City of Englewood : Floodproofing study & outfall system plan (OSP) Update

Introduction

Severe flooding during the summer of 2018 brought into focus the need to reduce flood hazard in Englewood. The City of Englewood contracted with Calibre Engineering to evaluate ways to reduce flood hazard in some of the City’s most predominantly affected watershed basins, as identified in the Scope of Work. The evaluation included an update of the City’s OSP, a conditions assessment of the stormwater pipe at Oxford and Santa Fe, and presentation of floodproofing techniques for residents. This website documents that evaluation and presents findings, including ways that Englewood residents can protect their homes. Finally, this website presents projects that Englewood can implement to decrease flood levels in the basins that were included in this study.

This study specifically updates the information from the 1998 and 1999 Englewood OSP Studies (Turner Collie & Braden).

The photos below illustrate the types of flooding experienced by the area included in this study. Thank you to the City of Englewood and Englewood citizens and businesses for providing images.

A metal footbridge is nearly submerged by fast-moving, muddy floodwater in a park, with trees and grass visible in the background.

A flooded park path with water covering the walkway, trees along the edge, and houses visible in the background at sunset. The wet pavement reflects the golden light from the sky.

A blue SUV drives through a flooded street, with muddy water swirling around its tires. Branches and debris are scattered along the edge, and floodwater covers most of the road.

Heavy rain floods a suburban street, with water covering the road and part of the front yard. Trees and a lamppost are visible, and the scene looks overcast and wet.

A flooded street next to a chain-link fence with a No Parking sign; debris and overgrown plants are visible near the fence, and water covers the ground up to the building.

Flooded alleyway next to a wooden building, with calm water reflecting the sky and nearby utility poles; pavement and a railing are visible beside the flooding.

A white van drives through deep, muddy floodwater on a street, with water splashing around its tires. A person is visible inside the van. Trees and grass are seen in the foreground.

Flooded residential street with several cars partially submerged in fast-moving water, surrounded by trees and grass, under an overcast sky.

A black car is partially submerged and driving through a flooded residential street, with strong currents of muddy water surrounding it and nearby houses and sheds in the background.

Flooded street with muddy brown water rapidly flowing over the pavement, reaching the edge of a grassy area. The current appears strong and turbulent.

Cars are partially submerged in a flooded street after heavy rain, with water covering the road and scattered hailstones on the grass and sidewalk in the foreground. Trees and houses are visible in the background.

A large rock sits in the middle of a flooded alleyway, with wooden fences on both sides. The water reflects the orange and pink hues of a cloudy sunset sky, creating a mirror-like surface.

Cars drive through a flooded street with brown water rising above the tires. A green street sign reads Dupont Street. Trees and grass line the road, and the sky is overcast.

A person walks on a grassy bank beside a swollen, misty river in a park, with trees and houses in the background under a cloudy sky.

Floodwaters cover a residential yard and street, nearly reaching a white house in the background. Trees stand in the deep, fast-moving water, and mist rises, suggesting ongoing heavy rainfall.

A muddy, flooded pond overflows onto a grassy area in a park, with trees and buildings in the background under a cloudy sky at dusk.

A flooded street with muddy water covers most of the road; cars are partially submerged, and only the roofs and tops are visible. Trees and a building are in the background, and a yellow traffic sign stands on the left.

Fast-moving brown water with visible ripples and waves, indicating a turbulent river or stream. The surface appears foamy in some areas, suggesting strong currents and recent rainfall or flooding.

Muddy floodwater flows across grassy ground, carrying debris and fallen leaves. The water creates ripples and waves as it moves, with some patches of grass partially submerged.

A backyard and driveway covered with patches of melting hail, puddles, and wet surfaces. A yellow garage sits on the left, a brown house in the background, and there’s a black fence along the right side.

A backyard patio covered in scattered hailstones, with patio furniture and childrens toys visible. The ground appears wet, and the sky is overcast, suggesting a recent hailstorm.

A backyard walkway and driveway are covered in a layer of white hailstones. A wooden fence lines the left side, and a brown brick house is on the right. The sky is overcast, and some hail is mixed with leaves.

A residential neighborhood is flooded, with water covering lawns and streets. A wooden fence is partly submerged, trash bins and toys float, and a children’s playset stands in the water near trees and houses.

A green metal chair sits partially sheltered beside a wooden wall, surrounded by floodwater and scattered debris after heavy rain. Trees and plants are visible in the background.

A backyard with green grass and landscaping sits behind a wooden fence, beyond which floodwater covers the ground and trees, indicating heavy rain and flooding.

A wooden fence stands on green grass near a flooded yard. Heavy rain falls, with bushes and trees surrounding a swollen river or creek in the background.

A car drives through a flooded street, causing a large splash. In the foreground, a wooden fence separates the street from a grassy yard with small apple trees. Rainwater has pooled in the yard.

Floodwater covers the ground between two houses and flows through an open wooden gate into a backyard, while a narrow sidewalk beside one house remains above the water.

A broken metal gate and a shattered screen door lie in muddy water beside a house, surrounded by debris, wet leaves, and damaged plants after flooding.

Two vehicles drive through a flooded street during heavy rain. A wooden fence and green lawn are in the foreground, with water flowing across the road and some hailstones scattered on the grass.

Floodwater fills a residential backyard and alley, with brown water flowing through an open wooden gate; heavy rain continues to fall, and trees and garages are visible in the background.

A wooden fence stands partially submerged in floodwater, with water covering the ground beyond the fence. Wet grass and plants are visible in the foreground, and tree trunks and a signpost appear in the background.

A backyard with a patchy green lawn, gravel, and concrete is covered in scattered hailstones after a storm. A wooden fence runs along one side, and a tan house is visible on the right.

A backyard with a small grill covered in hailstones, a chain-link fence, and patches of hail on the grass and ground. A yellow shed and brick buildings are visible in the background.

A pile of yard waste, branches, and debris, including a metal barrel and scattered trash, sits in front of a wooden fence on a dirt surface. Some overgrown weeds and yellow flowers are visible among the debris.

A blue SUV is partially submerged in deep floodwater on a street, with strong currents and a fallen tree branch nearby. Another vehicle is visible ahead, also affected by the flooding.

Heavy rain falling on a muddy surface, creating ripples and splashes across the waterlogged ground. The scene captures the texture of rain hitting the earth, with visible droplets and waves.

A flooded street with heavy rain and hail. Two parked cars are partially surrounded by water. A grassy yard with some hail accumulation is in the foreground, separated by a wooden fence. A green bush is near the sidewalk.

Rain pours down in a backyard, flooding the grass and parts of the patio. Wooden fencing, green bushes, and trees are visible, while the sky is gray and overcast, adding to the stormy atmosphere.

Goals

The main goal of this Study is to take the initial steps in planning for flood hazard reduction in Englewood. The Study takes a three-pronged approach to identify and mitigate areas of potential flooding at various rainfall/runoff levels:

Determine and define ways of reducing flood damage through floodproofing techniques.
Update the existing Outfall Systems Plan (OSP) and capital projects with budgets and a prioritized list of storm drainage projects.
Assess the current conditions of the stormwater pipeline beneath Oxford, identify causes of past failures and potential causes of future failures, and describe remediation techniques .

If you are a homeowner or citizen and you are interested in floodproofing your home or building, please click here to take you to the Floodproofing Study page.

Focus of the Study

This study answers three questions:

What can be done immediately to flood-proof homes in the affected areas?
What long-term regional storm drainage improvements can be implemented to eliminate or greatly reduce flooding?
What is the status of the Oxford Avenue storm sewer outfall and what can the City do to prevent future failures and/or sinkholes?

Various maps and graphics are presented within this site. This includes, but is not exclusive to, maps depicting flooding levels expected for a wide variety of storms, maps that depict proposed Capital Improvement Projects, maps that document citizen reported flooding, maps that demonstrate existing infrastructure, etc. Each map or graphic includes an explanation of its content.

Standards & Resources

Resources used in preparing this website:

Scope of the Study

This project utilizes basin delineation from the 1998/1999 OSP as show in the image below. As presented in the 1998/1999 OSP, this project focuses on the South Englewood Basin, South-Central Englewood Basin, Central Englewood Basin, Yale Avenue Basin, and North Englewood Basin, as shown in the image below.

This graphic shows the basin areas included in the subject study as defined and delineated in the 1998/1999 OSP. These basin areas were noted in the 1998/1999 OSP as “Probable Areas Affected by Flooding from the 100-Year Storm” (1998).

Flood Insurance

Flood Insurance is available to anyone, regardless of whether your property is within a delineated floodplain or not. All homes in or near the study area should consider the benefits of flood insurance. In addition to homes within these delineations, other homes are or may be subject to localized flooding. Therefore, even if your home is outside delineated flood limits or Areas of Probable Flooding, it may be advisable to consider insurance.

Up to $250,000 of structural coverage is available through the National Flood Insurance Program (NFIP). The 2018 rates can be downloaded using the link above.

Please see the FEMA NFIP website for more information.

The subject study was limited to the North Englewood Basin, Northeast Englewood Basin, Central Englewood Basin, South Central Englewood Basin, and South Englewood basin as delineated by the 1998/1999 OSP, as referenced herein. Citizens outside the limits of the subject areas should also consider Flood Insurance.

If you have any question about whether flood insurance is important for your home, please contact the City of Englewood Public Works Department or consult with a Professional Engineer (PE).

Scope of Services

Calibre worked with the City of Englewood to develop a Scope of Work (SOW) to address the basin areas of focus shown above and as defined by the 1998/1999 OSP. The work needed to be done quickly so that Englewood could proceed in addressing these known risks to residents. As such, the schedule of this project was shortened as much as possible, and the work done for this study built upon work that others had completed in the study watershed basin.

The final Scope of Work was as follows:

Life Safety Assessment and Floodproofing Report

Coordinate and meet with City
Provide project planning and project management
Conduct citizen outreach survey and one-on-one meetings
Conduct site visits and field recon for problem areas
Process data
Map flood concerns
Research floodproofing techniques (including, but not exclusive to, FEMA, USACE, City and County of Denver, City of Aurora, UDFCD)
Develop schematic-level details for floodproofing techniques
Provide cost estimates for floodproofing techniques
Conduct public meeting

Outfall Systems Plan Update & Capital Project Prioritization

Plot utilities
Prepare base map
Review existing studies
Review and determine flood depths at cross sections
Review existing proposed capital projects and analyze for flood hazard reduction
Update cost estimates for existing proposed capital projects
Perform hydrologic analysis and hydraulic analysis based on new data
Plot new limits of expected flooding
Compare flood hazard reduction via floodproofing with project costs
Develop prioritization schema
Evaluate pond locations (up to 5)
Evaluate existing projects

Pipe Conditions Assessment

Digital Report (Plan)