CIVIL 409 – GROUP ASSIGNMENT NO. 2

DRAINAGE SYSTEM DESIGN

CIVIL 409 ASSIGNMENT - Stormwater

(March 2025)

Master Drainage Plan

Develop a Master Drainage Plan (MDP) for a new development in South Surrey. Again, your group is a consulting engineering company and has been hired by a developer to develop a MDP.  The development area is shown in the attached Figure. You can use the City of Surrey’s COSMOS system to obtain the infrastructure information. You will be using the City of Surrey’s Design Criteria Manual as the basis of your design.  The plan should develop the conceptual layout to convey minor and major storm events, as well as identify the facilities and source control measures to protect the downstream aquatic habitat.  To do this, each group will need to complete the following:

Overview

Task No.1 – Source Controls: Select on-site source control measures to the capture lot and road surfaces to the “Volumetric Reduction Criteria”.  In this case, assume the volumetric reduction criteria is 72% of the 2-year, 24-hour rainfall.  Use the White Rock Rain Gauge in the City of Surrey’s Design Criteria Table 5.3.2 (non-climate change scenario).  Produce a plan drawing showing the location of the on-site control measures.  You can use schematic symbols to represent the source controls.  Produce additional drawings to show the typical sizing of both the lot and road source controls.  The developer should be able to relate the sizing shown to the  plan drawing to understand the scope of the source control measures.  Pick “typical” sizing for the lots based on an average lot size (pick one lot that is representative of  a single-family residential land use).   Pick “typical” sizing for roads based on the average road width of one representative street.   Assume that the streets will be grading to one side.  Determine the number of lineal metres of road source controls required to meet the volumetric reduction criteria.

Task No.2 – Storm Sewer Network: Develop and size a storm sewer network to convey the minor storms (5-year return period – non-climate change).  Use the rational formula to size the storm sewer.  Produce a table similar to Table 5.3.14 in the Surrey Design Criteria Manual (January 2016).  Show a plan drawing of the storm sewer showing manholes, pipes, diameters, contours, flow direction, and invert elevations (Note:  invert and ground elevations could be shown in a table as long as the manhole numbering is relatable).  Use the White Rock - Surrey IDF curve (non- climate change).

Task No.3 – Major Overland Flow and Pipe Network: Develop major overland flow routes and major storm collection trunks (100-year storm).  Show the direction offlow arrows on every street following the contours. Show sufficient arrows such that the reader can clearly understand where the major flows are going.  If the 100-year storm is to be picked up by a major storm trunk, show the connection and trunk sewer, and produce a separate plan drawing showing the additional tributary areas that are to be picked up.  Show where the major flow connects with the receiving water.  Include the 100-year design flows in the table described above. You do not need to develop flow values for the overland flows.  However, you do IF you add the 100-year flows to the 5-year storm network developed in Task 2.  Use  the 2050 Surrey White Rock (non-climate change scenario) noted above.

Task No. 4 – Detention Pond: Size a detention pond using the EPA SWMM5 model and design rainfall events in the Surrey Design Manual (January 2016).   Use the design criteria laid out in the Surrey Design Manual (January 2016) Section 5.2.1c.     Assume the “pre-development” 5-year flow rate is 0.006 cms/ha (6 L/s/ha).  You do not have to model the pre-development flow, just the post-development flow.

Assume that the source controls are fully implemented and functioning under the 5- year post-development flow (hint: you can assume that the rain gardens slow down  the runoff into the SWMM  model.  You can do this by doubling the overland flow length which is reducing the “width” parameter by 50%).   Use the Kwantlen Park Design Storms (Table 5.3.5) then pro-rate the values to match the White Rock rainfall station using factors that compare the two IDF curves (hint: Kwantlen park is in North Surrey, and it rains more in that part of the city).

Task No 5 – Cost Estimate: Develop a “Class D” Capital Cost estimate for your “Stormwater Management Plan”.  Add up all of the lengths of pipes, numbers of manholes, size of detention pond(s), extra land requirements for detention pond(s), number of lot-source controls, lineal metres of road source controls, and other drainage features and summarize in a table.  Use the unit costs attached to derive a cost estimate.  Note:  the attached costs assume that the land is undeveloped and do not include restoration costs.  For the purposes of this assignment, you do not have  to include other utility conflict costs or restoration costs.

Additional Details:

The following sections expand on the above tasks and list the deliverables expected. Task 1: On-site Drainage Measures (LIDs for frequent rainfall events)

Assume that the entire area is zoned single family residential, and that each lot will have its roof leaders disconnected (with the exception of the school and parks).  Assume that each road will be serviced by rain gardens (ie. A vegetated swale),, but the maximum distance water can travel in a swale is 1 city block before it is picked up by the minor drainage system (Task No.2).  Assume that the post-development infiltration rate of the soil is 1.5 mm/hour.

You need to calculate the topsoil depth of a ‘typical’ lot to hold and infiltrate the volumetric control criteria. The depth should be sufficient to capture the rainfall that falls on the front and back yards plus the diverted water from the impervious areas including the roof, and a 4 metre wide driveway.  Use the Simplified Rainfall Capture Method to calculate the depth required (see lecture notes). Include the lawn in the front boulevard within the City’s right of way, but  not the paved portion of the road (see next bullet).  You may need more than one typical lot based on size, but do not exceed three.  Assume that a typical house footprint, deck, and driveway occupies 65 % ofthe lot (65% impervious). Include a rock pit if necessary to increase the storage required.  The zoning is “RF” (single family residential with 3.6 people per household).

You need to calculate the width, soil depth, and rock storage volume required to design the rain gardens.  Again, use Simplified Rainfall Capture Method to do this.  Calculate the average road width based on the roads in the study area, as long (8.5m wide minimum).

Not all of the street will be able to have a linear rain garden on one side.  There will be driveways and other obstacles taking up space.  Calculate the % of the road that could accept a rain garden then enlarge the rain garden width to accept the additional street area.  For example, if 50% of the road length is occupied by driveways, you will need to have twice the pavement tributary to each lineal metre of rain garden.

Task 2: Minor Drainage System (5-year storm)

Deliverables:

a figure showing the storm sewers, manholes, and catch basins required to convey the 5-year design storm;

a table showing the design flow calculations for each pipe, selected pipe size, proposed inverts, ground elevation, and resulting capacity (similar to Table 5.3.14);

Task 3: Major drainage system (100-year storm)

Deliverables:

a figure showing the flow paths (arrows) of the stormwater during a major 100- year storm event.  The flow paths should demonstrate the water can adequately be conveyed to a creek system (drainage outlet) without flooding downstream properties.  If this is not possible, the minor drainage system will have to be upsized in that particular area to accommodate the 100-year flows.

An additional table showing the design calculations of any upgraded storm sewers required to pass the additional 100-year storm.

If portions ofthe storm sewer network are to be used to pick up the 100-year storm, produce a plan view drawing showing the additional tributary areas.

Note: if it is possible to safely convey the 100-year storm overland without flooding any properties, you do not have to calculate the 100-year flows in those areas, but show the drainage path and note it’s purpose.

Task 4: Detention Pond Design (Erosion Protection)

Deliverables:

A figure showing the setup of the EPA SWMM5 computer model (ie. Tributary area(s), node numbers, and pipe numbers)

A figure showing the location and size of the proposed detention pond(s).  The figure should include the additional piping required to route flows from the storm sewer collection system to the pond.

The maximum pre-development flow rate should be 6 L/s/hectare.  This is the maximum release rate that can be allowed into the creek system for storms with a five-year return period.

The detention pond should be sized to attenuate the developed portions ofthe study area.  You should show the tributary area of the pond design if it differs   from the study area.

A time-series graph showing the proposed 5-year, post-development input flows over 24-hours, proposed outlet flows (based on the orifice equation), comparison with the pre-development flow rate, and resulting incremental storage volume.  The graph should have time on the x-axis, flow on the primary y-axis, accumulated storage on the secondary y-axis.

Hint:  don’t do the pond sizing analysis in the model.  Export the hydrographs to a spreadsheet and do the analysis in the spreadsheet.

Task 5: Costing and Summary Report

Develop a Class D cost estimate table showing all of the capital items.  Use the cost table attached as a template for your estimate.

Summarize your findings into a brief report incorporating the above tables and figures.

Costing Information

Source Control Costs:

Rain garden for Road-side Source Controls - $500 / lineal metre

Soil Costs for lots – ignore

Rock Pits for Lots - $350 / cu.m

Piping and lawn basins for rock pits - $2,500 / lot

Pipe Costs (by diameter):

200 mm - $ 175/ lineal metre

250 mm - $ 190/ lineal metre

300 mm - $ 2100/ lineal metre

350 mm - $ 215/ lineal metre

450 mm - $ 230/ lineal metre

600 mm - $ 290/ lineal metre

750 mm - $310 / lineal metre

900 mm - $ 320 / lineal metre

Manhole costs:

$4,000 / manhole (1050 mm dia.)

Catch Basin Cost:

$ 2,250/ standard catch basin (5-year flow)

$ 3,500/ side inlet catch basin (100-year flow)

Property Costs for Detention Ponds:

Within road right-of-ways – no charge

Within Parks - $ 3,000,000/ha

Occupying Lots - $8,600,000 / ha

Detention Pond Costs:

$ 100.00/ cu. metre excavation or berm construction

inlet structure – assume $25,000

outlet structure – assume $50,000

Detention Pond Design

Criteria

You are only sizing the detention pond for rate control of the 5-year storm.  It is assumed that with the source controls installed, the 2-year storm is adequately  mitigated.  For this assignment, the larger storms do not have to be analyzed.

Design Storm – 5-year, run the 2-hour, 6-hour, 12-hour, 24-hour durations (use Kwantlan Park Station – Table 5.3.5 but pro-rate as discussed above)

Maximum depth – 1.5 m

Side Slopes – 2:1

Release rate – 6 litres/second/ha

Use orifice and or weir equation provided in City of Surrey Design Criteria

Manual (January 2016).  Remember orifice flow rate changes with increasing

deoth (Section 5.4.7.2).  Pick a combination that optimizes the pond size but still meets the criteria.

Standard Pipe Diameters