City of Bozeman. Construction Site Management Program

Transcription

1 City of Bozeman Construction Site Management Program Best Management Practice (BMP) Manual for Construction Sites Version 6 June 30, 2017

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3 Section 1 - Overview Table of Contents Manual Introduction 5 Permit Types 7 Local Erosion and Sediment Control Requirements 9 Operational and Administrative Controls 11 Section 2 - Perimeter Control Foam Wattle with Apron 13 Straw Wattle 15 Silt Fence 19 Compacted Earthen Berm 23 Sediment Trap 27 Section 3 - Infrastructure Protection Inlet Protection 31 Tracking Control 33 Dewatering from Excavated Areas and Wells 37 Section 4 - Pollutant Management Concrete Washout and Waste Management 41 Section 5 Final Stabilization Measures Post Construction Feature 47 Disturbed Area 53 Section 6 Single-Family Residential Single-Family Home Construction Site Protection Plan 55 3

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5 Overview Manual Introduction This manual provides Best Management Practices (BMP) designed to mitigate pollution generated from construction activities. The City of Bozeman encourages developers, engineers, and contractors to use this resource to develop and implement required stormwater permits further detailed on Page 4. Stormwater is rain and snowmelt that flows over hard surfaces and landscapes that does not infiltrate into the ground. Stormwater picks up pollutants, such as sediment, trash, animal waste, fertilizers, oils, hydrocarbons, and grease, as it moves over these surfaces. Stormwater then enters curb inlets, passes through a network of underground pipes, and dumps into local rivers without treatment. The City of Bozeman works to improve the quality of stormwater runoff to ensure local waterways stay healthy enough so residents can safely fish, recreate, and swim. One of the largest local stormwater pollution sources is uncontrolled stormwater runoff from unprotected construction sites. Stormwater runoff from unprotected construction sites carries sediment and other pollutants offsite, causing degradation of rivers and infrastructure. A one-acre construction site can lose tons of sediment to erosion per year. It is important that construction professionals manage stormwater on their sites to navigate the City s development process, avoid enforcement penalties, and ensure Bozeman continues to be The Most Livable Place. Image 1 Stormwater dumping into Bozeman Creek Image 2 Clogged stormwater pipe from construction 5

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7 Overview Permit Types The City of Bozeman requires that project owners have an approved stormwater permit before initiating construction activities. Staff encourages submitters to schedule a pre-submittal meeting where minimum expectations, recommendations, and areas of concern are identified, decreasing preparation, approval, and implementation efforts. Staff review, comment on, and, when deemed adequate, approve all stormwater permits. Project owners that do not submit or submit inadequate permits will not receive a building permit until one of the following is approved: Single-family home construction: Project owners must submit a Single-Family Erosion and Sediment Control Construction Permit. There is no fee associated with this permit. Multi-family, commercial, utility, demolition, and paving projects with a total land disturbance less than one acre: Project owners must submit an Erosion and Sediment Control Construction Permit - Sites Less than 1 Acre. There is no fee associated with this permit. See the Attachments section for a detachable permit. **Presubmittal meeting with staff is highly encouraged. Multi-family, commercial, utility, demolition and paving projects with a total land disturbance greater than one acre: Project owners must submit a Montana Department of Environmental Quality (MDEQ) Notice of Intent, Stormwater Pollution Prevention Plan, and a Notice of Termination to the City of Bozeman and MDEQ. There is no City of Bozeman fee associated with this permit. See the Attachments section for a detachable permit. **Presubmittal meeting with staff is highly encouraged. Image 3 Construction-related pollution event Image 4 Clogged stormwater inlet from construction 7

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9 Overview Local Erosion and Sediment Control Requirements The City of Bozeman requires that project owners meet the following local erosion and sediment control requirements when preparing and enacting a stormwater permit for their site. They exist to provide a consistent message to contractors, improve permit content, and promote cleaner sites. Project owners must: 1. Protect inlets: Inlets receiving site runoff require BMPs that filter stormwater before flowing into underground infrastructure. Approved options include drop inlet protection. 2. Contain disturbed areas: Project boundaries require BMPs that contain stormwater flowing from disturbed areas. Approved options include foam wattle, straw wattle, silt fence, and compacted earthen berm. 3. Mitigate tracking: Exit points require BMPs that prevent the tracking of debris offsite. Approved options include angular rock and a cattle guard/rock hybrid trackpads. 4. Control concrete waste: Concrete activities require BMPs that allow for the containment and disposal of pollutants generated through masonry activities to prevent environmental contamination. Common regulated activities include concrete pours, masonry tool washing, and curb cutting. Approved options include reusable/disposable products, prefabricated roll-offs or containers, lined below-ground containment, and lined above ground containment. 5. Contain material stockpiles: Material stockpiles, not already contained within an existing perimeter control, require perimeter BMPs that prevent erosion and displacement of loose material. Approved options include foam wattle, straw wattle, silt fence, compacted earthen berm, and tarps/plastic sheeting. 6. Manage dewatering flows: Pumping activities require BMPs that filter water before entering underground infrastructure or waterways. Approved options include filter treatment units, land application, or wells. Dewatering discharges to state waters are a permitted activity under the authority of the MDEQ. 7. Protect post-construction stormwater features: Post-construction stormwater features, such as retention and detention ponds, require BMPs that protect and stabilize their side slopes and bases during and after construction activities. Approved BMPs include riprap, reinforced fore-bays, check dams, crimped straw mulch, and rolled erosion control products. 8. Stabilize disturbed areas: Disturbed areas require BMPs that prevent erosion of barren ground. Approved options include surface roughening, crimped straw mulch, wood mulch, rolled erosion control products, riprap, and sod. 9

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11 Overview Operational and Administrative Controls Introduction Operational and administrative control BMPs help keep construction sites clean and in compliance. The following are things to consider when preparing and implementing a stormwater permit: Communication Ensure all contractors and subcontractors are aware of their roles and responsibilities Site Barrier Utilize site barriers to control the flow of vehicles and equipment. Several types exist, including concrete blocks, construction fencing, and cones. Off-Site Parking Utilize off-site parking to control tracking by reducing vehicle trips onto disturbed areas. Spill Prevention and Response Utilize a spill kit to clean up leaks and spills that occur. All parties should know its location and proper use. Fleet Management Utilize preventative maintenance to identify and eliminate leaks and drips of hydraulic fluid, gas, oil, etc. from equipment and vehicles. Preservation of Existing Vegetation Utilize preservation of existing vegetation techniques to reduce the amount of erodible area on a job site. Street Sweeping Implement a regular street sweeping program to remove all dirt and construction debris from streets, alleys, and parking lots. Good Housekeeping Keep a clean site by developing and adhering to a waste management plan that includes protocols for trash disposal, sanitary facility cleaning, and proper storage of chemicals. Image 5 Site Barrier Image 6 Spill Kit Image 7 Equipment Management Image 8 Tarped stockpile 11

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13 Introduction Foam wattle slows and ponds stormwater flowing from small construction sites, including ground disturbance, pollutant storage, and material stockpile areas. Various proprietary foam wattles exist and are available from local suppliers. Contractors must consider their site s size, soil condition, and topography before selecting and installing this BMP. Installation Requirements Install foam wattle: Perimeter Control Foam Wattle with Apron before construction activities per the manufacturer s specification perpendicular to the slope trenched 1 below grade and backfilled with compacted soil placed 2 min. away from the toe of stockpiles or slopes installed with ends turned upslope for 2 min. Inspection and Maintenance Image 9 Properly installed straw wattle. Image 9 Properly installed foam wattle with apron Inspect foam wattle weekly, before rain events, and after rain events to ensure it is functioning. If not, complete one of the following tasks: Repair or Replace torn, flattened, pulled out, or unraveled foam wattle. Repair holes by resecuring the netting using wire, twine, or rope. Cut out and replace degraded sections, ensuring to overlap with existing foam wattle. Replace stakes that have been broken, dislodged, or removed using a mallet or hammer. Maintain once sediment accumulation reaches a depth of 3. Remove collected sediment using hand tools. Remove once the site reaches final stabilization. Fill, compact, and vegetate areas of ground disturbance to blend with adjacent ground and throw away or reuse the foam wattle. 13

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15 Introduction Straw wattle slows and ponds stormwater flowing from small construction sites, including ground disturbance, pollutant storage, and material stockpile areas. Approved straw wattle consists of weedfree straw wrapped in UV-degradable netting. Contractors must consider their site s size, soil condition, and topography before selecting and installing this BMP. Installation Requirements Install straw wattle: Perimeter Control Straw Wattle before construction activities per the following specification perpendicular to the slope trenched 2 below grade and backfilled with compacted soil secured with 16 wooden stakes at alternating 45 angles every 3 and ends turned upslope for 2 min. overlapped with 1 min. when joining two sections placed 2 min. away from the toe of stockpiles or slopes **Note: Not to be installed in areas of concentrated flow Inspection and Maintenance Image 10 Properly installed straw wattle. Inspect straw wattle weekly, before rain events, and after rain events to ensure it is functioning. If not, complete one of the following tasks: Repair or Replace torn, flattened, pulled out, or unraveled straw wattle. Repair holes by resecuring the netting using wire, twine, or rope. Cut out and replace degraded sections, ensuring to overlap with existing straw wattle. Replace stakes that have been broken, dislodged, or removed using a mallet or hammer. Maintain once sediment accumulation reaches a depth of 3. Remove collected sediment using hand tools. Remove once the site reaches final stabilization. Fill, compact, and vegetate areas of ground disturbance to blend with adjacent ground and throw away waste. 15

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19 Introduction Silt fence slows and ponds stormwater flowing from construction sites, including land disturbance, pollutant storage, and material stockpile areas. Approved silt fence consists of woven geotextile fabric attached to wooden stakes. Contractors must consider their site s size, soil condition, and topography before selecting and installing this BMP. A co-benefit of silt fence is that it functions as an operational control limiting site access. Installation Requirements Install silt fence: Perimeter Control Silt Fence before construction activities per the following specification perpendicular to the slope positioned with stakes on the down gradient side trenched 6 below grade in a J configuration and backfilled with Image 11 Properly installed silt fence compacted soil trenched with 3 min. wooden stakes every 10 with ends turned upslope for 5 min. placed 2 min. away from the toe of stockpiles overlapped with 1 min. when joining two sections **Note: Not to be installed in areas of concentrated flow Inspection and Maintenance Image 1 Properly installed silt fence Inspect silt fence weekly, before rain events, and after rain events to ensure it is functioning. If not, complete one of the following tasks: Repair or Replace ripped, torn, detached, or flattened silt fence. Repair by using a patch or duct tape to cover small holes and a staple gun to re-secure fabric to the stakes. Cut out and replace severely degraded sections, ensuring to overlap with existing silt fence. Replace stakes that have been broken, dislodged, or removed using a mallet or hammer Maintain once sediment accumulation reaches a depth of 1/3 of its height. Remove collected sediment using hand tools. Remove once the site reaches final stabilization. Fill, compact, and vegetate areas of ground disturbance to blend with adjacent ground and throw away waste. 19

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23 Introduction Perimeter Control Compacted Earthen Berm Compacted earthen berms slow, pond, and divert stormwater flowing from construction sites, including ground disturbance, pollutant storage, and material stockpile areas. Approved compacted earthen berms consist of soil or stone. Contractors must consider their site s size, soil condition, and topography before selecting, sizing, and installing this BMP. Often, contractors use compacted earthen berms to divert stormwater to a sediment trap. Installation Requirements Install compacted earthen berms: before construction activities per the following specification installed with a height of 2 min. and width of 3 min. and ends turned upslope for 5 min. stabilized with crimped mulch or surface roughening Inspection and Maintenance Inspect compacted earthen berms weekly, before rain events, and after rain events to ensure they are functioning. If not, complete one of the following tasks: Repair washed out, eroded, and flattened compacted earthen berms. Repair with a piece of equipment or hand tool capable of excavating, contouring, and compacting back to its original design. Maintain once sediment accumulation reaches 1/3 of its height. Use equipment or hand tools to remove. Remove once the site reaches final stabilization. Fill, compact, and vegetate areas of ground disturbance to blend with adjacent ground. Image 12 Installed compacted earthen berm Image 13 Conveyance ditch and compacted earthen berm 23

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27 Introduction Perimeter Control Sediment Trap Sediment traps capture and hold stormwater flowing from construction sites, including ground disturbance, pollutant storage, and material stockpile areas. Approved sediment traps consist of an excavated area with an armored overflow. Contractors must consider their site s size, soil condition, and topography before selecting, sizing, and installing this BMP. Installation Requirements Install sediment traps: before construction activities per the following specification installed with an overflow consisting of rip-rap underlain with a nonwoven geotextile designed with a volume of 1,890 cubic feet (70 CY) of storage per acre of contributing drainage area maximizing distance between the inlet and armored outlet to facilitate settling Inspection and Maintenance Inspect sediment traps weekly, before rain events, and after rain events to ensure they are functioning. If not, complete one of the following tasks: Repair washed out or eroded sediment traps. Repair with a piece of equipment or hand tool capable of excavating, contouring, and compacting back to its original design. Maintain once sediment accumulation reaches 2/3 of its height. Use equipment or hand tools to remove. Remove once the site reaches final stabilization or transition to post-construction BMP. Fill, compact, and vegetate areas of ground disturbance to blend with adjacent ground. Images 14 and 15 Sediment trap and armored overflow 27

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29 **Note: Taken from MDT s December 2016 Erosion and Sediment Control Best Management Practices Manual 29

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31 Introduction Infrastructure Protection Inlet Protection Inlet protection filters stormwater before flowing into the City s infrastructure. Inlet protection is the last line of defense, and the City requires its use to be in conjunction with other erosion and sediment control BMPs. Premanufactured devices designed to drop inside inlets are the only approved types. Multiple options exist online and at local retailers. Installation Requirements Install inlet protection: before construction activities per the manufacturer s specification Inspection and Maintenance Image 16 Properly installed drop inlet protection. Image taken from Inspect inlet control weekly, before rain events, and after rain events to ensure it is functioning. If not, complete one of the following tasks: Replace damaged inlet protection. Maintain by removing accumulated sediment using equipment or hand tools. Remove once the site reaches final stabilization. 31

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33 Introduction Offsite tracking control removes sediment from vehicle tires before exiting construction sites. The City allows two types. Both utilize geotextile and 3-6 angular rock. One option includes a cattle guard platform. Contractors must consider their site s volume of traffic, underlying soil condition, and site constraints before selecting and installing this BMP. Approved Options 1. Install angular rock: Infrastructure Protection Tracking Control before construction activities per the following specification underlain with a geotextile for separation between undisturbed soils and rock surfaced with 1 min. depth of 3-6 angular rock designed with a length that allows two full tire rotations 2. Install cattle guard and cobble hybrid: before construction activities per the following specification underlain with a geotextile for separation between undisturbed soils and rock designed with a 12 min. by 20 min. cattle guard with sediment capture bay below surfaced with 1 min. depth of 3-6 angular rock Inspection and Maintenance Image 17 Properly installed cattle guard entrance Inspect tracking control weekly, before rain events, and after rain events to ensure it is functioning. If not, complete one of the following tasks: Maintain once the aggregate and cattle guard fill with sediment. Refresh the surface by turning over the aggregate. Remove once there is a permanently stabilized site entrance. Fill, compact, and vegetate areas of ground disturbance to blend with adjacent ground. 33

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37 Introduction Infrastructure Protection Dewatering from Excavated Areas and Wells Dewatering controls manage and treat pumped water before it flows into infrastructure or waterways. Contractors must consider the expected volume of water, duration, and site condition before selecting and installing dewatering BMPs. Approved Options 1) Well Dewatering Used to lower the water table during utility line and foundation installation. Achieved through the use of well(s) and pumps tied together in a network that discharge to a predetermined location(s). Discharge location(s) may include waterways, stormwater infrastructure, or vegetated lands. Installation requirements include: placed within 15 x 15 undisturbed area contained initial turbid discharge (purging of well) reinforced discharge location preventing erosion 2) Excavation Dewatering Used to remove accumulated water from an excavation. Achieved through the placement of a pump in the excavation, which pushes water through a hose, filter, and then a predetermined discharge location(s). Discharge location(s) may include stormwater infrastructure and vegetated lands. Installation requirements include: Proprietary bag, cartridge, or media treatment unit with a 1 micron filter capability. Rain for Rent and Baker Corporation are examples of companies that manufacture treatment units capable of meeting this standard. Maintenance and Install Requirements Inspect routinely to ensure dewatering controls are functioning and resulting in a clear discharge. If not, halt dewatering immediately and: Image 18 Proprietary bag filtration unit Maintain treatment unit per manufacturer s recommendation. Monitor and Maintain discharge location(s) if any noticeable erosion is identified by moving the hose or refortifying the ground surface using 3-6 cobble or stone. Remove once the site reaches final stabilization and is no longer required. Fill, compact, and seed areas of ground disturbance to blend with adjacent ground. 37

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41 Introduction Pollutant Management Concrete Washout and Waste Management Concrete washout is a toxic slurry generated from the washing of mixer chutes, pump trucks, and other masonry equipment. Contractors must consider their sites expected volume of washout and site constraints before selecting and installing one of the following approved BMPs. Approved Options 1) Reusable or Disposable Product 2) Prefabricated Roll Off or Container 3) Lined Below Ground Containment 4) Lined Above Ground Containment Installation Requirements Install concrete washouts: before concrete and masonry work per this manual or manufacturer s specification clearly marked with signage stating Concrete Washout Area of adequate capacity and structure to prevent spill and splash over Maintenance and Inspection Requirements Inspect concrete washouts before and after rain events to ensure they are functioning. If not, complete one of the following: Image 19 Reusable or disposable product Image 20 Prefabricated roll off Repair if the liner is leaking or washout is in a state of disrepair. Maintain when the facility reaches 75% capacity. Remove or evaporate clear washout water. Remove or recycle all solids and dispose into a roll off dumpster, haul trailer, or solid waste receptacle. Remove concrete washout once the site reaches stabilization and is no longer required. If applicable, fill, compact, and seed areas of ground disturbance to blend with adjacent ground. 41

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47 Introduction Final Stabilization Measures Post Construction Feature A post construction feature is an engineered pond designed and constructed to capture, infiltrate, and treat polluted stormwater flowing from roads, yards, parking lots, and driveways. The proper installation, stabilization, and maintenance of a post construction feature is necessary to ensure it functions properly, reducing negative impacts on local waterways. Once excavated, the City requires that post construction feature s side slopes and basin bottoms are stabilized using an erosion control product. Installation Requirements Install erosion control product: immediately after the post construction is constructed throughout the entire feature, including side slopes and bottom per the following specification Maintenance and Inspection Requirements Contractors must inspect erosion control products before and after rain events to ensure they stay secured to the ground and adequately stabilize disturbed areas. If not, complete the following: Repair if the erosion control product has loosened, is no longer covering disturbed area, or is in a state of disrepair. Image 19 Properly stabilized post construction feature 47

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49 **Note: Taken from MDT s December 2016 Erosion and Sediment Control Best Management Practices Manual 49

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51 **Note: Taken from MDT s December 2016 Erosion and Sediment Control Best Management Practices Manual 51

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53 Final Stabilization Measures Disturbed Area Introduction Stabilization measures reduce erosion, increase infiltration, shorten slope lengths, slow the flow of water, and minimize raindrop impact of disturbed areas during and after construction activities. Stabilization measures can be temporary or permanent depending on their type and application. Approved Options 1. Surface Roughening: Consists of 3 min. depressions running perpendicular to slopes using equipment, such as a grouser or sheep s foot. 2. Crimped Straw Mulch: Consists of weed-free straw with a 12 min. length evenly distributed at a rate of 4000 lbs/acre and crimped into the soil. Straw blowers and hand broadcasting are useful distribution methods. Flat shovels and disc plows work well for crimping. Image 20 Surface Roughening Image 21 Crimped Straw Mulch 3. Wood Mulching: Consists of shredded wood and compost evenly distributed. Apply wood mulch and compost to a depth of Rolled Erosion Control Products: Consists of biodegradable erosion control blanket composed of fibers such as jute, straw, coconut, or a combination of straw and coconut fibers. Installation criteria to consider: anchor slots, overlapping adjacent blankets, check dams, and staking. See page 47 for an installation specification. Image 22 Wood Mulching 5. Sod: Immediately stabilizes disturbed areas. Consider sod type, soil preparation, soil amendments, and irrigation until establishment. Image 23 Erosion Control Product 53

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55 Single-Family Residential Single-Family Home Construction Site Protection Plan Stage of Construction and Timming of BMP Implementation # Minimum Expectation Stage 1 - Foundation Stage 2 - Utilities Stage 3 - Structure Stage 4 - Flat Work Stage 5 - Landscaping 1 Protect Inlets 2 Contain Disturbed Area 3 Mitigate Tracking 4 Control Concrete Waste 5 Contain Material Stockpiles 6 Manage Dewatering Flows Example BMPs Drop inlet protection // Cost: $100 (reusable) Foam wattle, straw wattle, silt fence, or earthen berm // Cost: $50 - $100 (reusable) Gravel drive entrance // Cost: $150 Prefabricated roll-off or lined container // Cost: $20-$30 Tarp or within perimeter control // Cost: $25-$50 Land apply or filter unit // Cost: ~$500 7 Stabilize Disturbed Area Sod // Cost: n/a Contain Disturbed Area Straw Wattle Control Concrete Waste Washout Bag Protect Inlets Drop Inlet Protection Manage Dewatering Flows Filter Unit Mitigate Tracking Gravel Drive Entrance Stabilize Disturbed Area Sod 55

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57 Single-Family Residential Single-Family Home Construction Site Protection Plan 57