacturer (Clean-Flo) can be contacted at 1-800-328-6656.

5.2.2 Bank Erosion

Bank erosion will typically occur because of either insufficient or distressed surface vegetation, obstructed/damaged stormwater system infrastructure, or a combination of these factors. Bank erosion

Confined-space entry must be conducted according to OSHA regulations and any other applicable federal, state and local regulations/ requirements.

should be repaired to reestablish the design grades. All exposed and/or disturbed earth surfaces should be revegetated and stabilized as soon as possible following erosion repair.

Stormwater systems are designed to minimize erosion. If bank erosion continues in the presence of well-established vegetation and properly-functioning infrastructure, GRU should seek engineering advice for redesign of the stormwater system in the problem area.

5.2.3 Algae Blooms

Algae blooms typically indicate that the water contains high levels of nutrients (e.g., nitrogen, phosphorus). Phosphorus is commonly the limiting nutrient for algae growth in lakes (Yang et al., 2008).

If algae blooms are observed in the ponds, the following corrective maintenance steps should be evaluated and/or implemented until algae levels are substantially reduced:

• Reduce the rate of fertilizer application to areas that drain to the impacted pond. The University of Florida Institute of Food and Agricultural Sciences (UF IFAS, 2017) provides general recommendations for the fertilization of grass on Florida soils. GRU should check with the contracted grounds maintenance entity to verify that fertilizer is not being applied over recommended levels.

• Remove grass clippings from mowing. Similar to fertilizer, grass clippings contain nutrients that may be released into the ponds if the clippings are not removed after mowing.

• Plant emergent vegetation along the waterline of the affected pond(s). These plants will compete with algae for the nutrients of the pond’s substrate (US EPA, 2009). A list of recommended emergent plant species for Florida stormwater ponds is included in Appendix I.

• Consider the implementation of a 10-foot wide no-mow buffer zone adjacent to the pond’s water line. These vegetation buffers help filter and prevent nutrient-laden runoff from entering the pond. They also improve pond bank stability (US EPA, 2009).

5.2.4 Pond Turbidity

Pond turbidity caused by the presence of algae should be addressed as described in the previous section.

Turbidity resulting from suspended sediments may be the result of dirt and debris washed into the ponds from surface erosion, from accumulation on paved surfaces, or from the suspension of pond sediments as the result of aerator operation.

Ponds with elevated levels of sediment turbidity should be closely observed to see if the source of the turbidity can be identified. If turbidity is noticeably higher near a specific stormwater inflow point, additional investigation of the stormwater inlet locations upstream of that point is warranted. Likewise, if turbidity is noticeably elevated near aerator bubble streams, the effect of reducing or turning off the airflow to the diffuser head(s) should be evaluated. The inspector should note that there are risks associated with reducing or turning off aerator airflow; the aerators provide dissolved oxygen to aquatic organisms and reducing airflow will lead to an increased risk of fish kills.

If increased turbidity is linked with aerator operation, GRU should consider re-location of the aerator diffuser head(s) since it is possible they have been covered with a layer of sediment. Per aerator manufacturer requirements, the new diffuser head location needs to be at the deepest part of the pond bottom. See the design drawing set, attached as Appendix E, for additional details on pond bottom elevations; most of the ponds have a flat bottom at their deepest point.

Even with the relocation of the diffuser heads, depending on the nature of the sediments that have accumulated at the bottom of the ponds, it may not be feasible to operate the diffusers without causing high turbidity levels. If elevated levels of sediment turbidity continue following diffuser relocation, GRU may need to consider dredging sediments from the pond bottoms or an alternative means of pond aeration.

5.2.5 Pond Sediment Accumulation

Sediment will accumulate at the bottom of all stormwater ponds over time as well as in the forebay areas of Pond 600. Sediment accumulation is a function of the amount of material being washed into the ponds and the quantity of pond vegetation. Pending the results of the 5-year inspection described previously, GRU should dredge/excavate and regrade pond bottoms to return them to their original design grades.

Excavation and dredging should be performed when the water elevations in the ponds are relatively low

– these activities should be conducted towards the end of the dry season. Sediment removal should not be conducted if the ponds are discharging to the wetlands surrounding the site; dredging/wet pond excavation has the potential to substantially increase pond turbidity levels and sediment removal must be conducted in a manner that prevents the violation of state water quality standards (i.e., see conditions

3, 4 and 22 of the site permit). It is critical that GRU stabilize all disturbed ground surfaces immediately following and (as possible) during pond excavation and regrading activities.

Sediments removed from the ponds may be disposed of offsite, but will likely need to be temporarily stored onsite for drying. The offsite disposal and transport of saturated sediments will be costly and

(depending on the disposal site) may be prohibited. One potential temporary drying area for excavated sediment is the southern portion of the training field. However, all sediment should be placed well away

(i.e., at least 60 feet) from any pond, drain, or other component of the system. It should be noted that there are several storm drains located in the southern portion of the training field – these features must be adequately protected prior to the deposition of any sediments.

If dewatering is necessary as a part of sediment removal, GRU is required to provide the District with a detailed dewatering plan at least two weeks prior to starting the dewatering process. Please see Condition

25 of the site permit for details on what this plan must include.

5.2.6 Pond 600

Pond 600 will require corrective maintenance if it does not achieve the design drawdown rate, as discussed in Section 3.2.2. The drawdown rate of Pond 600 may be improved by jet cleaning the underdrain pipes (using the cleanouts accessible on the pond’s bottom surface) and/or by loosening the soil directly above the underdrains to improve its permeability.

If GRU decides to jet clean the underdrain system, it should select a qualified contractor who implements a stormwater pollution prevention plan that precludes the discharge of sediment-laden water into adjacent wetlands that has turbidity more than 29 NTU above background water concentrations.

5.3 Aesthetic Maintenance

5.3.1 Litter Removal

Litter should be removed from the stormwater control system and surrounding wetlands whenever it is found. Litter detracts from the aesthetics of the stormwater control system and can accumulate to the point where system components can become obstructed and inoperable during storms events (US EPA, 2004a; US EPA, 2004b). Because flattop risers serve as the primary point of drainage for the wet detention ponds, they may serve as an accumulation point for floating vegetation, trash and other debris.

5.3.2 Landscaping

Landscaping efforts such as dead tree/shrub removal and replacement, weed removal, and mulch application should be conducted as a part of regular grounds maintenance contracts and should be conducted on a quarterly basis. Landscaping activities should be scheduled and executed to meet the conditions of the approved site plan, as provided in Appendix G.

5.3.3 Nuisance Vegetation

Some species of aquatic plants may dominate areas of the stormwater system. In North-central Florida, cattails and the common reed are often found in or near slow-moving or stagnant water bodies.

Historically, cattails have occupied a moderate portion of Pond 100 and the two stormwater forebay locations (i.e., located on the east and north side) of Pond 600.

While the presence of these plants is not necessarily problematic, their accumulation has the potential to cause several issues beyond aesthetics:

• Obstructing stormwater conveyance infrastructure - stands of cattails and other plants may grow directly in front of or around pipe discharge points or pond drainage points, impeding the design flow to and from these points.

• Increasing the rate of pond sedimentation – the decomposition of these plants resulting from the annual die-back which occurs at the end of the growing season will contribute to an increased rate of sediment build up on the pond bottom.

• Providing a habitat for mosquito larvae – when cattails die back in the fall, they provide a suitable environment for the growth of mosquito larvae (NCSU, 2006).

If GRU elects to remove aquatic vegetation, this activity should be conducted before winter die-off to prevent the release of nutrients into the water because of decomposition (US EPA, 2009). Harvested nuisance vegetation should be removed from the site to help prevent the re-establishment of the species as a result of seeds/roots being washed back into ponds/wetlands. Non-nuisance vegetation may be land applied onsite at a point well away (i.e., more than 60 feet) from any pond, drain, or other component of the system.

Any time monolithic stands of cattails or other emergent aquatic vegetation are removed, GRU may consider replacing this vegetation with a different emergent species or a variety of species to prevent/slow down reoccupation of the same area by the plant species that was just removed. A list of recommended water edge zone and bank zone plants for Florida stormwater ponds is provided in

Appendix I.

5.4 Summary of Routine Maintenance Activities

Table 5-1 below provides a summary of routine maintenance activities discussed in Section 5 of this BMP.

Table 5-1. Summary of Stormwater Control System Routine Maintenance Activities

Category Task(s) Frequency Location(s) Section

Vegetation

Management

Mowing

Bi-weekly/

Monthly

Wetland and Pond Banks

(and if dry) Pond Bottoms 5.1.1.1

Easement

Clearing/Mowing

Monthly/

Quarterly

Easement to Pond 100, Wetland R1A 5.1.1.3

Volunteer Tree/Shrub

Removal Quarterly Any Part of System 5.1.1.2

Landscaping

Planting Maintenance, Tree Maintenance, Weeding, Mulching Quarterly

Pond and Wetland

Landscaped Areas 5.3.2

Aerators Check/Replace Filters Quarterly

Pond 301, 300, 402, 400

Aerator Compressors 5.1.2

Apply Electric Contact

Cleaner Annually

Pond 301, 300, 402, 400

Aerator Compressors 5.1.2

Pond 600

Tree/Shrub Removal Annually Overland Weir 5.1.3

Remove sediment/vegetation from cleanout caps Annually Pond Bottom 5.1.3

Ponds Pond Bottom Survey 5 Years Pond Bottoms 4

6 Spills and Additional Concerns

6.1 Spills

In the event of a spill, GRU shall implement the procedures detailed in the most up-to-date version of the

Spill Prevention Control and Countermeasure (SPCC) Plan, as required per 40 CFR 112.

6.2 Site Construction

Any construction, demolition, renovation, or any other work that causes the disturbance of onsite soils shall be permitted under all applicable provisions of the Florida National Pollutant Discharge Elimination

System, District requirements, and local regulations (e.g., city, county). Any construction effort or any other activity which causes the disturbance of onsite soils should be conducted in a manner to stabilize all exposed soil surfaces as quickly as possible. Erosion and sedimentation control measures shall be implemented to prevent the release of sediment-laden water into the stormwater control system. Unless an erosion and sediment control plan is approved as part of the permit, sediment and erosion control measures must be implemented in accordance with Chapter 6 of the Florida Land Development Manual

(FDER, 1988), as required by Condition 4 of the site permit.

6.3 Onsite Material Storage Piles and Equipment Cleaning

A series of material storage bays is located directly west of Pond 301. These material piles should be covered and contained to preclude material washout and transport into stormwater collection infrastructure. Stockpile elevations should be controlled to prevent material from spilling over containment walls. Loose material that drops onto the surrounding pavement during the scooping and loading process should be immediately removed and relocated back into the appropriate material storage bay. Loose material should never be kept in exposed stockpiles on paved surfaces.

Similarly, dirt must not be rinsed from equipment over paved areas. Dirt should be rinsed from equipment over a grass surface located as far from ponds and storm drains as possible. The grass surface acts as a vegetative filter strip, which assists in the removal of particles from sediment-laden/turbid stormwater flows (US EPA, 2014c). Assuming the ground surface is mildly sloped, the vehicle rinse area should be at least 60 feet away from the closest system component; US

EPA (2014c) suggests that the sediment (i.e., total suspended solids) removal efficiency of vegetative filter strips levels off significantly when they are longer than 59 feet.

Cleaners (e.g., degreasers, solvents, detergents) must not be used for onsite equipment washing unless the rinse water is captured in a contained washout area and disposed of according to applicable permit conditions.

6.4 Dumpsters

All onsite lidded dumpsters used for waste disposal should be kept covered when not in use. Precipitation that collects on the bottom of dumpsters has the potential to become contaminated with the dumpster’s contents, and if there are any holes in the bottom of the dumpster, non-stormwater discharges can be released onto the surrounding ground surface. Uncovered waste also has the potential to attract wildlife searching for food – trash may be pulled out and deposited on the ground with the potential to be washed into the stormwater control system. While most lidded dumpsters are designed so that the lid stays down when not in use, the inspector should regularly monitor whether the lid is in place for all onsite dumpsters.

In the event dumpster lids are found to be regularly left open, the inspector should notify the Manager of the issue and the Manager should contact and discuss the issue with facility maintenance personnel.

7 Record Keeping

Per the site’s operating permit, GRU must keep a record of the following documents at the site:

Dirt should be rinsed from equipment over a grass surface located as far as possible from ponds and storm drains.

• A complete copy of the permit with all conditions, attachments, exhibits and modifications

• A record of each required inspection – inspection records must be available to District staff during normal business hours.

In addition to these documents, GRU should also keep a copy of the following documents in the operating record:

• Design Drawing Set of the Stormwater Control System (Bentley, 2010a)

• Calculation Report of the Stormwater Control System (Bentley, 2010b)

• As-Built Survey of the Stormwater Control System (FSM, 2011)

• Site Landscape Plan (MDG, 2010)

• Executed work orders authorizing corrective maintenance tasks

• Exceptions Reports submitted to the District

• SJRWMD (2014) letter requiring the monitoring of discharges from aerated ponds to ensure turbidity levels do not exceed 29 NTUs above the background condition of receiving waters

8 References

Bentley (2010a). Stormwater Management, Grading and Drainage for GRU Eastside Operations, Gainesville, Florida for Submittal to SJRWMD. Design drawing set prepared for Gainesville

Regional Utilities by Bentley Architects and Engineers. Last revised 16 February 2010.

Bentley (2010b). Stormwater Management Calculations for Gainesville Regional Utilities Eastside

Operations, Gainesville, Florida. Project No. 2006-024. Calculation Report Revised 16 February

2010 (Revision 6).

FDER (1988). The Florida Development Manual: A Guide to Sound Land and Water Management. Prepared by the Florida Department of Environmental Regulation. June 1988.

FSM (2011). As-Built Survey. Survey Date 18 August 2011. Certified by Flowers Surveying and Mapping, Inc. to Watson Construction, Skanska, Bentley Architects and Engineers, Inc.

GRU (2016). Gainesville Regional Utilities Deerhaven Generating Station Front-End Treatment Lime Sludge

Disposal Plan. Prepared for GRU by Innovative Waste Consulting Services, LLC. April 2016.

MDG (2010). GRU Eastside Operations Center, Landscape Ordinance Plan. Drawing set prepared by

McClain Design Group, Inc. Last revised 16 March 2010.

NOAA (2017). Turbidity.

https://oceanservice.noaa.gov/education/kits/estuaries/media/supp_estuar10e_turbinity.html.

Accessed 18 September 2017. National Ocean Service, National Oceanic and Atmospheric

Administration. Revised 6 July 2017.

NCSU (2006). Urban Waterways: Maintenance of Stormwater Wetlands and Wet Ponds. Prepared by

William F. Hunt, Assistance Professor and Extension Specialist, Biological and Agricultural

Engineering, North Carolina State University and Bill Lord, Area Environmental Agent, North

Carolina Cooperative Extension. August 2006.

SJRWMD (2010a). Individual Management and Storage for Surface Waters Technical Staff Report.

Application #:4-001-15619-3. Report prepared by the St. Johns River Water Management District, 7 April 2010.

SJRWMD (2010b). Permit Number 4-001-15619-3. GRU Eastside Operations. Authorized by the St. Johns

River Water Management District, 8 April 2010.

SJRWMD (2014). Re: GRU Eastside Operations, Permit No. 4-001-15619-3, Compliance Item No. 1186244.

Letter to H. Reid Rivers, Gainesville Regional Utilities from Barbara Hatchitt and Melissa Bryan

Parsons of the St. Johns River Water Management District. 14 November 2014.

UF IFAS (2013). Florida-Friendly Plants for Stormwater Pond Shorelines. ENH1215. Prepared by Gail

Hansen and Shangchun Hu for the Environmental Horticulture Department, Florida Cooperative

Extension Service, Institute of Food and Agricultural Sciences, University of Florida. May 2013.

UF IFAS (2017). General Recommendations for Fertilization of Turfgrasses on Florida Soils. SL21. Prepared by T.W. Shaddox for the Department of Soil and Water Sciences, Institute of Food and Agricultural

Sciences, University of Florida. Last revised February 2017.

US EPA (2004a). Stormwater Best Management Practice Design Guide, Volume 3 – Basin Best

Management Practices. EPA/600/R-04/121B. Developed for the National Risk Management

Research Laboratory, Office of Research and Development, United States Environmental

Protection Agency. September 2004.

US EPA (2004b). Stormwater Best Management Practice Design Guide, Volume 1 – General

Considerations. EPA/600/R-04/121. Developed for the National Risk Management Research

Laboratory, Office of Research and Development, United States Environmental Protection

Agency. September 2004.

US EPA (2004c). Stormwater Best Management Practice Design Guide, Volume 2 – Vegetative Biofilters.

EPA/600/R-04/121A. Developed for the National Risk Management Research Laboratory, Office of Research and Development, United States Environmental Protection Agency. September 2004.

US EPA (2009). Stormwater Wet Pond and Wetland Management Guidebook. EPA/833/B-09/001. Revised by the Environmental Protection Agency, February 2009.

US EPA (2012). Water: Monitoring and…