STORMWATER

The firm provides a complement of planning and design services, from conceptual and preliminary design through final design, construction plans, specifications and estimates, contract administration, bidding services, construction coordination and observation services, and close-out.


Cherry Creek Restoration

 

Muller has worked on many projects along Cherry Creek in the Denver area. Work began with a series of studies including:

  • Cherry Creek Basin Open Space Conservation and Stewardship Plan for the Trust for Public Lands.
  • Cherry Creek Watershed Plan 2003 for the Cherry Creek Basin Water Quality Authority (CCBWQA).
  • Cherry Creek Corridor Restoration Study for the Town of Parker.

These studies discussed the importance that stream restoration has on water quality protection and wildlife habitat and made a strong case for mitigating degradation in Cherry Creek to restore the healthy functions of the corridor.

Muller has further developed the approaches recommended in these three studies during the design and construction of eight stream rehabilitation projects along upper Cherry Creek, shown in the figure and described on the next page.

  • Cherry Creek d/s of Arapahoe Road (1)
    Length: 5,000’
  • Arapahoe Road Bridge and Cherry Creek Restoration Project (2)
    Length: 2,000’
  • Cherry Creek at Eco Park (3)
    Length: 4,900’
  • Cherry Creek at 17-Mile House Project (4)
    Length: 2,500’
    This project won the 2007 Grand Award for Engineering Excellence from the Colorado Association of Stormwater and Floodplain Managers
  • Pine Lane Bridge and Cherry Creek Restoration Project (5)
    Length: 1,200’
    This project won the 2007 APWA Project of the Year Award – Utility, Drainage and Environmental for Medium Communities Category.
  • Cherry Creek at Main Street Restoration Project (6)
    Length: 5,000’
  • Hess Road Bridge and Cherry Creek Restoration Project (7)
    Length: 2,500’
  • Cherry Creek at Stroh Ranch Restoration Project (8)
    Length: 5,000’

All of these projects have taken a holistic approach to heal the degraded creek corridor, not only stabilizing the channel, but restoring the natural hydrology, water quality benefits, and habitat value of the corridor. The projects have used riffle drops and other grade control structures to raise and re-establish the baseflow water surface close to the adjacent vegetated benches of the primary channel, keeping the water table high to help sustain riparian vegetation, promoting wide, shallow flow conditions during high flow events, and keeping velocities low and infiltration into the sandy alluvium high. Historic secondary channels have been re-established, tributary channels have been enhanced, water quality detention has been provided to treat inflowing runoff, banks have been protected using bioengineering approaches, and trail connections and crossings have been created.

   

17-Mile House 17-Mile House

 

 

 

 

 

Rehabilitation Projects Along Upper Cherry Creek Rehabilitation Projects Along Upper Cherry Creek

Before Before

After After

Before Before

After After

 

COTTONWOOD CREEK

 

In response to increased runoff from urbanization, Cottonwood Creek upstream of Cherry Creek Reservoir began to experience severe degradation and bank erosion. Within Cherry Creek State Park, the channel had downcut up to 10-feet and had become disconnected from its historic floodplain. The downcutting lowered the water table, resulting in a corridor that was largely devoid of riparian vegetation. The eroded soils, along with other pollutants such as phosphorus, were being carried into the Reservoir, degrading its water quality. A project was initiated to stabilize the creek and reduce the inflow of sediment and phosphorus into the Reservoir.

Muller’s proposed improvements went beyond simply stabilizing the creek in-place. The approach involved raising and restoring the creek to re-create a shallow, meandering stream that is reconnected to a broad, well-vegetated floodplain. In addition, the water table was raised to create hydrologic conditions that are conducive to regenerating cottonwoods, willow, and other riparian species along the channel edges and broader floodplain. The first phase of improvements was constructed in 2003/2004 and was the first project in the Denver metro area to use “riffle drops” for grade control. The riffles were constructed of a special rock mix that Muller pioneered called “void-filled riprap” that consists of a well graded matrix of rock, cobbles, gravels, and sands to emulate natural riffle material. The design also included restoring meanders in the active channel and providing periodic wetland pools for habitat diversity and improved water quality treatment. Bioengineering approaches for stabilizing banks were implemented and included a combination of willow fascines/stakes, rock toe protection, and preformed scour holes. The second phase of stream improvements was constructed in 2009 and, in addition to riffle drops, included several rock chute grade control structures.

In addition to stream restoration, Muller also designed an online pond on Cottonwood Creek at Peoria Street. The pond provides flood protection and water quality benefits for Cherry Creek State Park and Cherry Creek Reservoir through a sediment basin, wetlands and water quality capture volume. A triple box culvert allows 100-year flows under Peoria Street and accommodates a trail crossing for horse, bike rider, and pedestrian access to the Cherry Creek Park Open Space. Upstream of the box culvert, is a water quality pond. Also included is a meandering wetland channel to further clean the water before it is discharged.

   

Before Before

 

Cottonwood Creek Reclamation Plan Cottonwood Creek Reclamation Pond

 

 

 

 

 

 

 

 

Peoria Street Pond Peoria Street Pond

 

Stormwater Improvements for the
RTD FasTracks West Rail Line 

 

The West Rail Line is the first of six new segments of Light Rail Transit to be designed and constructed under the Regional Transportation District (RTD) FasTracks Program in the Denver Metro Area. The West Rail Line stretches 12.1 miles from the Auraria Campus in downtown Denver to the Jefferson County Government Center in Golden, and has a total project cost in excess of $700 million. As the Stormwater subconsultant for the project, Muller Engineering collaborated with prime consultant David Evans & Associates, contractor Denver Transit Construction Group, and numerous other subconsultants over a seven-year design and construction period. Muller’s scope of work included design of a wide range of improvements including:

  • floodplain modeling including a CLOMR and LOMR
  • 2.5 miles of major drainageway improvements
  • 7 drop structures
  • 9 major drainageway cross culverts
  • 36 Urban Drainage and Flood Control District maintenance-eligible outfalls
  • local drainage facilities for the entire corridor and adjacent roadway improvements
  • trackway drainage
  • 2,000 lineal foot box culvert that reduces the 100-year floodplain and took nearly 30 structures out of the floodplain
  • detention and/or water quality for 3 Park-n-Ride stations and major roadways
  • a water quality assessment for the ballasted trackway
  • irrigation ditch facilities
   

 

Dry Gulch drop structure Dry Gulch drop structure
Aerial courtesy of David Mallory

Lakewood Gulch Lakewood Gulch

 

Urban Drainage / Floodplain Projects

 
Sable Ditch Detention and Water Quality Pond

This 8.5 acre pond in Aurora, Colorado reduces flood flows so that they can be accommodated in an existing downstream channel. The design was complicated by a shallow gradient sanitary sewer that had to be re-located around the pond and through the middle of the pond outlet structure. The pond was designed for 100-year flood storage and also water quality treatment of the Excess Urban Runoff Volume (EURV). A large inlet captures 100-year flows and conveys them into a reinforced concrete box that leads to the pond. Muller provided construction management of this complex project and prepared all documentation for a FEMA floodplain revision that removed many structures from the floodplain.

Left Hand Creek

A complex hydraulic system in Longmont, Colorado with eleven flow splits and 211 structures within the regulatory 100-year floodplain was analyzed. Improvements designed to take 172 structures out of the 100-year floodplain consist of two pedestrian bridges, an enlarged box culvert crossing at Main Street, an enlarged culvert at South Pratt Parkway, roadway modifications at Pike Road, and a continuous trail system.

Lakewood Gulch

Lakewood Gulch at Dudley Street in Lakewood, Colorado is typical of many of the urban drainageway projects that Muller is involved in. Increased flows from urbanization lead to downcutting of this urban channel, causing steep -- sometimes vertical -- banks that frequently collapse. These collapsing banks erode into adjacent private properties, fences, and other infrastructure. Many times the surrounding development did not adequately account for the drainageway and its floodplain and as a result, there was very limited space to work with.

   

Sable Ditch Pond Sable Ditch Pond

Left Hand Creek Floodplains Left Hand Creek Floodplains

Lakewood Gulch - Before
Lakewood Gulch - Before

Lakewood Gulch - After
Lakewood Gulch - After

 

Innovations in Drop Structure Design

Muller has been an industry leader in developing innovative drop structures for stream restoration projects. Drop structures are often necessary in urban settings, to flatten the overall gradient of a stream, reduce flow velocities and halt vertical incision. Below are some examples of Muller’s drops:
 

Colored sculpted-concrete. These drops are made to look like natural outcrops of sedimentary rock. Photo from Grange Hall Creek

 

 

 


Soil –cement. These drops also appear like sedimentary rock outcrops
Photo from Shop Creek

 

 


 

Riffle Drops. These small drop features are made of a mixture of riprap, rounded cobbles, and aggregates, and mimic the riffles found in natural pool-riffle sequences.
Photo from Cottonwood Creek

 

 

 

Glass-Fiber-Reinforced Concrete. These drop structures mimic rock outcroppings to create a “waterfall” appearance. The structures are made from panels that facilitate more vertical faces.
Photo from Lakewood Country Club.

 

Colored-sculpted concrete Colored-sculpted concrete

Soil-cement Soil-cement

Riffle Drops Riffle Drops

Glass-Fiber-Reinforced Concrete Glass-Fiber-Reinforced Concrete

 

777 S. Wadsworth Boulevard, Suite 4-100, Lakewood, CO  |  303-988-4939  |  © Muller Engineering Co., Inc.  |  Site Map