April 2024
editionWater space under the ground
Plastic material for water storage

CROSS-WAVE

SEKISUI CHEMICAL CO., LTD.

CROSS-WAVE Overview※ As of March 2024

Cumulative total pondage in Japan

More than

3.3
26
14,00097％

Reliable track record

Cumulative total installation in Japan

Over

More thanmillion m³

years
from release

Prefecture penetration rate

cases

Plastic material for water storage required now

The CROSS-WAVE series is intended to construct rainwater storage and inﬁltration reservoirs by burying
plastic blocks(made of recycled polypropylene resin) under the ground in order to reduce rainwater
runoﬀ and use rainwater. Piling up blocks so that they intersect at right angles achieves a high void ratio,
securing necessary and suﬃcient pondage. The completed structure is signiﬁcantly stable.
SEKISUI CHEMICAL CO., LTD. launched the CROSS-WAVE series in 1998. Since then, it has been adopted
at both public and private facilities, and the cumulative total of installation and the cumulative total
pondage have exceeded 14,000 cases and 3,300,000 m³, respectively. Also, the prefecture penetration
rate has reached 97%. As a manufacturer of plastic storage materials, we have the best track record inJapan and continue to steadily increase the number of installation cases also in overseas countries.
Furthermore, we provide high-quality products by producing them at our own plants.

Obtained technology
assessment certiﬁcationfrom the Association
for Rainwater Storage
and Inﬁltration

Obtained certiﬁcation for
new technology research resultsfrom the Japan Institute of
Wastewater Engineeringand Technology■ Use applications of CROSS-WAVE

2

Even in the event of heavy rain due to typhoons andtorrential rain, rainwater can be stored under the groundeﬃciently and safely to reduce rainfall runoﬀ, minimizing
damage from ﬂooding.

Rainwater use

Rainwater runoﬀ
reduction

Materials for rainwater storage provided by a leading
plastic manufacturer, Sekisui, for control of ﬂooding due
to typhoons, torrential rain, etc.
Stored rainwater
can be used as:
Household nonpotable waterIndustrial water
Agriculturalwater

■ Five features of CROSS-WAVE

5

1
Void ratio

Environmental
friendliness

Achieving a 95% void ratio
allows storage of substantial
volume of water

The use of recycledmaterials reduces
environmental impact

4

2

Load
capacity

3
Resistance against

Easy
installation

Use ofrecycled plastic

earthquakes

Can load a T-25 truck(Except for general roads)

No ﬁxing material requiredand can be installed manually

Resistant to level-2 seismic movements
No collapse even in the event of
the Great East Japan Earthquake

Rotating
90 degrees
Rotating
90 degrees

By piling up corrugated plastic
blocks so that they intersect atright angles with each other(requiring no jointing materials),a robust and rigid structure canbe constructed while securing
great voids between blocks.

Since CROSS-WAVE is fully buried under the ground to store
rainwater, rainwater storage and inﬁltration measures can betaken without impairing the scenery around the facility andin the community.

SEKISUI CHEMICAL CO., LTD. aims to produce
products for achieving SDGs※ through
CROSS-WAVE.

Six SDGs that CROSS-WAVE is aimed at achieving. Through initiatives to achievethese goals, Sekisui Techno Molding has declared to return more natural capitalback to the planet than it uses to help to conserve the natural environment.

※ Internationally shared goals from 2016 to 2030 speciﬁed in the 2030 Agenda for
Sustainable Development, adopted at the United Nations Summit held in September 20153

Product Lineup

Broad product lineup according to the purpose
Proposing the most suitable product for every environment
We oﬀer four types of products with diﬀerent earth covering and burial depth that respond to various

installation conditions and burial environments of each customerʼs desired rainwater storage and inﬁltration
facility. We will propose the optimum product for each customer. Please do not hesitate to contact us.

■ Product selection guide table
Maximum
burial depth

Product

2.8m max.

CW-HD

0.5m〜

0.6m〜

0.8m〜1.3m

〜1.6m

〜2.0m

〜2.2m

CW-S

Under 4.0m

4.0 to 6.0m

Earth covering

CW-Ne
CW-NS

（For under 4.0m,
CW-Ne is used.）

Note 1) In the case in which the speciﬁc weight of soil is 18 kN/m³
Note 2) In the case in which a live load (when a T-25 truck passes) is considered

4 types of products cover a wide range of
purposes and conditions.

CW-HD

CROSS-WAVE HD
Product nameDimension (mm)
Mass (kg)［Scope of application］
Full size

Half size

Spacer

8.0

4.0

0.8

994 994 220 994 494 220 988 240 25

Vertical Permissible stressdirection Permissible stress78.5 kN/m²

Horizontal Permissible stressdirection Permissible stress30.0 kN/m²

30.0 kN/m²

for sustained loading

95%（2layer s or more）

Void ratio

Product name
Mass (kg)Vertical Permissible stressdirection Permissible stress［Scope of application］
Full size

Half size

Spacer

7.4

3.7

1.4

994 994 180 994 494 180 993 246 45
110.0 kN/m²

for sustained loading

40.0 kN/m²

Horizontal Permissible stressdirection Permissible stress26.5 kN/m²

for sustained loading

Void ratio

4

Can load a T-25 truck

CROSS-WAVE S
Dimension (mm)2.8m
or Under18.5 kN/m²

for sustained loading

CW-S

0.6m ‒
1.6m

0.5m‒
2.2m

less
than
4.0m

50.0 kN/m²
92%

Can load a T-25 truckHybrid structure (in the case of burial depth from 4.00m or more)

Ear t hc
0.5m overing
to 2.0m

CW-Ne
Burial depth
less than 4.0m

S
CW-N epth from
d
l
ia
Bu r
o 6.0m4.0m t※ The hybrid structure is applicable only to CW-Ne and CW-NS
・The dimensions above are ﬁgures under the temperature condition of 23 2 C.
・The ﬁgures showing mass above are those under standard speciﬁc gravity.

CW-Ne

CROSS-WAVE Ne［Scope of application］

Product name

Full size

Half size

Spacer

8.3

4.2

1.1

994 994 220 994 494 220 490 490 40

Dimension (mm)
Mass (kg)Vertical Permissible stressdirection Permissible stress110.0 kN/m²

Horizontal Permissible stressdirection Permissible stress60.0 kN/m²
26.5 kN/m²

for sustained loading

95%（3layer s or more）

Void ratio

Can load a T-25 truck

Maximum burial depth of 6.0m

［Scope of application］

CROSS-WAVE NS (For CW-Ne Hybrid)
Product nameDimension (mm)
Mass (kg)Full size

Half size

7.2

3.6
100.0 kN/m²

Horizontal Permissible stressdirection Permissible stress120.0 kN/m²

for sustained loading

Spacer994 994 160 994 494 160 490 490 40

Vertical Permissible stressdirection Permissible stressfor sustained loading

less
than
4.0m

36.0 kN/m²

for sustained loading

CW-NS

0.5m ‒
2.0m

36.0 kN/m²
54.0 kN/m²

1.1

0.5m ‒
2.0m

6.0m
or UnderCan load a T-25 truck5Structural Pattern and Installation Procedure

Two structural patterns offered according to the purpose:storage type and infiltration type
Simple structure makes installation easy and helps toshorten the work period.
■ Example structural patterns for storage type and inﬁltration typeThe following are example structural patterns of underground storage systems using CROSS-WAVE
according to the purpose.
Protective sheet
Permeable sheet

Storage
type

Impermeable sheet

Infiltration
type

Protective sheet

Depend on types of sheet, it can be adopted in both the storage type (left) and the inﬁltration type (right).

■ Installation
procedure①Digging②Spreading base gravel③Laying concrete slab

⑦Carrying in
CROSS-WAVE units⑥Laying innerprotective sheets⑤Laying impermeable
sheets④Laying outer
protective sheets⑧Piling up
CROSS-WAVE blocks⑨Installing spacers⑩Laying side andupper sheets

Storagetype
Inﬁltration
type⑪ Completed

Unlike concrete type, CROSS-WAVE does not require large-scale and prolonged construction work for installation, curing,etc. After the foundational construction (spreading base gravel, base concrete placing, etc.), the work that needs to bedone is only laying sheets, assembling CROSS-WAVE blocks and backﬁlling, minimizing work using heavy equipment, a
special-purpose vehicle, etc. to reduce costs.

6

Maintenance of the Inside of Storage Reservoirs

Thoughtful design for easy maintenance to operate safely
for a long time with peace of mind
In case of a ﬂood, Regular maintenance is needed. To prevent CROSS-WAVEʼs performance degradation fromearth and sand accumulated inside the storage reservoir due to rainwater inﬂow, a concrete managementbasin system for maintenance and an easy cleaning system are prepared. These make periodic inspection
and cleaning of deposition easy and quick, allowing full preparation for disasters.

Concretemanagementbasin system

A maintenance-focused storage reservoir structure
adopted Responding to small to large areas

Installing a sand basin, etc. at the inﬂow portion separates sand and earth ﬂowing in,thereby letting only rainwater enter the CROSS-WAVE storage reservoir. Maintenance canbe performed by removing deposition in the sand basin with a vacuum cleaner, etc.

Example of integrated inﬂow andoutﬂow basins

Example of separately locatinginﬂow and outﬂow basins
Outﬂow
basin

Inspection
hole
Inﬂow

Outﬂow

CROSS-WAVE

OriﬁceInspection
hole

CROSS-WAVE

Inspection
hole
Inﬂow
basin

Outﬂow
OriﬁceDeposited sand

Example of integrated inﬂow andoutﬂow basins(large-scale regulating pondage)
Inspection
hole

CROSS-WAVE

Inﬂow
Deposited
sand

Inﬂow

OriﬁceOutﬂow

Easy cleaningsystemDepositedsand

Thoughtfully designed for workers to enter throughthe inspection hole and do the cleaning easily
Workers can enter the CROSS-WAVE storage reservoir through the inspection hole tocheck the status of deposition in it. The easy cleaning system allows concentration of sandand earth ﬂowing in from the inﬂow pipe to deposit inside the basin, which can be checked
by workers.

7

Latest Installation Cases

Installation cases show CROSS-WAVEʼs capabilities.
Small- to large-scale facilities installed almost everywherein Japan
CROSS-WAVE has been used in more than 97% of prefecturesin Japan.
In other words, CROSS-WAVE has penetrated into almost allareas of the country.
Below are installation cases by architecture type, such as
plant, shopping center, warehouse, school, hospital andresidential area, that respond to various site environments
and installation conditions.

SchoolHospital

Plant andwarehouse

Publicfacility

Commercial
facility

Others■ Installation cases

Farm in Shizuoka Prefecture
16,500m³

Rainwater regulating reservoir
in Ishikawa Prefecture
9,200m³

Cemetery in Tokyo
1,000m³

Land development in
Okinawa Prefecture
400m³
Hospital in Saitama
Prefecture
110m³

8

□ Related products
Material for temporary roads “Plaroad”

Material exclusive for roads “AQUAROAD”
Construction Technology Review
and Certiﬁcation No.1012
Public Works Research Center

NETIS registration
Registration No.
KT-100053-VR

In the case of electric transmission-related construction work andcivil engineering work at paddies and ﬁelds, temporary roads are
traditionally constructed by using a combination of mountain sand,broken stones, crossties, etc. and steel plates; however, this method
makes the construction period longer and causes a problem withrestoration to the original state and material waste disposal. The
material for temporary roads named “Plaroad” enables eﬀective
construction and removal of temporary roads.

▲Flooding-prone roads, underpasses

Measures against soft ground/buoyant ▶
force, lightweight mounding“AQUAROAD” is eﬀective for load alleviation and as a measure against
ﬂooding in the event of concentrated heavy rain and buoyant force
when using earth pressure-relieving mounding and lightweightmounding. As a structural part of resin rainwater storage/inﬁltration
reservoirs that can be constructed under roads, AQUAROAD has
been certiﬁcated by Construction Technology Review and Public
Works Research Center.

Elementary school in Fukuoka
Prefecture 800m³

Commercial complex in
Saitama Prefecture
500m³

Housing land developmentin Saitama Prefecture 5m³

Elementary schoolin Chiba Prefecture

Commercial complex in Chiba
Prefecture 100m³

460m³

Town development in Saitama
Prefecture 15m³×140 subdivisions

9Reference

Live load (kN/m 2)

Total (kN/m 2)

Item

Scope of application(in the case of T-25)

T-25 T-20 T-14 T-25 T-20 T-14

Soil texture
Mass per unit volume (kN/m 3)
Coefficient of Coulombʼs earthpressure (Under 4.0 m)

9.0 78.8 63.1 44.2 87.8 72.1 53.2

Coefficient of earth pressure atrest (4 m min.)Burial depth (m)0.9 16.2 47.3 37.9 26.5 63.5 54.1 42.7
1.0 18.0 43.0 34.4 24.1 61.0 52.4 42.1
1.1 19.8 39.4 31.6 22.1 59.2 51.4 41.9
1.2 21.6 36.4 29.1 20.4 58.0 50.7 42.0
1.3 23.4 33.8 27.1 19.0 57.2 50.5 42.4
1.4 25.2 31.6 25.3 17.7 56.8 50.5 42.9

1.0

1.5

CW-HD
Permissible stress78.5 kN/m 2
Permissible stressforsustained loading
30 kN/m 2

1.5 27.0 29.6 23.7 16.6 56.6 50.7 43.6
1.6 28.8 27.9 22.3 15.6 56.7 51.1 44.4
1.7 30.6 26.3 21.1 14.8 56.9 51.7 45.4
1.8 32.4 24.9 20.0 14.0 57.3 52.4 46.4
1.9 34.2 29.6 23.7 16.6 63.8 57.9 50.8
2.0 36.0 28.2 22.6 15.8 64.2 58.6 51.8
2.1 37.8 26.9 21.5 15.1 64.7 59.3 52.9
2.2 39.6 25.7 20.6 14.4 65.3 60.2 54.0

2.0

CW-Ne
Permissible stress 110 kN/m 2
Permissible stress forsustained loading 36 kN/m 2
CW-NS
Permissible stress 100 kN/m 2
Permissible stress forsustained loading 36 kN/m 2

2.1

3.0

9.70

9.91

14.55

13.21 19.40

13.87 20.37
15.19 22.31

16.52 24.26

17.18 25.23

17.84 26.20
19.16 28.14

19.82 29.11

21.14 31.05

22.46 32.99

23.12 33.96

23.78 34.93

3.7

24.44 35.90

3.9

25.76 37.84

4.7

25.10 36.87

37.80 45.36

38.70 46.44

39.60 47.52

40.50 48.60
41.40 49.68

42.30 50.76

5.0

45.00 54.00

44.10 52.92

45.90 55.08

5.2

46.80 56.16

5.4

48.60 58.32

5.6

50.40 60.48

5.8

52.20 62.64

6.0

54.00 64.80

5.3
5.5
5.7

5.9

CW-Ne
Permissible stress<Normal> 60 kN/m 2<In the event of anearthquake> 78 kN/m 2
Permissible stress forsustained loading
26.5 kN/m 2

36.90 44.28

43.20 51.84

5.1

CW-S
Permissible stress<Normal> 50 kN/m 2<In the event of anearthquake> 65 kN/m 2
Permissible stress forsustained loading
26.5 kN/m 2

36.00 43.20

4.8
4.9

CW-HD
Permissible
stress<Normal>
30 kN/m 2<In the event ofan earthquake>
39 kN/m 2
Permissible
stress forsustainedloading
18.5 kN/m 2

18.50 27.17

21.80 32.02

4.6

Earth pressure at rest

6.61

CROSS-WAVE
Scope of application(in the case of cohesive soil)

Horizontal earth pressure(kN/m 2)

3.3

3.2

4.5

3.1 55.8 18.5 14.8 10.4 74.3 70.6 66.2

0.6
020.48 30.08

4.4

3.0 54.0 19.1 15.3 10.7 73.1 69.3 64.7

0.5

3.1

4.3

2.9 52.2 19.7 15.8 11.1 71.9 68.0 63.3

* The maximum earth covering is determined based on the long-term vertical load
performance test.

2.9

4.2

2.8 50.4 20.4 16.4 11.5 70.8 66.8 61.9

9.8 76.8 73.4 69.2

2.8

4.1

2.7 48.6 21.2 16.9 11.9 69.8 65.5 60.5

3.3 59.4 17.4 14.0

2.7

4.0

2.6 46.8 21.9 17.6 12.3 68.7 64.4 59.1

3.2 57.6 18.0 14.4 10.1 75.6 72.0 67.7

2.6

3.8

2.5 45.0 22.8 18.2 12.8 67.8 63.2 57.8

None

15.85 23.28

3.6

2.4 43.2 23.7 19.0 13.3 66.9 62.2 56.518
18
0.367 0.539

2.4

2.5

3.5

2.3 41.4 24.7 19.7 13.8 66.1 61.1 55.2

Cohesive soil Cohesive soil

14.53 21.34

3.4

CW-S
Permissible stress 110 kN/m 2
Permissible stress for sustained
loading 40 kN/m 2

In the event ofan earthquake*

2.2
2.3

Coulomb's earth pressure

0.8 14.4 52.6 42.1 29.5 67.0 56.5 43.9

Maximum earth covering 1.6 m

0.7 12.6 59.1 47.3 33.1 71.7 59.9 45.7
Maximum earth covering 2.0 m

Surcharge load (kN/m 2)

Maximum earth covering 2.2 m

0.6 10.8 67.6 54.1 37.9 78.4 64.9 48.7

NormalBurial depth 2.8 m max.

0.5

Verticalearth
load(kN/m2)scope of application of each product

Burial depth under 4.0 m

Earthcovering(m)■ Calculated load for the horizontal direction and

Burial depth under 4.0 m

application

Burial depth 6.0 m max.

■ Calculated load for the vertical direction and scope of

CW-NS
Permissible stress<Normal> 120 kN/m 2<In the event of an earthquake>
156 kN/m 2
Permissible stress for sustained
loading
54 kN/m 247.70 57.24

49.50 59.40
51.30 61.56

53.10 63.72* Calculated assuming that the design horizontal seismic coeﬃcient is 0.2

10■ Height and void ratio chart
Product
name

CW-HD

CW-S

CW-Ne+ NS

CW-Ne(in the case of hybrid)

No. oflayersHeight(m)

Void ratio(%)

Height(m)

Void ratio(%)

Height(m)

Void ratio(%)

Height
(m)

1

0.220

94

0.1800

92

0.230

94

1

0.230

2

0.405

94

0.2925

92

0.430

94

2

0.430

3

0.590

95

0.4050

92

0.630

95

3

0.630

4

0.775

95

0.5175

92

0.830

95

4

0.830

5

0.960

95

0.6300

92

1.030

95

5

1.030

6

1.145

95

0.7425

92

1.230

95

6

1.230

7

1.330

95

0.8550

92

1.430

95

7

1.430

8

1.515

95

0.9675

92

1.630

95

8

1.630

9

1.700

95

1.0800

92

1.830

95

9

1.830

10

1.885

95

1.1925

92

2.030

95

10

2.030

11

2.070

95

1.3050

92

2.230

95

11

2.230

12

2.255

95

1.4175

92

2.430

95

12

2.430

13

2.440

95

1.5300

92

2.630

95

13

2.630

14

1.6425

92

2.830

95

14

2.830

15

1.7550

92

3.030

95

15

3.030

16

1.8675

92

3.230

95

16

3.230

17

1.9800

92

3.430

95

17

3.430

18

2.0925

92

3.630

95

1

0.140

19

2.2050

92

2

0.280

20

2.3175

92

3

0.420

21

2.4300

92

4

0.560

22

2.5425

92

5

0.700

23

2.6550

92

6

0.840

24

2.7675

92

7

0.980

25

2.8800

92

8

1.120

26

2.9925

92

9

1.260

27

3.1050

92

10

1.400

28

3.2175

92

11

1.540

29

3.3300

92

12

1.680

30

3.4425

92

13

1.820

31

3.5550

92

14

1.960

32

3.6675

92

15

2.100

Range witha burial
depth under
4.0 m
CW-Ne isused.

Range witha burial
depth from
4.0 to 6.0 m
CW-NS isused.

Void ratio
(%)

94

95

94

■ Hybrid structure examples (CW-Ne + CW-NS)
Burial depth (m)Under 4 m
4 m min.

Product name

Plane area (m2)

No. of layers

CW-NS

Void ratio (%)

Storage volume (m3)0.500

Earth covering

CW-Ne

Height (m)

1,000

Total

17

3.430

95

3,258 ＊1

14

1.960

94

1,842 ＊1

31

5.890

5,100

*1: Figure after being rounded down to the nearest integer

11Our partner companies across Japan
provide support for design andinstallation throughout Japan.
Our partner company will provide support about the desired rainwater
storage reservoir (rainwater storage and inﬁltration facility), fromdesign consultation to after-sales service.

Designconsultation

Inquiry

Drawing creation
with CAD

Conﬁrmation
before installation

Assembly andinstallation

Installation
completion※ The support described above is provided upon request.

［To use CROSS-WAVE safely］

Below are important instructions regarding safety. Please be sure to follow them.
The following acts are prohibited as they may cause an accident or damage
to a facility.

Prohibition■Use of broken products
Never use broken products.

■Use near ﬁre

The products are ﬂammable. Keep away from ﬂames during storage andinstallation.

■Modiﬁcation of products

Do not make modiﬁcations (boring, cutting, etc.) to the products. Doing so
will reduce strength.

■Violation of law

Observe related laws, regulations, etc. for installation.

■Use outside the applicable scope

When using the products, observe the applicable loading condition by
product.(If the products are used with an earth covering, burial depth,
etc. outside the scope of application, the products may break.)■Crane operation

Do not operate a crane or remove sheet piles on the storage reservoir.

■Installation during stormy weather
Do not lay sheets during the rain or snow.

■Pouring of hot water

Pouring hot water will cause deformation and reduce strength. Contact
us before doing so.

To install products safely, caution should be
exercised regarding the following matters.

Caution■Handling products

Do not throw away the products. Doing so
will cause breakage.

■Storing products

When the products are in storage for a longtime, cover them with sheets to keep fromdirect sunlight.

■Laying sheets

Sheets shall be laid by professionals so as nott o c a u s e l e a k a g e o f w a t e r, e t c . d u e t oimperfect bonding of sheets.

■Installation

When getting on the upper surfaces of the
products or spacers during installation, watch
your step.

■Backﬁll

After completing installation of the storage
reservoir, backﬁll the hole as soon as possible.
Backﬁll the area around the storage reservoir
evenly so as not to cause uneven load.

■Oil resistanceIf organic solvents, oil, etc. stick to the
products, deformation and strength reduction
are caused. Be sure to keep them away.

※ SEKISUI CHEMICAL CO., LTD. makes a proposal pursuant to the Technical Guidelines for Plastic Underground Storage and Inﬁltration Facilities (Draft).

SEKISUI CHEMICAL CO., LTD.
URBAN INFRASTRUCTURE & ENVIRONMENTAL
PRODUCTS COMPANY
Pipe Systems & Civil Engineering Materials Sales Department.
Cross-wave Group

Eastern Japan
Okura Prestige Tower, 2-10-4 Toranomon, Minato-ku,
Tokyo 105-8566
Tel: +81-3-6626-2750 Fax: +81-3-6626-2752●

Central Japan / Western Japan
Dojima Kanden Building, 2-4-4 Nishitemma,
Kita-ku, Osaka 530-8565
Tel: +81-6-6365-4230 Fax: +81-6-6365-4356●

CROSS-WAVE Special Site

https://sekisui-cw.co.jp
2404C-E3