Drainage and Hydrology Engineering
Our team is experienced in all aspects of storm drainage design and floodplain management.

Services Include:
(see below for representative projects)

Master
Drainage
​Studies
Hydrology
and
Hydraulics
Evaluation of
Existing
​Drainage Systems
Storm Drainage
System
​Design
Detention Storage
Design and
​Analysis
Floodplain and
Drainageway
​Modeling
Conditional Letter
of Map Revision
(CLOMR)
Letter of
Map Revision
(LOMR)
No-Rise
Certification
​
Grading, Erosion and 
Sediment Control
​(GESC)
Stormwater
Treatment and
​Management
Development 
​Review
​

Contact:

​​Ricardo J.F. Goncalves, ​P.E.

PRESIDENT
​
Direct Line: 303-468-8484
Cell: 303-901-2367
[email protected]


Gary E. Welp, ​P.E., CFM

SENIOR PROJECT MANAGER
​
Direct Line: 303-468-8484
Cell: 303-901-2447
[email protected]

Representative Projects
(Click to Open)

Drainage and Hydrology Engineering

Castle Rock Development Company, Castle Rock, Colorado
Meadows Town Center​

This project included approximately 420 single-family and 2,402 multi-family dwelling units with 23 acres of commercial development.  RGA provided engineering services for all civil design from sketch plan through construction document approval.  Design challenges included balancing earth work activities over 1,200,000 cubic yards of material, connection of major infrastructure utilities through the property and incorporating a meandering drainageway.  Drainage improvements included piping the 100-year upstream contributions through the property.  
​

Castle Rock Development Company, Castle Rock, Colorado
Meadows Filing No. 20

The RGA team prepared a Final Drainage Report for 298 acres and approximately 420 single-family and 2,400 multi-family homes. The development included a regional drainage system comprised of central riparian drainage channel corridor between two (2) regional ponds that are approximately 49 acre-feet in size.

Castle Rock Development Company, Castle Rock, Colorado
Meadows Filing No. 20 - Regional Detention Pond

RGA prepared modification plans for the outlet structure and regional detention pond to bring it into conformance with existing criteria. The modifications involved included the installation of the boulder wall forebay, concrete water quality structure and concrete sedimentation basin.

Castle Rock Development Company, Castle Rock, Colorado
Meadows Filing No. 20 - Phase IB

​RGA designed and prepared plans for a 2.78-acre 137 units as a part of cluster home community. 

Castle Rock Development Company, Castle Rock, Colorado
Meadows Filing No. 20, Phase 2, Area 2, Plat Amendment 7, Oakwood Cluster West

RGA assisted the Castle Rock Development Company with the re-plat and re-design of the Meadows Filing No. 20 “Eyebrows” off of North Meadows Drive for a single family residential Cluster Unit Development. RGA created a site development plan, construction plans, grading, erosion and sediment control (GESC) plans, Phase II Drainage Study Addendum, utility report addendum, and phasing plan.

Castle Rock Development Company, Castle Rock, Colorado
Meadows Filing No. 20, Parcel D & E

RGA completed subdivision design for 50 lot single-family development. 

City of Boulder, Colorado
US Highway 26 and Boulder Road Bikeway

The RGA team provided the design of approximately 1,000 LF of a concrete bikeway connector along U.S. 36 and Baseline Road in conjunction with highway and ramp widening. Work included profiles, design of an underpass under the on-ramp to U.S. 36, extensive rock retaining walls, storm sewer and irrigation ditch bypass, local drainage and coordination with CDOT Region IV. 

City of Littleton, Colorado
On-Call Engineering Services

RGA provides on-call services to the City of Littleton Public Works Department for development review services. Services include, but are not limited to the review of drainage reports, review of site development plans, review of subdivision exemptions, review of stormwater management plans, review of construction plans, review of erosion control plans, preparation of comment letters and PDF redline comments, attend meetings or site visits with applicants or their engineers (as-needed), and perform construction and stormwater site inspection/site visits.

City of Sheridan, Colorado
Drainage Enterprise Rate Study

The RGA team performed a study to determine a drainage monthly fee rate that would pay for on-going operational expenses and future capital improvements. The rate included a base fee plus a fee based on the percentage of impervious surfaces contained on the property.

Clear Creek County, Colorado
On-Call Engineering and Planning Services

RGA provided on-call engineering and planning services to the Community Development Department related to development, driveway, excavation, and floodplain applications. This included review of construction drawings, drainage reports, transportation, impact reports, and other similar documents associated with land development projects to ensure compliance with regulations and conditions for approval. This also included review of plans and reports, verify compliance with regulations, and administer BMP’s, driveway, grading, drainage and stormwater management, retaining walls, and floodplain development permits. We also completed site inspections to confirm BMPs and compliance to approval site plans. RGA also assisted the county with an update to their site development and grading standards.

Colorado Amateur Motor Sports Association, Arapahoe County, Colorado
High Plains Raceway

RGA prepared preliminary development plans, final development plans and drainage reports for the revitalization of the Interstate Kennel Club dog racing facility into a facility for motor sports, concerts and events. In addition, RGA designed the permanent water and sanitary sewer treatment facilities to modernize the dated infrastructure.

Colorado Technology Center Metropolitan District
Dillon Road and 104th Street Improvements

This roadway rehabilitation and improvement project that amounted to more than $2,200,000 and consisted of approximately 4,000 LF of roadway and 4,500 LF or curb, gutter, and sidewalk.  The project required the construction of a portion of Urban Drainage Flood Control District Drainageway G, adjacent to this site, and consisted of 5,000 LF of drainageway channel, two major culvert crossings, and three grouted boulder drop structures.  The RGA team provided the design and construction administration for the project and coordinated the approvals with the City of Louisville, Urban Drainage Flood Control District, concurrent lift station design, and various utility companies. 

David Hubbard, Douglas County, Colorado
Legends Club Subdivision

The RGA team provided design and grading layout for a minor development with four single-family home lots. We provided Construction Drawings, a Phase III Drainage Report, Grading, Erosion, and Sediment Control Report and plans and assisted with coordination with Douglas County.

Deer Creek Metropolitan District, Jefferson County, Colorado
Massey Draw Drainageway Improvements

Drainageway improvements to Massey Draw were required to repair major erosion and protect existing trail crossings.  The project consisted of grouted, stacked boulder armorment of the trail embankment and a grouted boulder drop structure with creative channel bank treatment and stabilizing channel head cutting protection.  This project involved review and permitting through Jefferson County Planning and Engineering, Federal Emergency Management Association, and the Urban Drainage Flood Control District.

Highlands Ranch, Douglas County, Colorado
Highlands Ranch Filing No. 118, 119L, 118K and 13

​The RGA team prepared the final drainage studies for approximately 5,000 single-family lots, including inlet and storm sewer sizing and design, as well as sizing of major drainageway culverts. 

Kings Point Development Company, Arapahoe County, Colorado
Kings Point Filing No. 2 and No. 4

RGA provided the design for 353 units on approximately 224 acres including the preparation of a contextual site plan, final plat, construction drawings, streets, water distribution, sanitary sewer collection, storm sewer systems and drainage way improvements.

Lennar Homes, Castle Rock, Colorado
Red Hawk Filing No. 3, Phase 5

RGA assisted Lennar Homes with drainage, utility, and traffic conformance letters, updated construction plans, GESC report and GESC plans for the development of Phase 5 within Red Hawk Filing No. 3. RGA also assisted with the original work in 2005, which consisted of a Final Drainage Report for 103 acres and approximately 193 single-family and multi-family homes. The development includes a regional drainage system comprised of storm sewer and five detention ponds.

Lennar Homes, Castle Rock, Colorado
Red Hawk Filing No. 3

The RGA team prepared plats and final construction drawings for this 195-lot single-family detached subdivision. The project included several difficult aspects such as encroachment on a Town-owned golf course, application for Federal Emergency Management Association floodplain revision, mountainous terrain, and extensive coordination with adjacent developments for utility connections and design of interconnecting roadways. 

Lincoln Park Metropolitan District, Douglas County, Colorado
Infrastructure Rate Study

The RGA team analyzed increasing costs of operations and maintenance of the roadways and drainage systems, developed a computer model, and made recommendations to the board as to how fees and charges needed to be increased in order to get the district to “operate in the black.” 

Parker Water and Sanitation District, Parker, Colorado
20 Mile Road Raw Water and Reclaimed Water Lines Phase I, II, III and IV

The RGA team provided design, construction management, observation, and administration for reclaimed water and raw waterlines consisting of 23,000 LF of 16-inch pipe, 3,000 of 24-inch pipe and 2,000 of 12-inch pipe.  This series of projects also included: 11,600 LF of dual 16-inch PVC effluent and 5,500 LF of 24-inch, 16-inch and 12-inch PVC raw water lines, including 600 LF of 54-inch diameter tunneling and casing under existing streets. 

Parker Water and Sanitation District, Parker, Colorado
Cherry Creek Diversion Structure

The RGA team designed a structure on Cherry Creek to divert water to a pump station supplying the Rueter-Hess Reservoir. The final structure has a wide foundation constructed perpendicular to the flow of Cherry Creek with retaining walls along each bank. The project utilized 2,340 CY of reinforced concrete and required a major dewatering effort. The RGA team also completed all construction management and administration for the project. 

Parker Water and Sanitation District, Parker, Colorado
Clarke Farms Lift Station

RGA staff provided inspection and contract administration for this 3,000 GPM lift station with the ability to serve 1,400 homes. The RGA team provided site drainage and detention requirement for site layout.

Patricia and Jim McCully, Weld County, Colorado
McCully/Schell Boulder Creek Floodplain

This improvement project included the placement of a boulder retaining wall to protect a lake/rail rights-of-way along and within the Boulder Creek floodplain.  The design involved mapping the floodplain and floodway for approximately a mile and a half of Boulder Creek in an area that had previously only been designated as an approximate floodplain with no floodway.  The modeling incorporated a roadway/bridge crossing, an old railroad embankment, several temporary gravel stock piles and excavated gravel pits.  This project included review and approval of HEC-RAS modeling and project design through Weld County, Federal Emergency Management Association and the Town of Fredrick.

Stonegate Village Metropolitan District, Douglas County, Colorado
Chambers Road Extension

The RGA team provided the design and construction management for the extension of approximately 1,300 LF of Chambers Road from Lincoln Avenue to a new high school.  Chambers Road is a 4-lane arterial street, and the project included the design of a full signalized intersection with acceleration/deceleration and left turn lanes at the intersection of Chambers Road and Lincoln Avenue.  Lincoln Avenue is a 4-lane major arterial street.  The project included the extension of 60” drainage culverts, inlets, and a 24” storm drain system.  The outlet system required Urban Drainage Flood Control District review and approval.  The project required coordination and approval by Douglas County.

Town of Buena Vista, Colorado
Town Engineer

RGA was the Town Engineer for this Colorado town for seven years, and now is staff support providing on-call services. We have performed planning, design and construction administration for street rehabilitation, streetscape, drainage studies, drainage facilities, trails, water line replacement and extensions, sewer lift station, water master plan and rate studies, and other miscellaneous projects. We also provide development review and referral agency management to the town.

Town of Buena Vista, Colorado
Roadway and Drainage Improvements and Drainage Master Plan

RGA developed the Town’s drainage master plan, which directs and dictates numerous smaller facilities such as tree lawns, infiltration galleries, roadside ditch controlled containment, use of baseball and sport fields for detention and water quality infiltration, instead of a one-size-fits-all regional facility. This approach uses a green storm water infrastructure and local water quality capture-in-place of large pipe systems and discharges to the Arkansas River as fast as possible, which allows using the storm water runoff by the town to supplement irrigation.

Town of Estes Park, Colorado
Bond Park Phase I and III

RGA provided the engineering design for storm sewer, channelization and infiltration system to eliminate existing drainage problems; replacing asphalt; incorporating parking delineation in decorative stone pattern to eliminate typical painted stripes; eliminating curb and gutter; rock boulder bollards; and flowing curvilinear roadway, sidewalks and planter beds. This project included roadway, drainage, landscape, and streetscape improvements. The work included Macgregor Drive which is directly west of Town Hall. RGA and Winston Associates worked closely with the Stakeholder Committee and Town Staff to complete a detailed design for Phases I and III that was on time, within budget, functional, high-quality, and integrates seamlessly with Estes Parks’ downtown.

Town of Estes Park, Colorado
Master Drainage Plan

RGA developed the Estes Park Drainage Master Plan, which provides an overall guidance plan for the regionalized study areas to aid in the planning of future actions and improvements. The Plan coordinates the use of open spaces, rights of way, drainage tracts and easements in order to recommend environmentally conscious hydraulic design to remedy existing problems and/or areas where problems may be incurred. The study area is 1,400 acres and takes into account planning for open spaces, transportation, water quality, water storage, flood plain mitigation, wildlife and other emerging urban/commercial considerations. RGA provided study analysis and design and coordinated the approvals with the Town of Estes Park and Larimer County.

Town of Jamestown, Colorado
​James Creek Irrigation Ditch

The RGA team performed engineering design and provided construction management services for the replacement of portions of James Creek Irrigation Ditch that were destroyed during the 2013 floods. This work consisted of preparing construction documents, advertising for bids, and assisting with the award of contracts.

Town of Jamestown, Colorado
No-Rise Certification

The RGA team assisted with the preparation of a No-Rise Certificate for the base flood elevation in the Town Square Park. The determination was based upon Manning cross-sectional determination utilizing three cross-sections with the property as a basis. RGA also assisted with the design and construction management of the 2013 flood destroyed Town Square Park. 

Town of Nederland, Colorado
September 2013 Flood Repair Project

This project consists of 7 separate repair areas, work included replacements for roadways, culverts, repairs to road surface, swales, and slope and bank stabilization. RGA is familiar with the latest versions Colorado Department of Transportation (CDOT) Local Agency Manual, CDOT Construction Manual, CDOT Field Materials Manual and the procedures associated with maintaining compliance for FHWA, Federal Emergency Management Association and CDOT funded projects.  

Town of Nederland, Colorado
Community Center Generator

RGA assisted with design and construction management of a new generator to mitigate flood damage at an emergency evacuation center. 

Town of Parker, Colorado and Urban Drainage and Flood Control District
Sulphur Gulch Channel Improvements - Phase II

Severe erosion along the banks of Sulphur Gulch exposed abandoned irrigation lines and caused the collapse of a portion of the pedestrian trail, as well as damage to the embankment of the Bar CCC reclaimed water pond.  The RGA team acted as design engineer and construction manager for the channel improvements, which included a sculpted concrete drop structure, a grouted riprap grade control structure, and buried riprap channel revetment to increase channel stability. The improvements resulted in a lower water surface elevation during the 10-year storm event. The project also required habitat restoration, wetlands mitigation, and protection of the regional trail system. RGA designed 850 LF of channel improvements along Sulphur Gulch adjacent to the Bar CCC Park. The project involved evaluation of the alignment, approvals from federal, state and local agencies, and construction management. Channel improvements included a sculptured concrete drop structure, grouted riprap grade control structure and buried riprap channel revetment. Design parameters included design coordination with existing bridge abutments and piers, the connection and re-alignment of the Town of Parker Regional Trail System, access from the Bar CCC parking area, and the synchronization with the existing Parker Water and Sanitation District mixing station and associates outfall/channel improvements to Sulphur Gulch at the termination of this project.

Town of Parker, Colorado and Urban Drainage and Flood Control District
Longs Way Tributary Improvements

RGA provided the design and construction management for the installation of two (2) regional detention ponds.  The regional facility improvements consist of two detention ponds, 600-feet of storm sewer, and a connection structure to the existing Town of Parker drainage system.  The detention ponds provide 6.0 acre-feet of storage and 1.2 acre-feet of water quality treatment.  

Town of Parker, Colorado and Urban Drainage and Flood Control District
20-Mile Regional Storm Water Facility

RGA designed two (2) cell inter-connected regional detention ponds along Plaza Drive adjacent to Cherry Creek.  The project involved evaluation of the alignment and hydraulics, approvals from federal, state and local agencies, and construction management. The project included the installation of a 40.5 acre-feet regional detention facility.  The basin analysis for the 395 tributary acres was modeled using CUHP and SWMM hydrology for the existing and proposed land uses as dictated by the Newlin & Baldwin Gulches and Basin 4600-09 Outfall System Planning Study.  The facility consisted of hydraulically connected dual detention ponds with sediment collection cells and 10.0 acre-feet of controlled release water quality storage. The design also included box culverts and a 54-inch storm sewer system.  The 570 cubic-feet per second released into an environmentally sensitive area of Cherry Creek from the detention facility is controlled by a concrete multi-staged weir and a grouted sloping boulder drop structure.

United Asphalt, Commerce City, Colorado
HEC-RAS Analysis

​RGA prepared a HEC-RAS analysis of Sand Creek to determine the impacts of fill placed south of United Asphalt’s location and west along Sand Creek trail. Utilizing this analysis, we provided a revised preliminary floodplain, analysis of the addition of a flood wall, and a comparison to the existing floodplain for the client’s submittal to Commerce City.